集合操作工具类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; 
例子:使用:CollectionUtils union(),intersection();disjunction(); subtract(); 
注: 这些方法都是数学的集合算法 

 import java.util.*;
 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 );

 Collection union = CollectionUtils.union( a, b );  //并集
 Collection intersection = CollectionUtils.intersection( a, b ); //交集
 Collection disjunction = CollectionUtils.disjunction( a, b ); //析取
 Collection subtract = CollectionUtils.subtract( a, b ); //差集

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


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

The previous example performs these four operations on two List objects, a and b, printing the results with ArrayUtils.toString( ): 

结果: 
A: {1,2,2,2,3,3,4,5} 
B: {3,4,4,5,6,7} 
Union: {1,2,2,2,3,3,4,4,5,6,7} 
Intersection: {3,4,5} 
Disjunction: {1,2,2,2,3,4,6,7} 
Subtract: {1,2,2,2,3}