在 Java 中创建对象数组 [英] Creating an array of objects in Java

问题描述

我是 Java 新手，当时我在 Java 中创建了一个对象数组.

I am new to Java and for the time created an array of objects in Java.

例如我有一个 A 类 -

I have a class A for example -

A[] arr = new A[4];

但这只是创建指向 A 的指针(引用)而不是 4 个对象.这样对吗?我看到当我尝试访问创建的对象中的函数/变量时，我得到了一个空指针异常.为了能够操作/访问我必须这样做的对象:

But this is only creating pointers (references) to A and not 4 objects. Is this correct? I see that when I try to access functions/variables in the objects created I get a null pointer exception. To be able to manipulate/access the objects I had to do this:

A[] arr = new A[4];
for (int i = 0; i < 4; i++) {
    arr[i] = new A();
}

这是正确的还是我做错了什么?如果这是正确的，那真的很奇怪.

Is this correct or am I doing something wrong? If this is correct its really odd.

我觉得这很奇怪，因为在 C++ 中你只需说 new A[4] 并创建四个对象.

I find this odd because in C++ you just say new A[4] and it creates the four objects.

推荐答案

这是正确的.

A[] a = new A[4];

...创建 4 个 A 引用，类似于这样做:

...creates 4 A references, similar to doing this:

A a1;
A a2;
A a3;
A a4;

现在你不能在不分配 a1 的情况下做 a1.someMethod() 像这样:

Now you couldn't do a1.someMethod() without allocating a1 like this:

a1 = new A();

同样，对于数组，您需要这样做:

Similarly, with the array you need to do this:

a[0] = new A();

...在使用之前.

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