Merge Sort in Java, Java

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import java.util.Scanner;

class Rextester
{
    private static Scanner sc = new Scanner (System.in);
    
    private static void mergeSort (int[] a, int l, int r)
    {
        if (l < r)
        {
            int mid = l + (r - l) / 2;
            
            mergeSort (a, l, mid);
            mergeSort (a, mid + 1, r);
            
            int i = l, j = mid + 1;
            int k = 0;
            
            int[] merge = new int[r - l + 1];
            while (i <= mid && j <= r)
                merge[k++] = a[i] < a[j] ? a[i++] : a[j++];
            
            while (i <= mid)
                merge[k++] = a[i++];
            
            while (j <= r)
                merge[k++] = a[j++];
            
            for (i = l; i <= r; ++i)
                a[i] = merge[i - l];
        }
    }
    
    public static void main (String[] args)
    {
        int[] a = new int[sc.nextInt()];
        for (int i = 0; i < a.length; ++i)
            a[i] = sc.nextInt();
        
        mergeSort (a, 0, a.length - 1);
        
        for (int i = 0; i < a.length; ++i)
            System.out.print (a[i] + " ");
    }
}

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Compilation time: 1.34 sec, absolute running time: 0.28 sec, cpu time: 0.34 sec, memory peak: 20 Mb, absolute service time: 1,63 sec