How do I concatenate static string arrays [duplica

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Closed 7 years ago.

Possible Duplicate:
How to concatenate two arrays in Java?

I have SET1 declared as a static String[] and I would like to declare SET2 as SET1 + few other parameters. Is it possible to declare SET2 statically similar (i.e. private static String[]) to SET1 but using the above definition, if not how to do this?

private static final String[] SET1 = { "1", "2", "3" };

SET2 = SET1 + { "4", "5", "6" };

Answer 1

private static final String[] SET1 = { "1", "2", "3" };
private static final String[] SET2;

static
{
    List<String> set2 = new ArrayList<String>(Arrays.asList(SET1));
    set2.addAll(Arrays.asList("3", "4", "5"));
    SET2 = set2.toArray(new String[0]);
}

Answer 2

Maybe lists are easier in this case since arrays are fixed in length (by nature). You could do something like this if you want to instantiate it statically.

private static final List<String> SET1 = new ArrayList<String>();
private static final List<String> SET2 = new ArrayList<String>();
static {
    SET1.add("1");
    SET1.add("2");
    SET2.addAll(SET1);
    SET2.add("3");
}

Or use some kind of Collection utility library.

Answer 3

Look at Commons Util ArrayUtils.add:

static String[] SET2 = ArrayUtils.add(SET1, {"4", "5", "6" });

Answer 4

It's a big ugly:

private static final String[] SET1 = { "1", "2", "3" };
private static final String[] SET2 = concat(
    String.class, SET1, new String[]{"4", "5", "6"});

@SuppressWarnings("unchecked")
static <T> T[] concat(Class<T> clazz, T[] A, T[] B) {
    T[] C= (T[]) Array.newInstance(clazz, A.length+B.length);
    System.arraycopy(A, 0, C, 0, A.length);
    System.arraycopy(B, 0, C, A.length, B.length);
    return C;
 }