Java数组/集合去重

你的名字 2022-04-15 03:15 271阅读 0赞

## 一、对数组进行去重： ##

**1、利用java8的stream流**

public class test3 {
    
        public static void main(String[] args) {
            int[] a={1,2,2,3,3,5,4,4,8,6,18};
            System.out.println(Arrays.stream(a).distinct().boxed().collect(Collectors.toList()));
        }
    }

[1, 2, 3, 5, 4, 8, 6, 18]

**如果想要排序的，加上.sorted()即可；**

Arrays.stream(a).distinct().sorted().boxed().collect(Collectors.toList()

**2、HashSet去重**

import java.util.*;
    
    /**
     * @author: Lucifer
     * @create: 2018-11-20 10:42
     * @description:
     **/
    public class test1 {
    
        public static void main(String[] args) {
            int[] a={1,2,2,3,3,5,4,4,8,6,18};
            Set set=new HashSet();
            for (int i = 0; i < a.length; i++) {
                set.add(a[i]);
            }
            if (set.iterator().hasNext()){
                System.out.println(set.toString());
            }
        }
    
    }

**注：输出结果无序：**

[1, 2, 18, 3, 4, 5, 6, 8]

**用TreeSet可以实现既排序又去重,Set set=new TreeSet();**

[1, 2, 3, 4, 5, 6, 8, 18]

###    2、利用集合 ###

import java.util.*;
    
    /**
     * @author: Lucifer
     * @create: 2018-11-20 10:42
     * @description:
     **/
    public class test1 {
    
        public static void main(String[] args) {
            int[] a={1,2,2,3,3,5,4,4,8,6,18};
            List list=new ArrayList();
            List tmplist=new ArrayList();
            for (int i = 0; i < a.length; i++) {
                    list.add(i,a[i]);
            }
            Iterator<Integer> iter = list.iterator();
            while (iter.hasNext()){
                Object t=iter.next();
                if(tmplist.contains(t)){
                    System.out.println(list.toString());
                    iter.remove();
                }else{
                    tmplist.add(t);
                }
            }
            System.out.println("tmplist"+tmplist.toString());
        }
    
    }

** 注：输出结果：**

[1, 2, 2, 3, 3, 5, 4, 4, 8, 6, 18]
    [1, 2, 3, 3, 5, 4, 4, 8, 6, 18]
    [1, 2, 3, 5, 4, 4, 8, 6, 18]
    tmplist[1, 2, 3, 5, 4, 8, 6, 18]

### 二、对集合进行去重 ###

**1、利用java8的stream流**

public class test3 {
    
        public static void main(String[] args) {
            List<Integer> list=new ArrayList<>();
            list.add(1);
            list.add(1);
            list.add(3);
            list.add(4);
            list.add(2);
            list.add(3);
            System.out.println(list.stream().distinct().sorted().collect(Collectors.toList()));
        }
    
    }

** 2、利用hashset去重**

import java.util.ArrayList;
    import java.util.HashSet;
    import java.util.List;
    import java.util.Set;
    
    public class Main {
    
        public static void main(String[] args) {
            List<String> list=new ArrayList<>();
            list.add("a");
            list.add("ab");
            list.add("ca");
            list.add("e");
            list.add("b");
            list.add("ab");
            System.out.println(list);
            Set<String> hashSet = new HashSet<>(list);
            System.out.println(hashSet);
        }
    }

ps：
           Set<String> hashSet = new HashSet<>(list); 等同于Set<String> hashSet = new HashSet<>()；set.addAll(list);