This is the code implementing Merge Sort.

GenericMergeSort.java

import java.util.ArrayList;
import java.util.List;

public class Main {
    public static void main(String[] args) {
    if (args.length == 0) {
	    System.out
		    .println("Proper Usage is: java main number1 number2 number3 ...");
	    System.exit(0);
	}
	// <T extends Comparable<T>>
	List<String> list = new ArrayList<String>();
	    for (int i = 0; i < args.length; i++)
	        list.add(args[i]);
    	Main main = new Main();
    	main.print(list);
    	main.merge_sort(list, 0, args.length - 1);
    	main.print(list);
    }

    public <T> void print(List<T> array) {
	    print(array, 0, array.size() - 1);
    }

    public <T> void print(List<T> array, int start, int end) {
    	if (start > end || start < 0 || end > array.size() - 1)
    	    return;
    	for (int i = start; i <= end; i++) {
    	    System.out.print(array.get(i) + " ");
    	}
    	System.out.println();
    }

    public <T extends Comparable<T>> void merge_sort(List<T> array, int start,
	    int end) {
    	// print(array, start, end);
    	if (end == start)
    	    return;
    
    	int mid = (start + end) / 2;
    	merge_sort(array, start, mid);
    	merge_sort(array, mid + 1, end);
    
    	if (array.get(mid).compareTo(array.get(mid + 1)) <= 0)
    	    return;
    
    	List<T> arraycopy = new ArrayList<T>();
    	for (int i = start; i <= end; i++)
    	    arraycopy.add(array.get(i));
    
    	int i = start;
    	int j = mid + 1;
    	int index = start;
    	while (i <= mid && j <= end) {
    	    if (arraycopy.get(i - start).compareTo(arraycopy.get(j - start)) > 0) {
    		array.set(index++, arraycopy.get(j++ - start));
    	    } else {
    		array.set(index++, arraycopy.get(i++ - start));
    	    }
    	}
    	while (i <= mid)
    	    array.set(index++, arraycopy.get(i++ - start));
    	while (j <= end)
    	    array.set(index++, arraycopy.get(j++ - start));
    }
}

MergeSort.java

// This is the implementation of mergesort in Java.
public class Main {
    public static void main(String[] args) {
        if (args.length == 0) {
            System.out
                .println("Proper Usage is: java main number1 number2 number3 ...");
            System.exit(0);
        }
        Main main = new Main();
        main.print(args);
        main.merge_sort(args, 0, args.length - 1);
        main.print(args);
    }

    public void print(String[] array) {
        print(array, 0, array.length - 1);
    }

    public void print(String[] array, int start, int end) {
        if (start > end || start < 0 || end > array.length - 1)
            return;
        for (int i = start; i <= end; i++) {
            System.out.print(array[i] + " ");
        }
        System.out.println();
    }

    public void merge_sort(String[] array, int start, int end) {
        print(array, start, end);
        if (end == start)
            return;

        int mid = (start + end) / 2;
        merge_sort(array, start, mid);
        merge_sort(array, mid + 1, end);
    
        if (array[mid].compareTo(array[mid + 1]) <= 0)
            return;
    
        int i = start;
        int j = mid + 1;
        String[] arraycopy = new String[end - start + 1];
        System.arraycopy(array, start, arraycopy, 0, end - start + 1);
        int index = start;
        while (i <= mid && j <= end) {
            if (arraycopy[i - start].compareTo(arraycopy[j - start]) > 0) {
            array[index++] = arraycopy[j++ - start];
            } else {
            array[index++] = arraycopy[i++ - start];
            }
        }
        while (i <= mid)
            array[index++] = arraycopy[i++ - start];
        while (j <= end)
            array[index++] = arraycopy[j++ - start];
    }
}