[转帖]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<String> a = Arrays.asList(arrayA);   
  List<String> b = Arrays.asList(arrayB);   
  //并集   
  Collection<String> union = CollectionUtils.union(a, b);   
  //交集   
  Collection<String> intersection = CollectionUtils.intersection(a, b);   
  //交集的补集   
  Collection<String> disjunction = CollectionUtils.disjunction(a, b);   
  //集合相减   
  Collection<String> subtract = CollectionUtils.subtract(a, b);   
  
  Collections.sort((List<String>) union);   
  Collections.sort((List<String>) intersection);   
  Collections.sort((List<String>) disjunction);   
  Collections.sort((List<String>) 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()));   
 }   
}  

输出如下:
A: {1,2,3,3,4,5}
B: {3,4,4,5,6,7}
--------------------------------------------
Union(A, B): {1,2,3,3,4,4,5,6,7}
Intersection(A, B): {3,4,5}
Disjunction(A, B): {1,2,3,4,6,7}
Subtract(A, B): {1,2,3}