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>();
 8int[] arr1={1,3,4,5,8,9};
 9int[] 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    }
16privatestatic ArrayList<Integer> Intersection(int[] a1,int[] a2){
17         ArrayList<Integer> list=new ArrayList<Integer>();
18for(int i=0;i<a1.length;i++)
19for(int j=0;j<a2.length;j++)
20if(a1[i]==a2[j])
21                    list.add(a2[j]);
22return list;
23    }
2425privatestatic ArrayList<Integer> Union(int[] a1,int[] a2){
26         ArrayList<Integer> list1=new ArrayList<Integer>();
27         ArrayList<Integer> list2=new ArrayList<Integer>();
28for(int i:a1)
29            list1.add(i);
30for(int i:a2)
31            list2.add(i);
32        list1.removeAll(list2);
33        list2.addAll(list1);
34return list2;
35    }
3637privatestaticvoid OutPut(ArrayList<Integer> list){
38        Collections.sort(list);
39if(list.size()==0)
40             System.out.println("null");
41else42for(int i:list)
43                System.out.print(i);
44         System.out.println("\n");
45    }
46 }