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< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > main< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > () {< / span > < / span >
< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 定义变量，即：开辟一块内存空间，并将初始化值存储进去< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > num < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > =< / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > 10< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ;< / span > < / span >
< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 访问变量，即：访问变量在内存中对应的数据< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > printf< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " num = < / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > %d\n< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " < / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > , num);< / span > < / span >
< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 给变量赋值，即：给变量在内存中占据的内存空间存储数据< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > num < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > =< / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > 100< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ;< / span > < / span >
< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 访问变量，即：访问变量在内存中对应的数据< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > printf< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " num = < / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > %d\n< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " < / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > , num);< / span > < / span >
< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > return< / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > 0< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ;< / span > < / span >
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< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > }< / span > < / span > < / code > < / pre > < div class = "line-numbers-wrapper" aria-hidden = "true" > < span class = "line-number" > 1< / span > < br > < span class = "line-number" > 2< / span > < br > < span class = "line-number" > 3< / span > < br > < span class = "line-number" > 4< / span > < br > < span class = "line-number" > 5< / span > < br > < span class = "line-number" > 6< / span > < br > < span class = "line-number" > 7< / span > < br > < span class = "line-number" > 8< / span > < br > < span class = "line-number" > 9< / span > < br > < span class = "line-number" > 10< / span > < br > < span class = "line-number" > 11< / span > < br > < span class = "line-number" > 12< / span > < br > < span class = "line-number" > 13< / span > < br > < span class = "line-number" > 14< / span > < br > < span class = "line-number" > 15< / span > < br > < span class = "line-number" > 16< / span > < br > < span class = "line-number" > 17< / span > < br > < span class = "line-number" > 18< / span > < br > < / div > < / div > < ul > < li > 上述的这种方式也称为< code > 直接访问< / code > ；当然，既然有< code > 直接访问< / code > 的方式，必然有< code > 间接访问< / code > 的方式，如：< code > 指针< / code > 。< / li > < / ul > < div class = "important custom-block github-alert" > < p class = "custom-block-title" > IMPORTANT< / p > < p > < / p > < ul > < li > ① 我们通过< code > 变量名（普通变量）< / code > 访问内存中变量存储的数据，之所以称为< code > 直接访问< / code > 的方式，是因为对于我们写程序而言，我们无需关心如何根据内存地址去获取内存中对应的数据，也无需关系如何根据内存地址将数据存储到对应的内存空间，这些操作步骤都是< code > 编译器< / code > 帮助我们在底层自动完成的（自动化）。< / li > < li > ② 但是，我们也可以通过< code > 内存地址< / code > 去操作内存中对应的数据（手动化），这种方式就称为< code > 间接访问< / code > 的方式了，相对于< code > 直接访问< / code > 方式来说，要< code > 理解< / code > 的< code > 概念< / code > 和< code > 操作< / code > 的< code > 步骤< / code > 和之前< code > 直接访问< / code > 的方式相比，要复杂和麻烦很多，但是效率高。< / li > < / ul > < / div > < h2 id = "_3-2-内存地址和指针" tabindex = "-1" > 3.2 内存地址和指针 < a class = "header-anchor" href = "#_3-2-内存地址和指针" aria-label = "Permalink to "3.2 内存地址和指针"" > < / a > < / h2 > < ul > < li > 其实，在之前《数组》中，我们就已经讲解了< code > 内存地址< / code > 的概念了，即：操作系统为了更快的去管理内存中的数据，会将< code > 内存条< / code > 按照< code > 字节< / code > 划分为一个个的< code > 单元格< / code > ，并为每个独立的小的< code > 单元格< / code > ，分配< code > 唯一的编号< / code > ，即：< code > 内存地址< / code > ，如下所示：< / li > < / ul > < p > < img src = "/c/assets/4.DqDR6Thp.svg" alt = "" > < / p > < div class = "note custom-block github-alert" > < p class = "custom-block-title" > NOTE< / p > < p > < / p > < p > 有了内存地址，就能加快数据的存取速度，可以类比生活中的< code > 字典< / code > ，即：< / p > < ul > < li > ① 内存地址是计算机中用于标识内存中某个特定位置的数值。< / li > < li > ② 每个内存单元都有一个唯一的地址，这些地址可以用于访问和操作存储在内存中的数据。< / li > < / ul > < / div > < ul > < li > 对于之前的代码，如下所示：< / li > < / ul > < div class = "language-c vp-adaptive-theme line-numbers-mode" > < button title = "Copy Code" class = "copy" > < / button > < span class = "lang" > c< / span > < pre class = "shiki shiki-themes github-light github-dark vp-code" tabindex = "0" > < code > < span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > #include< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > < stdio.h> < / span > < / span >
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< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > main< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > () {< / span > < / span >
< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 定义变量，即：开辟一块内存空间，并将初始化值存储进去< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > num < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > =< / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > 10< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ;< / span > < / span >
< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > return< / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > 0< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ;< / span > < / span >
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< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > }< / span > < / span > < / code > < / pre > < div class = "line-numbers-wrapper" aria-hidden = "true" > < span class = "line-number" > 1< / span > < br > < span class = "line-number" > 2< / span > < br > < span class = "line-number" > 3< / span > < br > < span class = "line-number" > 4< / span > < br > < span class = "line-number" > 5< / span > < br > < span class = "line-number" > 6< / span > < br > < span class = "line-number" > 7< / span > < br > < span class = "line-number" > 8< / span > < br > < span class = "line-number" > 9< / span > < br > < / div > < / div > < ul > < li > 虽然，之前我们在程序中都是通过< code > 变量名（普通变量）< / code > 直接操作内存中的存储单元；但是，编译器底层还是会通过< code > 内存地址< / code > 来找到所需要的存储单元，如下所示：< / li > < / ul > < p > < img src = "/c/assets/5.BzSkS-4w.svg" alt = "" > < / p > < div class = "note custom-block github-alert" > < p class = "custom-block-title" > NOTE< / p > < p > < / p > < p > 通过< code > 内存地址< / code > 找到所需要的< code > 存储单元< / code > ，即：内存地址指向该存储单元。此时，就可以将< code > 内存地址< / code > 形象化的描述为< code > 指针👉< / code > ，那么：< / p > < ul > < li > ① < code > 变量< / code > ：命名的内存空间，用于存放各种类型的数据。< / li > < li > ② < code > 变量名< / code > ：变量名是给内存空间取一个容易记忆的名字，方便我们编写程序。< / li > < li > ③ < code > 变量值< / code > ：变量所对应的内存中的存储单元中存放的数据值。< / li > < li > ④ < code > 变量的地址< / code > ：变量所对应的内存中的存储单元的内存地址（首地址），也可以称为< code > 指针< / code > 。< / li > < / ul > < p > 总结：内存地址 = 指针。< / p > < / div > < ul > < li > < code > 普通变量< / code > 所对应的内存空间< code > 存储< / code > 的是< code > 普通的值< / code > ，如：整数、小数、字符等；< code > 指针变量< / code > 所对应的内存空间< code > 存储< / code > 的是另外一个变量的< code > 地址（指针）< / code > ，如下所示：< / li > < / ul > < p > < img src = "/c/assets/6.BPY9ZGed.svg" alt = "" > < / p > < div class = "note custom-block github-alert" > < p class = "custom-block-title" > NOTE< / p > < p > < / p > < p > 有的时候，为了方便阐述，我们会将< code > 指针变量< / code > 称为< code > 指针< / code > 。但是，需要记住的是：< / p > < ul > < li > 指针 = 内存地址。< / li > < li > 指针变量 = 变量中保存的是另一个变量的地址。< / li > < / ul > < p > 下文中提及的< code > 指针< / code > 都是< code > 指针变量< / code > ，不再阐述！！！< / p > < / div > < div class = "important custom-block github-alert" > < p class = "custom-block-title" > IMPORTANT< / p > < p > < / p > < p > 如果你观察仔细的话，你可能会发现< code > 指针变量< / code > 和< code > 普通变量< / code > 在内存中占据的存储空间是不一样的，那么到底是什么原因造成这样的结果？< / p > < / div > < h2 id = "_3-3-指针变量的定义" tabindex = "-1" > 3.3 指针变量的定义 < a class = "header-anchor" href = "#_3-3-指针变量的定义" aria-label = "Permalink to "3.3 指针变量的定义"" > < / a > < / h2 > < h2 id = "_3-4-指针的作用" tabindex = "-1" > 3.4 指针的作用 < a class = "header-anchor" href = "#_3-4-指针的作用" aria-label = "Permalink to "3.4 指针的作用"" > < / a > < / h2 > < ul > < li > 查询数据。< / li > < li > 存储数据。< / li > < li > 参数传递。< / li > < li > 内存管理。< / li > < / ul > < p > 在 Java 中， （ ） （ ） < / p > < h3 id = "向上类型转换-upcasting" tabindex = "-1" > 向上类型转换（ ） < a class = "header-anchor" href = "#向上类型转换-upcasting" aria-label = "Permalink to "向上类型转换（ ） > < / a > < / h3 > < p > 向上类型转换是将一个子类对象引用转换为父类对象引用。由于子类继承了父类的所有方法和属性，子类对象也包含父类对象的所有部分，因此这种转换是安全且隐式的。< / p > < p > < s
2024-08-08 11:22:11 +02:00
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > void< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > makeSound< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > () {< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > System.out.< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > println< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " Animal sound" < / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > );< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > }< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > }< / span > < / span >
< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > class< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > Dog< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > extends< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > Animal< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > {< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > void< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > makeSound< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > () {< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > System.out.< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > println< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " Bark" < / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > );< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > }< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > }< / span > < / span >
< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > public< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > class< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > Main< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > {< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > public< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > static< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > void< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > main< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > String< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > [] < / span > < span style = "--shiki-light:#E36209;--shiki-dark:#FFAB70;" > args< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ) {< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > Dog dog < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > =< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > new< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > Dog< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ();< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > Animal animal < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > =< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > dog; < / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // Upcasting, 隐式转换< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > animal.< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > makeSound< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (); < / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 输出： < / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > }< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > }< / span > < / span > < / code > < / pre > < div class = "line-numbers-wrapper" aria-hidden = "true" > < span class = "line-number" > 1< / span > < br > < span class = "line-number" > 2< / span > < br > < span class = "line-number" > 3< / span > < br > < span class = "line-number" > 4< / span > < br > < span class = "line-number" > 5< / span > < br > < span class = "line-number" > 6< / span > < br > < span class = "line-number" > 7< / span > < br > < span class = "line-number" > 8< / span > < br > < span class = "line-number" > 9< / span > < br > < span class = "line-number" > 10< / span > < br > < span class = "line-number" > 11< / span > < br > < span class = "line-number" > 12< / span > < br > < span class = "line-number" > 13< / span > < br > < span class = "line-number" > 14< / span > < br > < span class = "line-number" > 15< / span > < br > < span class = "line-number" > 16< / span > < br > < span class = "line-number" > 17< / span > < br > < span class = "line-number" > 18< / span > < br > < span class = "line-number" > 19< / span > < br > < / div > < / div > < p > 在这个例子中，< code > Dog< / code > 类型的对象 < code > dog< / code > 被转换为 < code > Animal< / code > 类型。尽管 < code > animal< / code > 引用的实际对象是 < code > Dog< / code > ，但在编译时，< code > animal< / code > 被视为 < code > Animal< / code > 类型。< / p > < h3 id = "向下类型转换-downcasting" tabindex = "-1" > 向下类型转换（ ） < a class = "header-anchor" href = "#向下类型转换-downcasting" aria-label = "Permalink to "向下类型转换（ ） > < / a > < / h3 > < p > 向下类型转换是将一个父类对象引用转换为子类对象引用。由于父类对象不一定具有子类的所有方法和属性，因此这种转换需要显式进行，并且在运行时进行类型检查（使用 < code > instanceof< / code > 关键字来确保安全）。< / p > < p > < strong > 例子：< / strong > < / p > < div class = "language-java vp-adaptive-theme line-numbers-mode" > < button title = "Copy Code" class = "copy" > < / button > < span class = "lang" > java< / span > < pre class = "shiki shiki-themes github-light github-dark vp-code" tabindex = "0" > < code > < span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > public< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > class< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > Main< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > {< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > public< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > static< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > void< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > main< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > String< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > [] < / span > < span style = "--shiki-light:#E36209;--shiki-dark:#FFAB70;" > args< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ) {< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > Animal animal < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > =< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > new< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > Dog< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (); < / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // Upcasting< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > if< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (animal < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > instanceof< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > Dog) {< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > Dog dog < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > =< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (Dog) animal; < / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // Downcasting, 显式转换< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > dog.< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > makeSound< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (); < / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 输出： < / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > }< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > }< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > }< / span > < / span > < / code > < / pre > < div class = "line-numbers-wrapper" aria-hidden = "true" > < span class = "line-number" > 1< / span > < br > < span class = "line-number" > 2< / span > < br > < span class = "line-number" > 3< / span > < br > < span class = "line-number" > 4< / span > < br > < span class = "line-number" > 5< / span > < br > < span class = "line-number" > 6< / span > < br > < span class = "line-number" > 7< / span > < br > < span class = "line-number" > 8< / span > < br > < span class = "line-number" > 9< / span > < br > < / div > < / div > < p > 在这个例子中，< code > animal< / code > 引用的对象实际是 < code > Dog< / code > 类型，在向下转换之前使用 < code > instanceof< / code > 检查以确保安全。< / p > < h3 id = "区别" tabindex = "-1" > 区别 < a class = "header-anchor" href = "#区别" aria-label = "Permalink to "区别"" > < / a > < / h3 > < ul > < li > < strong > 向上类型转换< / strong > ：隐式的，安全的，因为子类是父类的扩展。< / li > < li > < strong > 向下类型转换< / strong > ：显式的，可能不安全，需要运行时检查，因为父类不一定具有子类的特性。< / li > < / ul > < h3 id = "c-语言中的指针转换" tabindex = "-1" > C 语言中的指针转换 < a class = "header-anchor" href = "#c-语言中的指针转换" aria-label = "Permalink to "C 语言中的指针转换"" > < / a > < / h3 > < p > 在 C 语言中，指针的转换类似于引用类型的转换，但由于 C 语言没有继承和多态的概念，其转换更多是基于内存布局。< / p > < p > < strong > 例子：< / strong > < / p > < div class = "language-c vp-adaptive-theme line-numbers-mode" > < button title = "Copy Code" class = "copy" > < / button > < span class = "lang" > c< / span > < pre class = "shiki shiki-themes github-light github-dark vp-code" tabindex = "0" > < code > < span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > #include< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > < stdio.h> < / span > < / span >
< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > void< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > printInt< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > void*< / span > < span style = "--shiki-light:#E36209;--shiki-dark:#FFAB70;" > ptr< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ) {< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > printf< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " < / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > %d\n< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " < / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > , < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > *< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int*< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > )ptr);< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > }< / span > < / span >
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< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int< / span > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > main< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > () {< / span > < / span >
2024-08-08 11:22:11 +02:00
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > x < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > =< / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > 10< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ;< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > void*< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > voidPtr < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > =< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > & < / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > x;< / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // Upcasting, 隐式转换< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > printInt< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (voidPtr);< / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 输出： < / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > < / span > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int*< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > intPtr < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > =< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int*< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > )voidPtr;< / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // Downcasting, 显式转换< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > printf< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " < / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > %d\n< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " < / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > , < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > *< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > intPtr);< / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 输出： < / span > < / span >
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< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > return< / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > 0< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ;< / span > < / span >
2024-08-08 11:22:11 +02:00
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > }< / span > < / span > < / code > < / pre > < div class = "line-numbers-wrapper" aria-hidden = "true" > < span class = "line-number" > 1< / span > < br > < span class = "line-number" > 2< / span > < br > < span class = "line-number" > 3< / span > < br > < span class = "line-number" > 4< / span > < br > < span class = "line-number" > 5< / span > < br > < span class = "line-number" > 6< / span > < br > < span class = "line-number" > 7< / span > < br > < span class = "line-number" > 8< / span > < br > < span class = "line-number" > 9< / span > < br > < span class = "line-number" > 10< / span > < br > < span class = "line-number" > 11< / span > < br > < span class = "line-number" > 12< / span > < br > < span class = "line-number" > 13< / span > < br > < span class = "line-number" > 14< / span > < br > < span class = "line-number" > 15< / span > < br > < / div > < / div > < p > 在这个例子中，< code > void*< / code > 是通用指针类型，可以指向任何类型的数据。将 < code > int*< / code > 转换为 < code > void*< / code > 是隐式的，而将 < code > void*< / code > 转换为 < code > int*< / code > 是显式的。由于 C 没有类型检查，因此这种转换需要程序员自己确保安全。< / p > < p > 总结：< / p > < ul > < li > Java 中的向上类型转换和向下类型转换是为了支持多态性和继承，向上转换是安全的，向下转换需要显式进行并且进行运行时检查。< / li > < li > C 语言中的指针转换没有多态性和继承的概念，但有类似的指针类型转换操作，程序员需要确保转换的安全性。< / li > < / ul > < h1 id = "第四章-指针的运算-⭐" tabindex = "-1" > 第四章：指针的运算（⭐） < a class = "header-anchor" href = "#第四章-指针的运算-⭐" aria-label = "Permalink to "第四章：指针的运算（⭐）"" > < / a > < / h1 > < h2 id = "_4-1-概述" tabindex = "-1" > 4.1 概述 < a class = "header-anchor" href = "#_4-1-概述" aria-label = "Permalink to "4.1 概述"" > < / a > < / h2 > < h2 id = "_4-2-总结" tabindex = "-1" > 4.2 总结 < a class = "header-anchor" href = "#_4-2-总结" aria-label = "Permalink to "4.2 总结"" > < / a > < / h2 > < ul > < li > < p > 在 C 语言中，< code > 普通变量< / code > 是直接存储< code > 数据< / code > 的< code > 变量< / code > 。对于普通变量，支持的操作包括：< / p > < ul > < li > ① < strong > 赋值操作< / strong > ：给变量赋值，如：< code > int a = 5< / code > 。< / li > < li > ② < strong > 算术运算< / strong > ：可以对数值类型的普通变量进行加、减、乘、除等运算，如：< code > a + b< / code > 、< code > a - b< / code > 、< code > a * b< / code > 、< code > a / b< / code > < / li > < li > ③ < strong > 关系运算< / strong > ：可以进行比较运算（大于、小于、等于等），如： < code > a > b< / code > 、< code > a == b< / code > 。< / li > < li > ④ < strong > 逻辑运算< / strong > ：对布尔类型的值进行与、或、非运算，如： < code > a & & b< / code > 、< code > a || b< / code > 、< code > !a< / code > 。< / li > < li > ⑤ < strong > 位运算< / strong > ：对整数类型的值进行位操作（与、或、异或、取反、左移、右移等），如： < code > a & b< / code > 、< code > a | b< / code > 、< code > a ^ b< / code > 、< code > ~a< / code > 、< code > a < < 2< / code > 、< code > a > > 2< / code > 。< / li > < li > ⑥ < strong > 自增自减运算< / strong > ： < code > a++< / code > 、< code > --a< / code > 等。< / li > < / ul > < / li > < li > < p > 在 C 语言中，< code > 指针变量< / code > 存储的是< code > 另一个变量< / code > 的< code > 地址< / code > 。对于指针变量，支持的操作包括：< / p > < ul > < li > ① < strong > 赋值操作< / strong > ：可以将一个地址赋值给指针，如： < code > int *p = & a;< / code > 。< / li > < li > ② < strong > 解引用操作< / strong > ：通过指针访问它指向的变量，如： < code > *p = 10;< / code > 修改指向变量的值。< / li > < li > ③ < strong > 指针运算< / strong > ： < ul > < li > < strong > 指针和整数值的加减运算< / strong > ：指针可以进行整数的加减运算，用于访问数组或结构体成员，如： < code > p + 1< / code > 。< / li > < li > < strong > 指针的自增和自减运算< / strong > ：指的是内存地址的向前或向后移动，如：< code > p++< / code > 、< code > p--< / code > 。< / li > < li > < strong > 指针间的相减运算< / strong > ：两个指向同一数组的指针相减可以得到它们之间的元素个数，如
2024-07-31 03:20:24 +02:00
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > *< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ptr < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > =< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > arr;< / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 这句话是合法的， < / span > < / span >
< span class = "line" > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > printf< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " < / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > %p\n< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " < / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > , arr);< / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 打印数组名，会打印数组首地址< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > printf< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " < / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > %p\n< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " < / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > , < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > & < / span > < span style = "--shiki-light:#E36209;--shiki-dark:#FFAB70;" > arr< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > [< / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > 0< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ]);< / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 打印第一个元素的地址< / span > < / span > < / code > < / pre > < div class = "line-numbers-wrapper" aria-hidden = "true" > < span class = "line-number" > 1< / span > < br > < span class = "line-number" > 2< / span > < br > < span class = "line-number" > 3< / span > < br > < span class = "line-number" > 4< / span > < br > < / div > < / div > < / li > < li > < p > < strong > 数组名是常量指针< / strong > ： < / p > < div class = "language-c vp-adaptive-theme line-numbers-mode" > < button title = "Copy Code" class = "copy" > < / button > < span class = "lang" > c< / span > < pre class = "shiki shiki-themes github-light github-dark vp-code" tabindex = "0" > < code > < span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int< / span > < span style = "--shiki-light:#E36209;--shiki-dark:#FFAB70;" > arr< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > [< / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > 5< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ];< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > *< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ptr < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > =< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > arr;< / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 合法， < / span > < / span >
< span class = "line" > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ptr< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > ++< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ;< / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 合法， < / span > < / span >
< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // arr++; // 非法，编译错误，因为数组名是常量，不能改变< / span > < / span > < / code > < / pre > < div class = "line-numbers-wrapper" aria-hidden = "true" > < span class = "line-number" > 1< / span > < br > < span class = "line-number" > 2< / span > < br > < span class = "line-number" > 3< / span > < br > < span class = "line-number" > 4< / span > < br > < span class = "line-number" > 5< / span > < br > < / div > < / div > < / li > < li > < p > < strong > sizeof运算符的结果不同< / strong > ： < code > sizeof< / code > 运算符对数组名和指针变量会得到不同的结果，数组名会返回整个数组的大小，而指针变量会返回指针本身的大小。< / p > < div class = "language-c vp-adaptive-theme line-numbers-mode" > < button title = "Copy Code" class = "copy" > < / button > < span class = "lang" > c< / span > < pre class = "shiki shiki-themes github-light github-dark vp-code" tabindex = "0" > < code > < span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int< / span > < span style = "--shiki-light:#E36209;--shiki-dark:#FFAB70;" > arr< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > [< / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > 5< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ];< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > *< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ptr < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > =< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > arr;< / span > < / span >
< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > printf< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " sizeof(arr) = < / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > %lu\n< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " < / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > , < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > sizeof< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (arr));< / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 返回数组的大小， < / span > < / span >
< span class = "line" > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > printf< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " sizeof(ptr) = < / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > %lu\n< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " < / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > , < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > sizeof< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (ptr));< / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 返回指针的大小， < / span > < / span > < / code > < / pre > < div class = "line-numbers-wrapper" aria-hidden = "true" > < span class = "line-number" > 1< / span > < br > < span class = "line-number" > 2< / span > < br > < span class = "line-number" > 3< / span > < br > < span class = "line-number" > 4< / span > < br > < span class = "line-number" > 5< / span > < br > < / div > < / div > < / li > < li > < p > < strong > 地址运算符的结果不同< / strong > ： < code > & < / code > 对数组名和指针变量会得到不同的结果，对数组名使用< code > & < / code > 会返回数组的地址，而对指针变量使用< code > & < / code > 会返回指针变量本身的地址。< / p > < div class = "language-c vp-adaptive-theme line-numbers-mode" > < button title = "Copy Code" class = "copy" > < / button > < span class = "lang" > c< / span > < pre class = "shiki shiki-themes github-light github-dark vp-code" tabindex = "0" > < code > < span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int< / span > < span style = "--shiki-light:#E36209;--shiki-dark:#FFAB70;" > arr< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > [< / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > 5< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ];< / span > < / span >
< span class = "line" > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > int< / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > *< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > ptr < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > =< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > arr;< / span > < / span >
< span class = "line" > < / span >
< span class = "line" > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > printf< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " Address of array: < / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > %p\n< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " < / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > , < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > & < / span > < span style = "--shiki-light:#E36209;--shiki-dark:#FFAB70;" > arr< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > );< / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 返回整个数组的地址< / span > < / span >
2024-08-11 06:51:13 +02:00
< span class = "line" > < span style = "--shiki-light:#6F42C1;--shiki-dark:#B392F0;" > printf< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > (< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " Address of pointer: < / span > < span style = "--shiki-light:#005CC5;--shiki-dark:#79B8FF;" > %p\n< / span > < span style = "--shiki-light:#032F62;--shiki-dark:#9ECBFF;" > " < / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > , < / span > < span style = "--shiki-light:#D73A49;--shiki-dark:#F97583;" > & < / span > < span style = "--shiki-light:#E36209;--shiki-dark:#FFAB70;" > ptr< / span > < span style = "--shiki-light:#24292E;--shiki-dark:#E1E4E8;" > );< / span > < span style = "--shiki-light:#6A737D;--shiki-dark:#6A737D;" > // 返回指针变量ptr的地址< / span > < / span > < / code > < / pre > < div class = "line-numbers-wrapper" aria-hidden = "true" > < span class = "line-number" > 1< / span > < br > < span class = "line-number" > 2< / span > < br > < span class = "line-number" > 3< / span > < br > < span class = "line-number" > 4< / span > < br > < span class = "line-number" > 5< / span > < br > < / div > < / div > < / li > < / ol > < p > 综上所述，通过这些示例和解释，可以看出数组名虽然在某些场合下可以像指针一样使用，但它并不是一个真正的指针变量，而是一个常量，表示数组的首地址。< / p > < / div > < / div > < / main > < footer class = "VPDocFooter" data-v-39a288b8 data-v-e257564d > <!-- [ --> <!-- ] --> < div class = "edit-info" data-v-e257564d > <!-- --> < div class = "last-updated" data-v-e257564d > < p class = "VPLastUpdated" data-v-e257564d data-v-e98dd255 > 上次更新: < time datetime = "2024-08-11T04:50:40.000Z" data-v-e98dd255 > < / time > < / p > < / div > < / div > < nav class = "prev-next" aria-labelledby = "doc-footer-aria-label" data-v-e257564d > < span class = "visually-hidden" id = "doc-footer-aria-label" data-v-e257564d > Pager< / span > < div class = "pager" data-v-e257564d > < a class = "VPLink link pager-link prev" href = "/c/notes/01_c-basic/05_xdx/" data-v-e257564d > <!-- [ --> < span class = "desc" data-v-e257564d > 上一篇< / span > < span class = "title" data-v-e257564d > 数组< / span > <!-- ] --> < / a > < / div > < div class = "pager" data-v-e257564d > < a class = "VPLink link pager-link next" href = "/c/notes/01_c-basic/07_xdx/" data-v-e257564d > <!-- [ --> < span class = "desc" data-v-e257564d > 下一篇< / span > < span class = "title" data-v-e257564d > 函数< / span > <!-- ] --> < / a > < / div > < / nav > < / footer > <!-- [ --> <!-- ] --> < / div > < / div > < / div > <!-- [ --> <!-- ] --> < / div > < / div > < footer class = "VPFooter has-sidebar" data-v-5d98c3a5 data-v-e315a0ad > < div class = "container" data-v-e315a0ad > < p class = "message" data-v-e315a0ad > Released under the MIT License.< / p > < p class = "copyright" data-v-e315a0ad > Copyright © 2024 许大仙< / p > < / div > < / footer > <!-- [ --> <!-- ] --> < / div > < / div >
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< script > w i n d o w . _ _ V P _ H A S H _ M A P _ _ = J S O N . p a r s e ( " { \ " i n d e x . m d \ " : \ " n 0 W - F d - u \ " , \ " n o t e s _ 0 1 _ c - b a s i c _ 0 0 _ x d x _ i n d e x . m d \ " : \ " D S B f E d i 8 \ " , \ " n o t e s _ 0 1 _ c - b a s i c _ 0 1 _ x d x _ i n d e x . m d \ " : \ " e 0 L U V T X C \ " , \ " n o t e s _ 0 1 _ c - b a s i c _ 0 2 _ x d x _ i n d e x . m d \ " : \ " 0 G H s M M a 0 \ " , \ " n o t e s _ 0 1 _ c - b a s i c _ 0 3 _ x d x _ i n d e x . m d \ " : \ " C L v C g g 5 M \ " , \ " n o t e s _ 0 1 _ c - b a s i c _ 0 4 _ x d x _ i n d e x . m d \ " : \ " D k X f R s s o \ " , \ " n o t e s _ 0 1 _ c - b a s i c _ 0 5 _ x d x _ i n d e x . m d \ " : \ " C T O 1 N X P 8 \ " , \ " n o t e s _ 0 1 _ c - b a s i c _ 0 6 _ x d x _ i n d e x . m d \ " : \ " B 8 Z 5 K X t i \ " , \ " n o t e s _ 0 4 _ l i n u x _ 0 1 _ x d x _ i n d e x . m d \ " : \ " D 7 - U l H S H \ " , \ " n o t e s _ i n d e x . m d \ " : \ " b g N n s 6 d 1 \ " } " ) ; w i n d o w . _ _ V P _ S I T E _ D A T A _ _ = J S O N . p a r s e ( " { \ " l a n g \ " : \ " z h - C N \ " , \ " d i r \ " : \ " l t r \ " , \ " t i t l e \ " : \ " 许 大 仙 \ " , \ " t i t l e T e m p l a t e \ " : \ " H i ， 终 于 等 到 你 \ " , \ " d e s c r i p t i o n \ " : \ " 许 大 仙 前 端 、 J a v a 、 大 数 据 、 云 原 生 \ " , \ " b a s e \ " : \ " / c / \ " , \ " h e a d \ " : [ ] , \ " r o u t e r \ " : { \ " p r e f e t c h L i n k s \ " : t r u e } , \ " a p p e a r a n c e \ " : t r u e , \ " t h e m e C o n f i g \ " : { \ " l a s t U p d a t e d T e x t \ " : \ " 上 次 更 新 \ " , \ " r e t u r n T o T o p L a b e l \ " : \ " 返 回 顶 部 \ " , \ " s e a r c h \ " : { \ " p r o v i d e r \ " : \ " l o c a l \ " } , \ " l o g o \ " : \ " / l o g o . s v g \ " , \ " n a v \ " : [ { \ " t e x t \ " : \ " 首 页 \ " , \ " l i n k \ " : \ " h t t p s : / / a e x i a r . g i t h u b . i o / \ " } , { \ " t e x t \ " : \ " 计 组 6 件 套 \ " , \ " l i n k \ " : \ " h t t p s : / / a e x i a r . g i t h u b . i o / c o a 6 / n o t e s / \ " } , { \ " t e x t \ " : \ " 编 程 语 言 \ " , \ " i t e m s \ " : [ { \ " t e x t \ " : \ " c / c + + \ " , \ " l i n k \ " : \ " / n o t e s / \ " } , { \ " t e x t \ " : \ " 前 端 \ " , \ " l i n k \ " : \ " h t t p s : / / a e x i a r . g i t h u b . i o / w e b - d e s i g n / n o t e s / \ " } , { \ " t e x t \ " : \ " J a v a \ " , \ " l i n k \ " : \ " h t t p s : / / a e x i a r . g i t h u b . i o / j a v a / n o t e s / \ " } , { \ " t e x t \ " : \ " 大 数 据 \ " , \ " l i n k \ " : \ " h t t p s : / / a e x i a r . g i t h u b . i o / b i g - d a t a / n o t e s / \ " } , { \ " t e x t \ " : \ " 云 原 生 \ " , \ " l i n k \ " : \ " h t t p s : / / a e x i a r . g i t h u b . i o / l i n u x / n o t e s / \ " } , { \ " t e x t \ " : \ " G o \ " , \ " l i n k \ " : \ " h t t p s : / / a e x i a r . g i t h u b . i o / g o / n o t e s / \ " } , { \ " t e x t \ " : \ " P y t h o n \ " , \ " l i n k \ " : \ " h t t p s : / / a e x i a r . g i t h u b . i o / p y t h o n / n o t e s / \ " } ] } , { \ " t e x t \ " : \ " 开 源 软 件 \ " , \ " l i n k \ " : \ " h t t p s : / / a e x i a r . g i t h u b . i o / o p e n - s o f t w a r e / n o t e s / \ " } ] , \ " s i d e b a r \ " : { \ " / n o t e s / \ " : [ { \ " t e x t \ " : \ " C 语 言 基 础 \ " , \ " c o l l a p s e d \ " : t r u e , \ " i t e m s \ " : [ { \ " t e x t \ " : \ " 编 程 基 础 \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 0 0 _ x d x / \ " } , { \ " t e x t \ " : \ " C 语 言 入 门 \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 0 1 _ x d x / \ " } , { \ " t e x t \ " : \ " 变 量 和 进 制 \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 0 2 _ x d x / \ " } , { \ " t e x t \ " : \ " 数 据 类 型 和 运 算 符 \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 0 3 _ x d x / \ " } , { \ " t e x t \ " : \ " 流 程 控 制 \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 0 4 _ x d x / \ " } , { \ " t e x t \ " : \ " 数 组 \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 0 5 _ x d x / \ " } , { \ " t e x t \ " : \ " 指 针 \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 0 6 _ x d x / \ " } , { \ " t e x t \ " : \ " 函 数 \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 0 7 _ x d x / \ " } , { \ " t e x t \ " : \ " 预 处 理 器 \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 0 8 _ x d x / \ " } , { \ " t e x t \ " : \ " 自 定 义 数 据 类 型 \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 0 9 _ x d x / \ " } , { \ " t e x t \ " : \ " 字 符 串 和 时 间 \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 1 0 _ x d x / \ " } , { \ " t e x t \ " : \ " 内 存 管 理 \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 1 1 _ x d x / \ " } , { \ " t e x t \ " : \ " 文 件 操 作 \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 1 2 _ x d x / \ " } , { \ " t e x t \ " : \ " 调 试 工 具 和 调 试 技 巧 （ g d b 和 m a k e ） \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 1 3 _ x d x / \ " } , { \ " t e x t \ " : \ " 常 用 库 函 数 \ " , \ " l i n k \ " : \ " / n o t e s / 0 1 _ c - b a s i c / 1 4 _ x d x / \ " } ] } , { \ " t e x t \ " : \ " C 语 言 高 级 \ " , \ " c o l l a p s e d \ " : t r u e , \ " i t e m s \ " : [ { \ " t e x t \ " : \ " 变 量 和 内 存 分 布 \ " , \ " l i n k \ " : \ " / n o t e s / 0 2 _ c - a d v a n c e / 0 1 _ x d x / \ " } , { \ " t e x t \ " : \ " 指 针 强 化 \ " , \ " l i n k \ " : \ " / n o t e s / 0 2 _ c - a d v a n c e / 0 2 _ x d x / \ " } , { \ " t e x t \ " : \ " 结 构 体 和 文 件 的 高 级 用 法 \ " , \ " l i n k \ " : \ " / n o t e s / 0 2 _ c - a d v a n c e / 0 3 _ x d x / \ " } , { \ " t e x t \ " : \ " 链 表 和 回 调 函 数 \ " , \ " l i n k \ " : \ " / n o t e s / 0 2 _ c - a d v a n c e / 0 4 _ x d x / \ " } , { \ " t e x t \ " : \ " 编 译 过 程 和 面 向 接 口 \ " , \ " l i n k \ " : \ " / n o t e s / 0 2 _ c - a d v a n c e / 0 5 _ x d x / \ " } ] } , { \ " t e x t \ " : \ " 项 目 构 建 工 具 \ " , \ " c o l l a p s e d \ " : t r u e , \ " i t e m s \ " : [ { \ " t e x t \ " : \ " m e s o n \ " , \ " c o l l a p s e d \ " : t r u e , \ " i t e m s \ " : [ { \ " t e x t \ " : \ " G r a d l e 入 门 \ " , \ " l i n k \ " : \ " / n o t e s / 0 3 _ b u i l d / 0 1 _ x d x / \ " } ] } , { \ " t e x t \ " : \ " c m a k e \ " , \ " c o l l a p s e d \ " : t r u e , \ " i t e m s \ " : [ { \ " t e x t \ " : \ " G r a d l e 入 门 \ " , \ " l i n k \ " : \ " / n o t e s / 0 3 _ b u i l d / 0 1 _ x d x / \ " } ] } , { \ " t e x t \ " : \ " c o n a n \ " , \ " l i n k \ " : \ " / n o t e s / 0 3 _ b u i l d / 0 1 _ $ { c o m m o n D i r e c t o r y N a m e } / \ " } , { \ " t e x t \ " : \ " G r a d l e \ " , \ " c o l l a p s e d \ " : t r u e , \ " i t e m s \ " : [ { \ " t e x t \ " : \ " G r a d l e 入 门 \ " , \ " l i n k \ " : \ " / n o t e s / 0 3 _ b u i l d / 0 1 _ x d x / \ " } ] } ] } , { \ " t e x t \ " : \ " L i n u x \ " , \ " c o l l a p s e d \ " : t r u e , \ " i t e m s \ " : [ { \ " t e x t \ " : \ " L i n u x 初 识 和 安 装 \ " , \ " l i n k \ " : \ " / n o t e s / 0 4 _ l i n u x / 0 1 _ x d x / \ " } ] } , { \ " t e x t \ " : \ " C + + 核 心 编 程 \ " , \ " c o l l a p s e d \ " : t r u e , \ " i t e m s \ " : [ ] } , { \ " t e x t \ " : \ " C + + 标 准 库 \ " , \ " c o l l a p s e d \ " : t r u e , \ " i t e m s \ " : [ ] } , { \ " t e x t \ " : \ " Q T 桌 面 开 发 \ " , \ " c o l
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