Javaでは配列のサイズを変更するために、我々は、所望の大きさの別の配列に全体元の配列をコピーします.

public class ReSizeArray{
	public int[] reSize(int[] a, int size){
		int[] temp = new int [size];
		System.arraycopy(a, 0, temp, 0, (a.length < size) ? a.length : size);
		return temp;
	}
	public void outPut(int[] a){
		for (int i=0; i<a.length; i++)
			System.out.print(a[i]+"  ");
	}
	public static void main(String [] agrs){
		ReSizeArray ns = new ReSizeArray();
		int[] a = new int[5];
		for (int i=0; i<a.length; i++)
			a[i] = i;
		System.out.println("nBefor change length of a = " + a.length);
		ns.outPut(a);
		a = ns.reSize(a, 20);
		for (int i=5; i<a.length; i++)
			a[i] = i;
		System.out.println("nAfter change length of a = " + a.length);
		ns.outPut(a);
	}
}