백준 10814번(Java)

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

public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		
		int N = Integer.parseInt(br.readLine());
		String[][] arr = new String[N][2];
		
		for(int i=0; i<N; i++) {
			StringTokenizer st = new StringTokenizer(br.readLine()," ");
			arr[i][0] = st.nextToken();
			arr[i][1] = st.nextToken();			
		}
		
		Arrays.sort(arr, new Comparator<String[]>() {
			
			public int compare(String[] s1, String[] s2) {
				return Integer.parseInt(s1[0]) - Integer.parseInt(s2[0]);
			}
		});
		
		StringBuilder sb = new StringBuilder();
		
		for(int i=0; i<N; i++) {
			sb.append(arr[i][0]).append(' ').append(arr[i][1]).append('\n');
		}
		
		System.out.println(sb);
	}
}