题解 | #合并表记录#

import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
import java.util.stream.Collectors;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {

    private static Map<Integer, Integer> map = new HashMap<>();
    public static void main(String[] args) {

        int count = -1;
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case

            int a = in.nextInt();
            if(count == -1){
                count = a;
            } else{
                int b = in.nextInt();
                init(a,b);
            }
        }
        result();
    }

    private static void result(){

        List<Integer> keys = map.keySet().stream().collect(Collectors.toList());
        keys.sort(Comparator.naturalOrder());
        
        keys.forEach(i -> {
            System.out.println(i+" "+map.get(i));
        });
    }

    private static void init(int k,int v){
        map.put(k, map.getOrDefault(k,0)+v);
        
    }
}