java - 如何获得数组中五个最少重复的元素

Question

如果我有以下字符串数组。

String inStrings[] = {"A", "B", "C", "D", "E", "F", "G", "H", "A", "B", "C", "D", "E", "A", "B", "C", "D", "A", "B"};

然后这个数组被传递给一个方法，我不确定如何继续。

    static void getColdSearch(String[] inArray){



}

这个方法应该做的是获取数组，获取重复次数最少的字符串，然后在输出中打印出重复次数最少的五个字符串。重复的字符串不必彼此相邻，如果字符串少于五个，那么所有字符串都应该是输出的一部分。例如。如果 arraylist 看起来像上面的例子，输出应该是这样的。

F //(Occurs once)
G //(Occurs once)
H //(Occurs once)
E //(Occurs twice)
D //(if two different elements repeat the same number of times a random one of them should be printed)

我该怎么做？

Answer 1

尝试 java 8 特性

import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collectors;

public class GroupingDemo {

    public static void getColdSearch(String[] inArray) {
        Map<String, Long> groupingByLetter = Arrays.stream(inArray)
            .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

        List<String> result = groupingByLetter.entrySet().stream()
            .sorted(Map.Entry.comparingByValue())
            .limit(5)
            .map(Map.Entry::getKey)
            .collect(Collectors.toList());

        System.out.println(result);
    }

    public static void main(String[] args) {
        String inStrings[] = {"A", "B", "C", "D", "E", "F", "G", "H", "A", "B", "C", "D", "E", "A", "B", "C", "D", "A", "B"};
        getColdSearch(inStrings);
    }
}