list简单去重代码

ゞ浴缸里的玫瑰 2022-10-05 00:54 106阅读 0赞

### 文章目录 ###

*  记录一下集合去重的几种方法
 *   *  stream去重，推荐，使用java8的stream api的distinct方法去重
     *  LinkedHashSet去重，推荐，返回的数据顺序不变。可以使用hashset，但是不保证顺序。可以根据要求来。
     *  Collection的的contains方法进行判断。可以使用list（有序）也可以使用set（无序）。
     *  双重for删除，不方便看。
     *  main代码：

# 记录一下集合去重的几种方法 #

## stream去重，推荐，使用java8的stream api的distinct方法去重 ##

public static void main(String[] args) { 
            ArrayList<String> list = new ArrayList<>(Arrays.asList("a","a","b","b","b","c"));
            System.out.println(JSONObject.toJSONString(list));
            repeatRemovetest1(list);
        }
    
    
        public static void repeatRemovetest1(List<String> list) { 
            List<String> listWithoutDuplicates = list.stream().distinct().collect(Collectors.toList());
            System.out.println(listWithoutDuplicates);
        }

## LinkedHashSet去重，推荐，返回的数据顺序不变。可以使用hashset，但是不保证顺序。可以根据要求来。 ##

public static void main(String[] args) { 
            ArrayList<String> list = new ArrayList<>(Arrays.asList("a","a","b","b","b","c"));
            System.out.println(JSONObject.toJSONString(list));
            repeatRemovetest2(list);
        }
    
      public static void repeatRemovetest2(List<String> list) { 
            LinkedHashSet<String> linkSet = new LinkedHashSet<>(list);
            ArrayList<String> listWithoutDuplicates = new ArrayList<>(linkSet);
            System.out.println(listWithoutDuplicates);
        }

## Collection的的contains方法进行判断。可以使用list（有序）也可以使用set（无序）。 ##

public static void main(String[] args) { 
            ArrayList<String> list = new ArrayList<>(Arrays.asList("a","a","b","b","b","c"));
            System.out.println(JSONObject.toJSONString(list));
            repeatRemovetest3(list);
        }
    
        public static void repeatRemovetest3(List<String> list) { 
            HashSet<Object> sets = new HashSet<>();
            ArrayList<String> temList = new ArrayList<>(list.size());
            for (String s : list) { 
                if (!temList.contains(s)) { 
                    temList.add(s);
                }
            }
            System.out.println(temList);
        }

## 双重for删除，不方便看。 ##

public static void main(String[] args) { 
            ArrayList<String> list = new ArrayList<>(Arrays.asList("a", "a", "b", "b", "b", "c"));
            System.out.println(JSONObject.toJSONString(list));
            repeatRemovetest4(list);
        }
        
     public static void repeatRemovetest4(List<String> list) { 
            for (int i = 0; i < list.size(); i++) { 
                for (int j = 0; j < list.size(); j++) { 
                    if (i != j && list.get(i) == list.get(j)) { 
                        list.remove(list.get(j));
                    }
                }
            }
            System.out.println(list);
        }

## main代码： ##

import com.alibaba.fastjson.JSONObject;
    
    import java.util.*;
    import java.util.stream.Collectors;
    
    public class RepeatRemoveTest { 
    
        public static void main(String[] args) { 
            ArrayList<String> list = new ArrayList<>(Arrays.asList("a", "a", "b", "b", "b", "c"));
            System.out.println(JSONObject.toJSONString(list));
            repeatRemovetest4(list);
        }
    
    
        public static void repeatRemovetest1(List<String> list) { 
            List<String> listWithoutDuplicates = list.stream().distinct().collect(Collectors.toList());
            System.out.println(listWithoutDuplicates);
        }
    
        public static void repeatRemovetest2(List<String> list) { 
            LinkedHashSet<String> linkSet = new LinkedHashSet<>(list);
            ArrayList<String> listWithoutDuplicates = new ArrayList<>(linkSet);
            System.out.println(listWithoutDuplicates);
        }
    
        public static void repeatRemovetest3(List<String> list) { 
            HashSet<Object> objects = new HashSet<>();
            ArrayList<String> temList = new ArrayList<>(list.size());
            for (String s : list) { 
                if (!temList.contains(s)) { 
                    temList.add(s);
                }
            }
            System.out.println(temList);
        }
    
        public static void repeatRemovetest4(List<String> list) { 
            for (int i = 0; i < list.size(); i++) { 
                for (int j = 0; j < list.size(); j++) { 
                    if (i != j && list.get(i) == list.get(j)) { 
                        list.remove(list.get(j));
                    }
                }
            }
            System.out.println(list);
        }
    
    }