MergeSort.java

import java.util.*;
public class MergeSort {
    public static void main(String[] args){
        int[] arr = {5, 4, 3, 8, 0, 9, 2};
        arr = mergeSort(arr);
        System.out.println(Arrays.toString(arr));
    }

    static int[] mergeSort(int[] arr){
        if(arr.length == 1){
            return arr;
        }

        int mid = arr.length/2;

        int[] left = mergeSort(Arrays.copyOfRange(arr, 0, mid));
        int[] right = mergeSort(Arrays.copyOfRange(arr, mid, arr.length));

        return merge(left, right);

    }

    private static int[] merge(int[] first, int[] second){
        int[] mix = new int[first.length + second.length];

        int i = 0;
        int j = 0;
        int k = 0;

        while(i < first.length && j < second.length){
            if(first[i] < second[j]){
                mix[k] = first[i];
                i++;
                k++;
            }else{
                mix[k] = second[j];
                j++;
                k++;
            }
        }

        while(i < first.length){
            mix[k] = first[i];
            i++;
            k++;
        }

        while(j < second.length){
            mix[k] = second[j];
            j++;
            k++;
        }

        return mix;
    }
}