集合操作的利器:CollectionUtils

 使用 CollectionUtils 中四个方法之一执行集合操作.这四种分别是 union(),intersection();disjunction(); subtract();
下列例子就是演示了如何使用上述四个方法处理两个 Collection;
注: 这些方法都是数学的集合算法

 

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

import org.apache.commons.collections.CollectionUtils;
import org.apache.commons.lang.ArrayUtils;

public class CollectionUtilsIntro {
 @SuppressWarnings("unchecked")
 public static void main(String[] args) {
  String[] arrayA = new String[] { "1", "2", "3", "3", "4", "5" };
  String[] arrayB = new String[] { "3", "4", "4", "5", "6", "7" };

  List a = Arrays.asList(arrayA);
  List b = Arrays.asList(arrayB);
  //并集
  Collection union = CollectionUtils.union(a, b);
  //交集
  Collection intersection = CollectionUtils.intersection(a, b);
  //交集的补集
  Collection disjunction = CollectionUtils.disjunction(a, b);
  //集合相减
  Collection subtract = CollectionUtils.subtract(a, b);

  Collections.sort((List) union);
  Collections.sort((List) intersection);
  Collections.sort((List) disjunction);
  Collections.sort((List) subtract);

  System.out.println("A: " + ArrayUtils.toString(a.toArray()));
  System.out.println("B: " + ArrayUtils.toString(b.toArray()));
  System.out.println("--------------------------------------------");
  System.out.println("Union(A, B): " + ArrayUtils.toString(union.toArray()));
  System.out.println("Intersection(A, B): " + ArrayUtils.toString(intersection.toArray()));
  System.out.println("Disjunction(A, B): " + ArrayUtils.toString(disjunction.toArray()));
  System.out.println("Subtract(A, B): " + ArrayUtils.toString(subtract.toArray()));
 }
}