Java中List之间求交集的思路及代码示例

import java.util.*;

public class RetainAllExample {
    public static void main(String[] args) {
        // 示例1：ArrayList 与 HashSet 求交集
        List<String> list = new ArrayList<>(Arrays.asList("A", "B", "C", "D"));
        Set<String> set = new HashSet<>(Arrays.asList("B", "D", "E"));
        
        boolean changed = list.retainAll(set);
        System.out.println("是否改变：" + changed);      // true
        System.out.println("list 交集结果：" + list);    // [B, D]
        
        // 示例2：没有共同元素
        List<Integer> numbers = new ArrayList<>(Arrays.asList(1, 2, 3));
        List<Integer> others = Arrays.asList(4, 5, 6);
        boolean changed2 = numbers.retainAll(others);
        System.out.println("是否改变：" + changed2);     // true
        System.out.println("numbers 结果：" + numbers); // []（空集合）
        
        // 示例3：没有元素被移除
        List<String> colors = new ArrayList<>(Arrays.asList("红", "绿"));
        List<String> keep = Arrays.asList("红", "绿", "蓝");
        boolean changed3 = colors.retainAll(keep);
        System.out.println("是否改变：" + changed3);     // false
        System.out.println("colors 结果：" + colors);    // [红, 绿]（未变）
    }
}