有没有办法让Java中的普通数组不可变？

[英]Is there any way to make an ordinary array immutable in Java?

本文翻译自 yak 查看原文 2013/06/15 8545 java/ arrays

Googled for it, found plenty of code. But any of them gave me what I want. I want to make an ordinary array Immutable. I tried this:

用Google搜索，找到了大量的代码。但是他们中的任何一个都给了我想要的东西。我想制作一个普通的数组永恒。我试过这个：

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class test {

    public static void main(String[] args) {

        final Integer array[];

        List<Integer> temp = new ArrayList<Integer>();
        temp.add(Integer.valueOf(0));
        temp.add(Integer.valueOf(2));
        temp.add(Integer.valueOf(3));
        temp.add(Integer.valueOf(4));
        List<Integer> immutable = Collections.unmodifiableList(temp);

        array = immutable.toArray(new Integer[immutable.size()]);

        for(int i=0; i<array.length; i++)
            System.out.println(array[i]);

        array[0] = 5;

        for(int i=0; i<array.length; i++)
            System.out.println(array[i]);

    }
}

But it doesnt work, I CAN assign a 5 into array[0] ... Is there any way to make this array immutable?

但它不起作用，我可以将5分配给数组[0] ...有没有办法使这个数组不可变？

3 个解决方案

#1

If you want to use it as an array, you can't.

如果要将其用作数组，则不能。

You have to create a wrapper for it, so that you throw an exception on, say, .set(), but no amount of wrapping around will allow you to throw an exception on:

你必须为它创建一个包装器，这样就可以在.set（）上抛出一个异常，但是没有任何包装可以让你在以下方面抛出异常：

array[0] = somethingElse;

Of course, immutability of elements is another matter entirely!

当然，元素的不变性完全是另一回事！

NOTE: the standard exception to throw for unsupported operations is aptly named UnsupportedOperationException; as it is unchecked you don't need to declare it in your method's throws clause.

注意：抛出不支持的操作的标准异常恰当地命名为UnsupportedOperationException;因为它未经检查，所以您不需要在方法的throws子句中声明它。

#2

It's impossible with primitive arrays.

原始数组是不可能的。

You will have to use the Collections.unmodifiableList() as you already did in your code.

您必须像在代码中一样使用Collections.unmodifiableList（）。

#3

You can also use Guava's ImmutableList, a high-performance, immutable, random-access List implementation that does not permit null elements. Unlike Collections.unmodifiableList(java.util.List), which is a view of a separate collection that can still change, an instance of ImmutableList contains its own private data and will never change.

您还可以使用Guava的ImmutableList，这是一种高性能，不可变的随机访问List实现，不允许使用null元素。与Collections.unmodifiableList（java.util.List）不同，Collections.unmodifiableList（java.util.List）是一个可以更改的单独集合的视图，ImmutableList的实例包含其自己的私有数据，并且永远不会更改。

注意！

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