求交集、並集和差集

 

import java.util.*;
class Test
{
  public static void main(String args[])
  {
    String num1[]={"Tom","Jim","John","Lucy","Jane","Lizz"};
    String num2[]={"Katie","John","Lucy","Machelle","George"};
    HashSet<String> A=new HashSet<String>(Arrays.asList(num1));       
    HashSet<String> B=new HashSet<String>(Arrays.asList(num2));      
    HashSet<String> Aa=new HashSet<String>(A);
    HashSet<String> Bb=new HashSet<String>(B);
   /*
    HashSet<String> Aa=new HashSet<String>(A);
    HashSet<String> Bb=new HashSet<String>(B);
    可寫成
    HashSet<String> Aa=new HashSet<String>();
    HashSet<String> Bb=new HashSet<String>();
    Aa.addAll(A);
    Bb.addAll(B);
    */
   System.out.println("交集結果爲 ");
    if(A.retainAll(B)==true)
    {
       System.out.println(A);
    }
     A=Aa;
     B=Bb;
    System.out.println("並集結果爲 ");
    if(A.addAll(B)==true)
    {
       System.out.println(A);
    }
     A=Aa;
     B=Bb;
     System.out.println("差集結果爲 ");
    if(A.removeAll(B)==true)
    {
       System.out.println(A);
    }
    
  }
}