目录

依赖

这个包下

1.安全检查指定的集合是否为空

2.空 安全检查指定的集合是否为空

3.(String)类型中的集合-并集 union

4.(String)类型中的集合-交集

5.(String)类型中交集的补集

6.(String)类型中差集（扣除）

7.containsAny()方法：判断两个集合是否有交集，如果存在交集则返回true，否则返回false。

8.是否全部包含： containsAll

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依赖

    <dependency><groupId>org.apache.commons</groupId><artifactId>commons-collections4</artifactId><version>4.3</version></dependency>

这个包下

import org.apache.commons.collections4.CollectionUtils;

1.安全检查指定的集合是否为空

@Testpublic void Users12() {List<Users> userList = new ArrayList<>();userList.add(new Users(1, "user1", "password1", 25));userList.add(new Users(2, "user2", "password2", 17));userList.add(new Users(3, "user3", "password3", 19));userList.add(new Users(4, "user4", "password4", 18));userList.add(new Users(5, "user5", "password5", 19));userList.add(new Users(6, "user6", "password6", 20));/*** 空 安全检查指定的集合是否为空*///CollectionUtils.isEmpty(Collection<?> coll)if(CollectionUtils.isEmpty(userList)){System.out.println("集合为空");} else {System.out.println("集合不为空");}}

2.空 安全检查指定的集合是否为空

 @Testpublic void Users12() {List<Users> userList = new ArrayList<>();userList.add(new Users(1, "user1", "password1", 25));userList.add(new Users(2, "user2", "password2", 17));userList.add(new Users(3, "user3", "password3", 19));userList.add(new Users(4, "user4", "password4", 18));userList.add(new Users(5, "user5", "password5", 19));userList.add(new Users(6, "user6", "password6", 20));/*** 空安全检查指定的集合是否为空。*/// CollectionUtils.isNotEmpty(Collection<?> coll)if(CollectionUtils.isNotEmpty(userList)){System.out.println("集合不为空");} else {System.out.println("集合为空");}}

3.(String)类型中的集合-并集 union

 @Testpublic void Users12() {String[] A = new String[] { "A", "2", "3", "4"};String[] B = new String[] { "3", "C", "5", "A" };List<String> listA = Arrays.asList(A);List<String> listB = Arrays.asList(B);//1、并集 union ,就是重复的元素只留一个，本身就是一个的就留System.out.println(CollectionUtils.union(listA, listB));}

4.(String)类型中的集合-交集

@Testpublic void Users18() {String[] A = new String[] { "A", "2", "3", "4"};String[] B = new String[] { "3", "C", "5", "A" };List<String> listA = Arrays.asList(A);List<String> listB = Arrays.asList(B);//交集System.out.println(CollectionUtils.intersection(listA, listB));}

5.(String)类型中交集的补集

 @Testpublic void Users18() {String[] A = new String[] { "A", "2", "3", "4"};String[] B = new String[] { "3", "C", "5", "A" };List<String> listA = Arrays.asList(A);List<String> listB = Arrays.asList(B);//交集的补集System.out.println(CollectionUtils.disjunction(listA, listB));}

6.(String)类型中差集（扣除）

 @Testpublic void Users18() {String[] A = new String[]{"A", "2", "3", "4"};String[] B = new String[]{"3", "C", "5", "A"};List<String> listA = Arrays.asList(A);List<String> listB = Arrays.asList(B);//4、差集（扣除）System.out.println(CollectionUtils.subtract(listA, listB));//输出:[2, 4]System.out.println(CollectionUtils.subtract(listB, listA));//输出:[C, 5]}

7.containsAny()方法：判断两个集合是否有交集，如果存在交集则返回true，否则返回false。

 @Testpublic void Users18() {String[] A = new String[]{"A", "2", "3", "4"};String[] B = new String[]{"3", "C", "5", "A"};List<String> listA = Arrays.asList(A);List<String> listB = Arrays.asList(B);if (CollectionUtils.containsAny(listA,listB)){System.out.println("有相同的数据");}else {System.out.println("没有相同的数据");}}

8.是否全部包含： containsAll

 @Testpublic void Users18() {String[] A = new String[]{"A", "2", "3", "4"};String[] B = new String[]{"3", "C", "5", "A"};List<String> listA = Arrays.asList(A);List<String> listB = Arrays.asList(B);if (CollectionUtils.containsAll(listA,listB)){System.out.println("数据完全相同");}else {System.out.println("数据有不相同的");}System.out.println("-----------------------------------------");String[] A2 = new String[]{"A", "3"};String[] B2 = new String[]{"3", "A"};List<String> listA2 = Arrays.asList(A2);List<String> listB2 = Arrays.asList(B2);if (CollectionUtils.containsAll(listA2,listB2)){System.out.println("数据完全相同");}else {System.out.println("数据有不相同的");}}