geeksforgeeks@ Largest Number formed from an Array

http://www.practice.geeksforgeeks.org/problem-page.php?pid=380

Largest Number formed from an Array

Given a list of non negative integers, arrange them in such a manner that they form the largest number possible.

The result is going to be very large, hence return the result in the form of a string.

Input:

The first line of input consists number of the test cases. The description of T test cases is as follows:

The first line of each test case contains the size of the array, and the second line has the elements of the array.

Output:

In each separate line print the largest number formed by arranging the elements of the array in the form of a string.

Constraints:

1 ≤ T ≤ 70
1 ≤ N ≤ 100
0 ≤ A[i] ≤ 1000

Example:

Input:

2
5
3 30 34 5 9
4
54 546 548 60

Output:

9534330
6054854654

import java.util.*;
import java.lang.*;
import java.io.*;

class Entry {
    public String str;
    public Entry(String s) {
        super();
        this.str = s;
    }
}

class cmp implements Comparator<Entry> {

    public int compare(Entry e1, Entry e2) {
        String s1 = e1.str;
        String s2 = e2.str;

        StringBuffer combo1 = new StringBuffer();
        StringBuffer combo2 = new StringBuffer();

        combo1.append(s1); combo1.append(s2);
        combo2.append(s2); combo2.append(s1);

        return (combo2.toString()).compareTo(combo1.toString());
    }
}

class GFG {

    public static String func(int[] arr) {

        int n = arr.length;
        ArrayList<Entry> ls = new ArrayList<Entry> ();
        for(int i=0; i<n; ++i) {
            Entry entry = new Entry(Integer.toString(arr[i]));
            ls.add(entry);
        }

        Collections.sort(ls, new cmp());
        StringBuffer sb = new StringBuffer();
        for(Entry entry: ls) {
            sb.append(entry.str);
        }
        return sb.toString();
    }

    public static void main (String[] args) {
        Scanner in = new Scanner(System.in);
        int times = in.nextInt();

        for(int i=0; i<times; ++i) {
            int n = in.nextInt();
            int[] arr = new int[n];
            for(int j=0; j<n; ++j) {
                arr[j] = in.nextInt();
            }
            System.out.println(func(arr));
        }
    }
}