Best way to create singleton array

Question

What is the "easiest" way for you to create a singleton (with exactly one element) Objects array in Java ?

Answer 1

The standard way is this:

String[] arr = new String[]{"I am the one and only"};

I'm afraid it doesn't get much simpler than this.

Edit: it does:

String[] arr = {"I am the one and only"};

Thanks aioobe, I keep forgetting this.

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Of course if you often create array you can create a helper method that makes things a bit simpler:

public static <T> T[] asArray(T... items){
    return items;
}

String[] arr = asArray("I am the one and only");

(But you can't enforce at compile time that it will be an array with only one element)

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Next I was going to write a singleton array method, but Stephen beat me to that.

Answer 2

Object [] singleton = { new SomeObject() };

Answer 3

This should do the job

public SomeType[] makeSingletonArray(SomeType elem) {
    return new SomeType[]{elem);
}

A generic version of this method would be somewhat awkward to use, since you would need to pass it a Class object as an additional parameter.

Inlining the SomeType[]{elem} expression is simpler, and that's how I'd normally do this.

Answer 4

You could do this:

String[] a = Collections.singletonList("SingleElement").toArray();

Edit: Whoops! The above example doesn't compile. As stated in the comment, this can be done either as:

Object[] a = Collections.singletonList("SingleElement").toArray();
Or
String[] a = Collections.singletonList("SingleElement").toArray(new String[1]);

Answer 5

enum solution(anti reflect attack):

enum MySingleton{
    INSTANCE(new String[]{"a","b"});

    final String[] values;

    private MySingleton(String[] values) {
        this.values = values;
    }
}

reference it as:

MySingleton.INSTANCE;