使用和不使用`New`关键字定义数组之间有什么区别? [英] What is the difference between using and not using `New` keyword to define an array?

问题描述

看看这两个简单的程序:

Look at this two simple program :

程序1:

public class GenArray extends Applet {
    byte[] myArray  ={ (byte) 'M', (byte) 'o', (byte) 'd', (byte) 'e',
            (byte) '1' };
}

程序2:

public class GenArray extends Applet {
    byte[] myArray = new byte[5];
    {
        myArray[0]  =(byte) 'M';
        myArray[1]  =(byte) 'o';
        myArray[2]  =(byte) 'd';
        myArray[3]  =(byte) 'e';
        myArray[4]  =(byte) '1';
    }
}

我想知道在Program-1的最后一行中的 MyArray 和在Program-2的最后一行中的 MyArray 之间是否有区别?(有任何区别！)

I want to know if is there any difference between MyArray in the last line of Program-1 and MyArray in the last line of Program-2? (Any difference!)

推荐答案

在第二个程序中， {...} 不是数组定界符，它们是块定界符.在这种情况下，它们用于提供所谓的初始化块，该初始化块在实例化您的类的新实例时执行.

In your second program, the { ... } are not array delimiters, they are block delimetes; in this case they are used to give a so-called initializer block, which is executed when a new instance of your class is instantiated.

创建初始化数组的正确"方法是:

The "correct" way to create an initialized array is:

new byte[] { 1, 2, 3 };

在初始化引用，使用现有引用或将数组传递给方法时，都可以始终使用它:

This can be used always, both when the reference is initialized and when an existing reference is used or when the array is passed to a method:

byte[] myArray = new byte[] { 1, 2, 3 };    // OK
myArray = new byte[] { 4, 5, 6 };           // OK
anObject.someMethod(new byte[] { 7, 8, 9}); // OK

但是，第一种变体非常普遍，因此Java允许您在特定情况下将 new byte [] 部分保留为

However, the first variant is very common and therefore Java allows you to leave the new byte[] part out in that particular case:

byte[] myArray = { 1, 2, 3 };    // OK
myArray = { 4, 5, 6 };           // Does not compile
anObject.someMethod({ 7, 8, 9}); // Does not compile

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