java CollectionUtils 包

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}