放碼過來

package com.lun.util;import java.util.HashSet;
import java.util.Set;public class SetUtils {public static <T> Set<T> union(Set<T> setA, Set<T> setB) {Set<T> tmp = new HashSet<T>(setA);tmp.addAll(setB);return tmp;}public static <T> Set<T> intersection(Set<T> setA, Set<T> setB) {Set<T> tmp = new HashSet<T>();for (T x : setA)if (setB.contains(x))tmp.add(x);return tmp;}public static <T> Set<T> difference(Set<T> setA, Set<T> setB) {Set<T> tmp = new HashSet<T>(setA);tmp.removeAll(setB);return tmp;}public static <T> Set<T> symDifference(Set<T> setA, Set<T> setB) {Set<T> tmpA;Set<T> tmpB;tmpA = union(setA, setB);tmpB = intersection(setA, setB);return difference(tmpA, tmpB);}public static <T> boolean isSubset(Set<T> setA, Set<T> setB) {return setB.containsAll(setA);}public static <T> boolean isSuperset(Set<T> setA, Set<T> setB) {return setA.containsAll(setB);}public static void main(String args[]) {HashSet<Character> set1 = new HashSet<Character>();HashSet<Character> set2 = new HashSet<Character>();set1.add('A');set1.add('B');set1.add('C');set1.add('D');set2.add('C');set2.add('D');set2.add('E');set2.add('F');System.out.println("set1: " + set1);System.out.println("set2: " + set2);System.out.println("Union: " + union(set1, set2));System.out.println("Intersection: " + intersection(set1, set2));System.out.println("Difference (set1 - set2): " + difference(set1, set2));System.out.println("Difference (set2 - set1): " + difference(set2, set1));System.out.println("Symmetric Difference: " + symDifference(set1, set2));HashSet<Character> set3 = new HashSet<Character>(set1);set3.remove('D');System.out.println("set3: " + set3);System.out.println("Is set1 a subset of set2? " + isSubset(set1, set3));System.out.println("Is set1 a superset of set2? " + isSuperset(set1, set3));System.out.println("Is set3 a subset of set1? " + isSubset(set3, set1));System.out.println("Is set3 a superset of set1? " + isSuperset(set3, set1));}}/* result:set1: [A, B, C, D]
set2: [C, D, E, F]
Union: [A, B, C, D, E, F]
Intersection: [C, D]
Difference (set1 - set2): [A, B]
Difference (set2 - set1): [E, F]
Symmetric Difference: [A, B, E, F]
set3: [A, B, C]
Is set1 a subset of set2? false
Is set1 a superset of set2? true
Is set3 a subset of set1? true
Is set3 a superset of set1? false*/

參考資料

Set operations: union, intersection, difference, symmetric difference, is subset, is superset : Set ? Collections Data Structure ? Java