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  1.  
  2. import java.util.ArrayList;
  3. import java.util.List;
  4. import java.util.stream.Collectors;
  5.  
  6. class Mainlove {
  7.  
  8.     private String key;
  9.     private int v1;
  10.     private int v2;
  11.  
  12.     public Mainlove(String key, int v1, int v2) {
  13.         setKey(key);
  14.         setV1(v1);
  15.         setV2(v2);
  16.     }
  17.  
  18.     public String getKey() {
  19.         return key;
  20.     }
  21.  
  22.     public void setKey(String key) {
  23.         this.key = key;
  24.     }
  25.  
  26.     public int getV1() {
  27.         return v1;
  28.     }
  29.  
  30.     public void setV1(int v1) {
  31.         this.v1 = v1;
  32.     }
  33.  
  34.     public int getV2() {
  35.         return v2;
  36.     }
  37.  
  38.     public void setV2(int v2) {
  39.         this.v2 = v2;
  40.     }
  41.  
  42.     public String toString() {
  43.         return String.format("%s %s %s", getKey(), getV1(), getV2());
  44.     }
  45.  
  46.     public static void main(String[] args) {
  47.         List<Mainlove> list = new ArrayList<>();
  48.         list.add(new Mainlove("a", 2, 3));
  49.         list.add(new Mainlove("b", 1, 1));
  50.         list.add(new Mainlove("a", 1, 1));
  51.         list.add(new Mainlove("c", 1, 1));
  52.         list.add(new Mainlove("b", 1, 1));
  53.  
  54.         // https://h...content-available-to-author-only...i.com/article/1507601898720
  55.         // key 进行分组，分组的同时 把 value1 和 value2 求和
  56.         // 最后需要的结果是 [a,3,4] [b,2,2] [c,1,1]
  57.  
  58.  
  59.         List<Mainlove> cml = new ArrayList<>();
  60.  
  61.         list.stream().collect(Collectors.groupingBy(Mainlove::getKey)).forEach((k, v)-> cml.add(new Mainlove(k, v.stream().mapToInt(Mainlove::getV1).sum(), v.stream().mapToInt(Mainlove::getV2).sum())));
  62.  
  63.         cml.forEach(System.out::println);
  64.  
  65.  
  66.     }
  67. }
  68.  
Success #stdin #stdout 0.21s 2841600KB
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stdin
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Standard input is empty
stdout
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a 3 4
b 2 2
c 1 1
https://ideone.com/kWbAG7
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

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