如何在Java8中添加重复键映射中的值

Question

输入:新字符串[]{“x:-1”,“y:1”,“x:4”,“b:3”,“x:5”}

输出:b:3，y:1

输入:新字符串[]{“z:0”,“a:-1”}

public static String Output(String[] strArr) {
       //strArr = new String[] {"X:-1", "Y:1", "X:-4", "B:3", "X:5"};
        Map<String, Double> kvs =
                Arrays.asList(strArr)
                    .stream()
                    .map(elem -> elem.split(":"))
                    .collect(Collectors.toMap(e -> e[0], e -> Double.parseDouble(e[1])));
        
        kvs.entrySet().forEach(entry->{
            System.out.println(entry.getKey() + " " + entry.getValue());  
         });
        
        return strArr[0];
      }

线程“main”java.lang.IllegalStateException中的异常：重复键-1.0

我怎么才能修好这个？

Answer 1

您应该在第一个流中声明合并策略：

.collect(Collectors.toMap(e -> e[0], e -> Double.parseDouble(e[1]), Double::sum));

然后通过零值过滤映射：

  .filter(s-> s.getValue() != 0)

对于按键使用进行排序：

   .sorted(Map.Entry.comparingByKey())

   String [] strArr = new String[] {"X:-1", "Y:1", "X:-4", "B:3", "X:5"};
    Map<String, Double> kvs =
            Arrays.asList(strArr)
                    .stream()
                    .map(elem -> elem.split(":"))
                    .collect(Collectors.toMap(e -> e[0], e -> Double.parseDouble(e[1]), Double::sum));

    kvs.entrySet().stream()
            .filter(s-> s.getValue() != 0)
            .sorted(Map.Entry.comparingByKey())
            .forEach(entry->{
        System.out.println(entry.getKey() + " " + entry.getValue());w
    });