java中求兩個數組（集合）的交集，並集，差集

對於兩個數組

arr1=[1,3,4,5,8,9]

arr2=[2,3,7,8,9]

求出交集與並集

test.java

 import java.util.ArrayList;
 import java.util.Collections;
 
 
 public class test1 {
     public static void main(String[] args) {
     ArrayList<Integer> tmplist=new ArrayList<Integer>();
     int[] arr1={1,3,4,5,8,9};
     int[] arr2={2,3,7,8,9};
     tmplist=Intersection(arr1,arr2);
     OutPut(tmplist);
     tmplist.clear();
     tmplist=Union(arr1,arr2);
     OutPut(tmplist);
     }
     private static ArrayList<Integer> Intersection(int[] a1,int[] a2){
         ArrayList<Integer> list=new ArrayList<Integer>();
         for(int i=0;i<a1.length;i++)
             for(int j=0;j<a2.length;j++)
                 if(a1[i]==a2[j])
                     list.add(a2[j]);
         return list;
     }
     
     private static ArrayList<Integer> Union(int[] a1,int[] a2){
         ArrayList<Integer> list1=new ArrayList<Integer>();
         ArrayList<Integer> list2=new ArrayList<Integer>();
         for(int i:a1)
             list1.add(i);
         for(int i:a2)
             list2.add(i);
         list1.removeAll(list2);
         list2.addAll(list1);
         return list2;
     }
     
     private static void OutPut(ArrayList<Integer> list){
         Collections.sort(list);
         if(list.size()==0)
             System.out.println("null");
         else
             for(int i:list)
                 System.out.print(i);
         System.out.println("\n");
     }
 }