Defining my own immutable array in Java

问题:

I know that declaring an array final does not make it immutable.

I can however define a wrapper class that functions like an immutable array, e.g.

public class ImmutableIntArray {
    private int[] array;

    public ImmutableIntArray(int[] array) {
        this.array = (int []) array.clone();
    }

    public int get(int i) {
        return array[i];
    }

    public int length() {
        return array.length;
    }

    public static void main(String[] args) {
        ImmutableIntArray a = new ImmutableIntArray(new int[]{1, 2, 3});

        for (int i = 0; i < a.length(); ++i)
            System.out.println(a.get(i));
    }
}

This approach seems elegant to me, however, it seems like quite an obvious approach that I'm surprised I haven't seen anyone else apply it. Why shouldn't this be for example part of a standard library somewhere? Am I making any mistakes about this definition, so that my class is in fact mutable?

I believe the same approach would work for any Object which is immutable, that I could even define it using generics, i.e. an ImmutableArray<T> class.

回答1:

You are reinventing the wheel. You can have the same result using Collections#unmodifiableList(..).

Collections.unmodifiableList(Arrays.asList(yourArray));