[转]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}

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fengfly.com 补充此工具类一个常用的方法，集合的比较方法，可以实现两个集合间的比较，如List<String>，List<Integer>：

org.apache.commons.collections.CollectionUtils.isEqualCollection(final Collection a, final Collection b)