Java中计算集合中元素的出现次数统计

import java.util.*;

public class Main {
    public static void main(String[] args) {
        List<String> list = Arrays.asList("apple", "banana", "apple", "orange", "banana", "banana");

        // 使用LinkedHashMap以保持插入顺序
        Map<String, Integer> countMap = new LinkedHashMap<>();

        // 遍历列表并统计每个元素的出现次数
        for (String item : list) {
            countMap.put(item, countMap.getOrDefault(item, 0) + 1);
        }

        // 打印结果
        for (Map.Entry<String, Integer> entry : countMap.entrySet()) {
            System.out.println(entry.getKey() + " : " + entry.getValue());
        }
    }
}

import java.util.*;
import java.util.function.Function;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        List<String> list = Arrays.asList("apple", "banana", "apple", "orange", "banana", "banana");

        // 使用Stream API和lambda表达式来计算元素的出现次数
        Map<String, Long> countMap = list.stream()
                .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

        // 打印结果
        countMap.forEach((item, count) -> System.out.println(item + " : " + count));
    }
}