Set 求交集、并集、差集

项目中经常遇到需要求两个集合的并集的情况，每次都要度娘，永远记不住????????????，所以干脆自己记下来。

直接上代码：

/**
 * fshows.com
 * Copyright (C) 2013-2019 All Rights Reserved.
 */
package com.fshows.lifecircle.marketcore.common.util;

import com.google.common.collect.Sets;

import java.util.Set;

/**
 * @author liuyuan
 * @version Test.java, v 0.1 2019-12-31 11:27
 */
public class Test {

    public static void main(String[] args) {

        String s1 = "s1";
        String s2 = "s2";
        String s3 = "s3";
        
        Set<String> set1 = Sets.newHashSet();
        set1.add(s1);
        set1.add(s2);
        
        Set<String> set2 = Sets.newHashSet();
        set2.add(s2);
        set2.add(s3);

        // 求交集
        Set intersect = getIntersect(set1, set2);
        // 执行结果：[s2]
        System.out.println(intersect);

        // 求并集
        Set unite = getUnite(set1, set2);
        // 执行结果：[s3, s1, s2]
        System.out.println(unite);

        // 求差集
        Set subtract = getSubtract(set1, set2);
        // 执行结果：[s1]
        System.out.println(subtract);
    }

    /**
     * 求交集
     */
    private static Set getIntersect(Set<?> set1, Set<?> set2) {

        Set<Object> set = Sets.newHashSet();

        set.addAll(set1);
        set.retainAll(set2);

        return set;
    }

    /**
     * 求并集
     */
    private static Set getUnite(Set<?> set1, Set<?> set2) {

        Set<Object> set = Sets.newHashSet();

        set.addAll(set1);
        set.addAll(set2);

        return set;
    }

    /**
     * 求差集 set1 - set2
     */
    private static Set getSubtract(Set<?> set1, Set<?> set2) {

        Set<Object> set = Sets.newHashSet();

        set.addAll(set1);
        set.removeAll(set2);

        return set;
    }
}