如何将Map的相似值汇总在一起

Question

我在下面有这个输入，它显示了一个人在什么年龄有什么分数。 这存储在像这样Map<Person, Information> 的HashMap 中，Person 类只有double: getScore()，它返回分数，而类Information 有int:getAge()，它返回年龄。类中没有属性名。

   {Person has at Age: 12 (Score: 50)
=alex,
 Person has at Age: 16 (Score: 50)
=miki, 
Person has at Age: 5 (Score: 100)
=shi, 
Person has at Age: 4 (Score: 50)
=rafi, 
Person has at Age: 1 (Score: 50). (Score: 50)
=sharbel, 
Person has at Age: 5 (Score: 0). (Score: 0)
=thomas, 
Person has at Age: 14 (Score: 60). (Score: 60)
=thomy, 
Person has at Age: 14 (Score: 50). (Score: 50)
=angelos,
 Person has at Age: 11 (Score: 50). (Score: 50)
=musti, 
Person has at Age: 11 (Score: 100). (Score: 100)
=aloo,
 Person has at Age: 2 (Score: 50). (Score: 50)
=evi}

我需要的是，将年龄相同且得分最高的用户分组。预期的输出应该是这样的：

{Person has at Age: 12 (Score: 50)
=alex,
 Person has at Age: 16 (Score: 50)
=miki, 
Person has at Age: 5 (Score: 100)
=[shi,thomas], // those are together
Person has at Age: 4 (Score: 50)
=rafi, 
Person has at Age: 1 (Score: 50)
=sharbel, 

Person has at Age: 14 (Score: 60).
=[thomy , angelos], // those are together and we consider the biggest score 60

 Person has at Age: 11 (Score: 100)
=[musti, aloo],  // those are together and we consider the biggest score 100
 Person has at Age: 2 (Score: 50)
=evi}

所以请注意[thomy, angelos] 和[musti, aloo] 在一起，这是因为他们的年龄相同，我们认为他们之间的得分最大。

我尝试了许多不同的方法，但都没有成功，因此我没有尝试任何实现。

Answer 1

你可以像这样使用流：

Map<Person, List<String>> result = origin.entrySet().stream()
        .collect(Collectors.groupingBy(e -> e.getKey().getAge())).entrySet().stream()
        .collect(Collectors.toMap(
                e -> e.getValue().stream()
                        .map(Map.Entry::getKey)
                        .max(Comparator.comparing(Person::getScore))
                        .get(),
                e -> e.getValue().stream()
                        .map(Map.Entry::getValue)
                        .collect(Collectors.toList()))
        );

但我建议使用另一种方式，使用简单的类而不是复杂的 Map。

输出

Person(score=50.0, age=1) - [sharbel]
Person(score=100.0, age=11) - [aloo, musti]
Person(score=50.0, age=12) - [alex]
Person(score=60.0, age=14) - [thomy, angelos]
Person(score=50.0, age=2) - [evi]
Person(score=100.0, age=5) - [shi, thomas]
Person(score=50.0, age=4) - [rafi]
Person(score=50.0, age=16) - [miki]