集合操作的利器:CollectionUtils

使用 CollectionUtils 中四個方法之一執行集合操作.這四種分別是 union(),intersection();disjunction(); subtract();
下列例子就是演示瞭如何使用上述四個方法處理兩個 Collection;
注: 這些方法都是數學的集合算法

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); //並集 Collection<String> union = CollectionUtils.union(a, b); //交集 Collection<String> intersection = CollectionUtils.intersection(a, b); //交集的補集 Collection<String> disjunction = CollectionUtils.disjunction(a, b); //集合相減 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())); } }

輸出如下:
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}