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}