java list 交集 並集 差集 去重複並集

集合

package com;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class Test {

 public static void main(String[] args) {
  List list1 =new ArrayList();
  list1.add("1111");
  list1.add("2222");
  list1.add("3333");

  List list2 =new ArrayList();
  list2.add("3333");
  list2.add("4444");
  list2.add("5555");

  //並集
  //list1.addAll(list2);
  //交集
  //list1.retainAll(list2);
  //差集
  //list1.removeAll(list2);
  //無重複並集
    list2.removeAll(list1);
    list1.addAll(list2);

  Iterator<String> it=list1.iterator();
  while (it.hasNext()) {
   System.out.println(it.next());

  }

  //System.out.println("-----------------------------------\n");
  //printStr(list1);

 }

 public static void printStr(List list1){
  for (int i = 0; i < list1.size(); i++) {
   System.out.println(list1.get(i));
  }
 }
}

數組

package com.wish.datastrustudy; 
import java.util.HashSet;   
import java.util.LinkedList;   
import java.util.List;
import java.util.Set;   
public class StringArray {   
    public static void main(String[] args) {   
        //測試union   
        String[] arr1 = {"abc", "df", "abc","dd","bdfe"};   
        String[] arr2 = {"abc", "cc", "df", "d", "abc"};   
        String[] result_union = union(arr1, arr2);   
        System.out.println("求並集的結果如下：");   
        for (String str : result_union) {   
            System.out.println(str);   
        }   

        //測試insect   
        String[] result_insect = intersect(arr1, arr2);   
        System.out.println("求交集的結果如下：");   
        for (String str : result_insect) {   
            System.out.println(str);   
        }   
         //測試 substract
        String[] result_minus = substract(arr1, arr2);   
        System.out.println("求差集的結果如下：");   
        for (String str : result_minus) {   
            System.out.println(str);   
        }   
    }   

    //並集（set唯一性）
    public static String[] union (String[] arr1, String[] arr2){
        Set<String> hs = new HashSet<String>();
        for(String str:arr1){
            hs.add(str);
        }
        for(String str:arr2){
            hs.add(str);
        }
        String[] result={};
        return hs.toArray(result);
    }

    //交集(注意結果集中若使用LinkedList添加，則需要判斷是否包含該元素，否則其中會包含重複的元素)
    public static String[] intersect(String[] arr1, String[] arr2){
        List<String> l = new LinkedList<String>();
        Set<String> common = new HashSet<String>();                  
        for(String str:arr1){
            if(!l.contains(str)){
                l.add(str);
            }
        }
        for(String str:arr2){
            if(l.contains(str)){
                common.add(str);
            }
        }
        String[] result={};
        return common.toArray(result);
    }
    //求兩個數組的差集   
    public static String[] substract(String[] arr1, String[] arr2) {   
        LinkedList<String> list = new LinkedList<String>();   
        for (String str : arr1) {   
            if(!list.contains(str)) {   
                list.add(str);   
            }   
        }   
        for (String str : arr2) {   
            if (list.contains(str)) {   
                list.remove(str);   
            } 
        }   
        String[] result = {};   
        return list.toArray(result);   
    }   
}