Freight trains

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.StringTokenizer;

public class FreightTrains {

    public static void main(String[] args) {
        FastScanner input = new FastScanner(System.in);
        int n = input.nextInt();

        String[] ids = new String[n];

        for (int i = 0; i < n; i++){
            ids[i] = input.nextLine();
        }

        String a;
        String b;
        String ab;
        String ba;

        for (int i = 0; i < n - 1; i++){
            for (int j = 0; j < n - i - 1; j++){

                a = ids[j];
                b = ids[j + 1];
                ab = a+b;
                ba = b+a;

                if (ab.compareTo(ba) > 0) {

                    String temp = ids[j];
                    ids[j] = ids[j + 1];
                    ids[j + 1] = temp;
                }
            }
        }
        System.out.println(java.util.Arrays.toString(ids));

    }

    static class FastScanner { //static class fastScanner
    private BufferedReader reader = null;
    private StringTokenizer tokenizer = null;

    public FastScanner(InputStream in) {
        reader = new BufferedReader(new InputStreamReader(in));
        tokenizer = null;
    }

    public String next() {
        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                tokenizer = new StringTokenizer(reader.readLine());
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken();
    }

    public String nextLine() {
        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                return reader.readLine();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }

        return tokenizer.nextToken("\n");
    }

    public long nextLong() {
        return Long.parseLong(next());
    }

    public int nextInt() {
        return Integer.parseInt(next());
    }

    public double nextDouble() {
    	 return Double.parseDouble(next());
	 }

    public int[] nextIntArray(int n) {
        int[] a = new int[n];
        for (int i = 0; i < n; i++)
            a[i] = nextInt();
        return a;
    }

    public long[] nextLongArray(int n) {
        long[] a = new long[n];
        for (int i = 0; i < n; i++)
            a[i] = nextLong();
        return a;
    }
}
}

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Test 62

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Test 71

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