英文:
Why are Java functions able to return local arrays?
问题
只是我注意到的一点：在C语言中，例如，如果您在函数内部有一个局部数组
*int returnArr() {
int arr[5] = {0};
return arr;
}
显然，这将无法编译。C语言会告诉您尝试返回局部变量。然而在Java中，同样的操作可以执行...
int[] returnArr() {
int[] arr = new int[5];
return arr;
}
而且这不会引起任何问题？为什么会这样？为什么Java可以做到，而C却不行？
英文:
Just something I noticed: In C, for example, if you have a local array inside a function
*int returnArr() {
int arr[5] = {0};
return arr;
}
Obviously this will not compile. C will tell you that you're trying to return a local variable. Yet in Java, the same can be done...
int[] returnArr() {
int[] arr = new int[5];
return arr;
}
and it causes no problems? Why is this? Why can Java do it but C can't?
答案1
得分: 6
你展示的两个代码片段实际上并不完全等价。在Java中，所有数组都是动态分配的（在堆上），而不是像在C中那样作为'函数局部'（在栈上）创建。
与您的Java代码最接近的C代码将是使用malloc()或calloc()函数（后者包含您的= {0}初始化）。
因此，以下代码是可以的（但您需要在某个时刻'手动'使用free()来释放内存，以模拟Java中的垃圾回收器）：
int *returnArr() {
int* arr = calloc(5, sizeof(int)); // "calloc"初始化为零
return arr;
}
英文:
The two code snippets you show aren't really equivalent. In Java, all arrays are dynamically allocated (on the heap), rather than being created as 'function local' (on the stack).
The C code most nearly equivalent to your Java code would be to use either the malloc() or calloc() function (the latter to incorporate your = {0} initialization).
Thus, the following would be fine (but you would have to 'manually' release the memory using free() at some point, to emulate the Garbage Collector that Java has):
int *returnArr() {
int* arr = calloc(5, sizeof(int)); // "calloc" initializes to zero
return arr;
}
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论