集合工具类 org.apache.commons.collections.CollectionUtils

import org.apache.commons.collections.CollectionUtils;

import java.util.ArrayList;
import java.util.List;

public class CollectionUtilsTest {

 public static void main(String[] args) {
    List a = new ArrayList();
    List b = null;
    List c = new ArrayList();
    c.add(5);
    c.add(6);
    //判断集合是否为空
    System.out.println(CollectionUtils.isEmpty(a));   //true
    System.out.println(CollectionUtils.isEmpty(b));   //true
    System.out.println(CollectionUtils.isEmpty(c));   //false

    //判断集合是否不为空
    System.out.println(CollectionUtils.isNotEmpty(a));   //false
    System.out.println(CollectionUtils.isNotEmpty(b));   //false
    System.out.println(CollectionUtils.isNotEmpty(c));   //true

    //两个集合间的操作
    List e = new ArrayList();
    e.add(2);
    e.add(1);
    List f = new ArrayList();
    f.add(1);
    f.add(2);
    List g = new ArrayList();
    g.add(12);
    //比较两集合值
    System.out.println(CollectionUtils.isEqualCollection(e,f));   //true
    System.out.println(CollectionUtils.isEqualCollection(f,g));   //false

    List h = new ArrayList();
    h.add(1);
    h.add(2);
    h.add(3);;
    List i = new ArrayList();
    i.add(3);
    i.add(3);
    i.add(4);
    i.add(5);
    //并集
    System.out.println(CollectionUtils.union(i,h));  //[1, 2, 3, 3, 4, 5]
    //交集
    System.out.println(CollectionUtils.intersection(i,h)); //[3]
    //交集的补集
    System.out.println(CollectionUtils.disjunction(i,h)); //[1, 2, 3, 4, 5]
    //e与h的差
    System.out.println(CollectionUtils.subtract(h,i)); //[1, 2]
    System.out.println(CollectionUtils.subtract(i,h)); //[3, 4, 5]

}

}