JAVA——两个List集合求交集、并集和差集（去重）

https://juejin.cn/post/6899000526613151752

@Test
public void splitGetPositionOne2() throws Exception {
    List<String> stringList = new ArrayList<>();
    stringList.add("a");
    stringList.add("b");
    stringList.add("c");
    stringList.add("i");
    stringList.add("j");
    stringList.add("a");

    //一、求交集
    //方法1：直接通过retainAll直接过滤
    List<String> stringList1 =  new ArrayList<>(Arrays.asList("a,b,c,d,e,f,g,h".split(",")));
    stringList1.retainAll(stringList);
    System.out.println("交集1: " + stringList1);

    //方法2：通过过滤掉存在于stringList的数据
    List<String> stringList1_2 = new ArrayList<>(Arrays.asList("a,b,c,d,e,f,g,h".split(",")));
    List<String> strings = stringList1_2.stream()
            .filter(item -> stringList.contains(item))
            .collect(Collectors.toList());
    System.out.println("交集2：" + strings);

    //二、并集
    //有重并集
    List<String> stringList2 =  new ArrayList<>(Arrays.asList("a,b,c,d,e,f,g,h".split(",")));
    stringList2.addAll(stringList);
    System.out.println("并集: " + stringList2);

    //无重并集
    List<String> stringList2_2 =  new ArrayList<>(Arrays.asList("a,b,c,d,e,f,g,h".split(",")));
    List<String> stringList_1 =  new ArrayList<>(Arrays.asList("a,b,c,i,j,a".split(",")));
    stringList2_2.removeAll(stringList_1);
    stringList_1.addAll(stringList2_2);

    System.out.println("无重并集: " + stringList_1);

    //三、求差集
    //方法1：直接使用removeAll()方法
    List<String> stringList3 =  new ArrayList<>(Arrays.asList("a,b,c,d,e,f,g,h".split(",")));
    stringList3.removeAll(stringList);
    System.out.println("差集1: " + stringList3);

    //方法2：通过过滤掉不存在于stringList的数据，然后和本数组进行交集处理
    List<String> stringList3_2 = new ArrayList<>(Arrays.asList("a,b,c,d,e,f,g,h".split(",")));
    stringList3_2.retainAll(stringList3_2.stream()
            .filter(item -> !stringList.contains(item))
            .collect(Collectors.toList()));
    System.out.println("差集2：" + stringList3_2);

    



}

 

public static void main(String[] args) { List<String> stringList = new ArrayList<>(); stringList.add("a"); stringList.add("b"); stringList.add("c"); stringList.add("i"); stringList.add("j"); stringList.add("a"); //一、求交集 //方法1：直接通过retainAll直接过滤 List<String> stringList1 = new ArrayList<>(Arrays.asList("a,b,c,d,e,f,g,h".split(","))); stringList1.retainAll(stringList); System.out.println("交集1: " + stringList1); //方法2：通过过滤掉存在于stringList的数据 List<String> stringList1_2 = new ArrayList<>(Arrays.asList("a,b,c,d,e,f,g,h".split(","))); List<String> strings = stringList1_2.stream() .filter(item -> stringList.contains(item)) .collect(toList()); System.out.println("交集2：" + strings); //二、并集 //有重并集 List<String> stringList2 = new ArrayList<>(Arrays.asList("a,b,c,d,e,f,g,h".split(","))); stringList2.addAll(stringList); System.out.println("并集: " + stringList2); //无重并集 List<String> stringList2_2 = new ArrayList<>(Arrays.asList("a,b,c,d,e,f,g,h".split(","))); List<String> stringList_1 = new ArrayList<>(Arrays.asList("a,b,c,i,j,a".split(","))); stringList2_2.removeAll(stringList_1); stringList_1.addAll(stringList2_2); System.out.println("无重并集: " + stringList_1); //三、求差集 //方法1：直接使用removeAll()方法 List<String> stringList3 = new ArrayList<>(Arrays.asList("a,b,c,d,e,f,g,h".split(","))); stringList3.removeAll(stringList); System.out.println("差集1: " + stringList3); //方法2：通过过滤掉不存在于stringList的数据，然后和本数组进行交集处理 List<String> stringList3_2 = new ArrayList<>(Arrays.asList("a,b,c,d,e,f,g,h".split(","))); stringList3_2.retainAll(stringList3_2.stream() .filter(item -> !stringList.contains(item)) .collect(toList())); System.out.println("差集2：" + stringList3_2); SpringApplication.run(DemoApplication.class, args); }

作者：Andya
链接：https://juejin.cn/post/6899000526613151752
来源：稀土掘金
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