java中求两个数组（集合）的交集，并集，差集

 1 import java.util.ArrayList;
 2 import java.util.Collections;
 3 
 4 
 5 public class test1 {
 6     public static void main(String[] args) {
 7     ArrayList<Integer> tmplist=new ArrayList<Integer>();
 8     int[] arr1={1,3,4,5,8,9};
 9     int[] arr2={2,3,7,8,9};
10     tmplist=Intersection(arr1,arr2);
11     OutPut(tmplist);
12     tmplist.clear();
13     tmplist=Union(arr1,arr2);
14     OutPut(tmplist);
15     }
16     private static ArrayList<Integer> Intersection(int[] a1,int[] a2){
17         ArrayList<Integer> list=new ArrayList<Integer>();
18         for(int i=0;i<a1.length;i++)
19             for(int j=0;j<a2.length;j++)
20                 if(a1[i]==a2[j])
21                     list.add(a2[j]);
22         return list;
23     }
24     
25     private static ArrayList<Integer> Union(int[] a1,int[] a2){
26         ArrayList<Integer> list1=new ArrayList<Integer>();
27         ArrayList<Integer> list2=new ArrayList<Integer>();
28         for(int i:a1)
29             list1.add(i);
30         for(int i:a2)
31             list2.add(i);
32         list1.removeAll(list2);
33         list2.addAll(list1);
34         return list2;
35     }
36     
37     private static void OutPut(ArrayList<Integer> list){
38         Collections.sort(list);
39         if(list.size()==0)
40             System.out.println("null");
41         else
42             for(int i:list)
43                 System.out.print(i);
44         System.out.println("\n");
45     }
46 }