Example of implementing merge sort.

MergeSort.java

import java.util.*;

public class MergeSort
{
	public int[] a;

	public MergeSort()
	{
		a = new int[] { 0, 6, 41, 54, 57, 874, 243, 324, 1, 23, 4, 69, 7, 104 };
	}

	public void mergesort( int lo, int hi )
	{
		if( lo < hi ) {
			int m = (lo+hi)/2;
			mergesort( lo, m );
			mergesort( m+1, hi );
			merge( lo, hi, m );
		}
	}

	public void merge( int lo, int hi, int m )
	{
		int[] b = new int[a.length];

		for( int i = 0; i < a.length; i++ )
			b[i] = a[i];

		int i = lo;
		int j = m+1;
		int k = lo;

		while( i <= m && j <= hi ) {
			if( b[i] <= b[j] )
				a[k++] = b[i++];
			else
				a[k++] = b[j++];
		}

		while( i <= m )
			a[k++] = b[i++];

		System.out.println( Arrays.toString( a ));
	}

	public static void main( String[] args )
	{
		MergeSort ms = new MergeSort();
		ms.mergesort( 0, ms.a.length - 1 );
	}
}