题解 | #合并表记录#

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int i = scanner.nextInt();//首次输入值，确定接下来键值对个数
        HashMap<Integer, String> h = new HashMap<>(i);//新建确定存储个数的无序hashmap
        for (int j = 0; j <i; j++) {
            Integer key = (scanner.nextInt());
            String value = String.valueOf(scanner.nextInt());
            if (h.get(key)==null) {//如果hashmap中键对应值为空，则执行插入操作
                h.put(key, value);
            }else {//如果hashmap中键对应值不为空，则取出旧的值相加新的值
                String s1 = h.get(key);
                int i1 = Integer.parseInt(s1) + Integer.parseInt(value);
                String s2 = String.valueOf(i1);
                h.put(key,s2);//相加后重新放入
            }
        }
        Set<Integer> integers = h.keySet();//返回hashmap中所有 key 组成的 Set 视图
        ArrayList<Integer> integers1 = new ArrayList<>(integers);
        Collections.sort(integers1);//对set视图集合升序重新排序

        LinkedHashMap<Integer,String> linkedHashMap = new LinkedHashMap<Integer, String>(i);
        /*   此处是排序操作   */
        for (int y = 0; y < integers1.size(); y++) {
            linkedHashMap.put(integers1.get(y),h.get(integers1.get(y)));//根据升序排序后的list集合重新向有序的LinkedHashMap内存值
        }
        /*   此处是遍历输出操作   */
        Iterator<Map.Entry<Integer, String>> it = linkedHashMap.entrySet().iterator();
        while (it.hasNext()){
            Map.Entry<Integer, String> next = it.next();
            System.out.println(next.getKey()+" "+next.getValue());
        }
    }
}