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

问题描述

我是Java的新手，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.

我有一个A类例如 -

I have a class A for example -

A[] arr = new A[4];

但这只是创建指向A而不是4个对象的指针。它是否正确？我看到，当我尝试访问函数/变量在对象创建我得到一个空指针异常。
为了能够操作/访问对象，我必须这样做 -

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？如果这是正确的它真的奇怪。

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

编辑：我发现这是奇怪的，因为在C + +你只是说新的A [4]，它创建了四个对象。 >

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，与执行此操作类似

creates 4 A references, similar to doing this

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

现在你不能做a1.someMethod
$ b

now you couldn't do a1.someMethod() without allocating a1 as

a1 = new A();

同样，你需要做的数组

a[0] = new A();

。

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