Java代码中List如何去重呢？

下文笔者讲述Java代码中对list去重的6种方法分享，如下所示:

List双重循环去重

遍历集合，将集合种不存在的数据放入另一个集合中
当存在时，则不放入集合中

String[] array = {"a","b","c","c","d","e","e","e","a"};  
List<String> result = new ArrayList<>();  
boolean flag;  
for(int i=0;i<array.length;i++){  
    flag = false;  
    for(int j=0;j<result.size();j++){  
        if(array[i].equals(result.get(j))){  
            flag = true;  
            break;  
        }  
    }  
    if(!flag){  
        result.add(array[i]);  
    }  
} 
String[] arrayResult = (String[]) result.toArray(new String[result.size()]);  
System.out.println(Arrays.toString(arrayResult));  

使用indexOf方法进行判断结果集中是否存在了数组元素去重

String[] array = {"a","b","c","c","d","e","e","e","a"};  
List<String> list = new ArrayList<>();  
list.add(array[0]);  
for(int i=1;i<array.length;i++){  
    if(list.toString().indexOf(array[i]) == -1){  
            list.add(array[i]);  
    }  
}  
String[] arrayResult = (String[]) list.toArray(new String[list.size()]);  
System.out.println(Arrays.toString(arrayResult));  

嵌套循环去重

String[] array = {"a","b","c","c","d","e","e","e","a"};  
List<String> list = new ArrayList<>();  
for(int i=0;i<array.length;i++){  
    for(int j=i+1;j<array.length;j++){  
        if(array[i] == array[j]){  
            j = ++i;  
        }  
    }  
    list.add(array[i]);  
}  
String[] arrayResult = (String[]) list.toArray(new String[list.size()]);  
System.out.println(Arrays.toString(arrayResult));

sort排序，相邻比较去重

String[] array = {"a","b","c","c","d","e","e","e","a"};  
Arrays.sort(array);  
List<String> list = new ArrayList<>();  
list.add(array[0]);  
for(int i=1;i<array.length;i++){  
    if(!array[i].equals(list.get(list.size()-1))){  
 list.add(array[i]);  
    }  
}
String[] arrayResult = (String[]) list.toArray(new String[list.size()]);  

set方法无序排列去重

set 集合自身无法插入重复的数据，借助这个特性，则实现去重的操作

String[] array = {"a","b","c","c","d","e","e","e","a"};  
Set<String> set = new HashSet<>();  
for(int i=0;i<array.length;i++){  
    set.add(array[i]);  
}  
String[] arrayResult = (String[]) set.toArray(new String[set.size()]);  
System.out.println(Arrays.toString(arrayResult));  

使用Iterator遍历,remove方法移除去重

public void testList() {  
 List<Integer> list=new ArrayList<Integer>();  
 list.add(7);  
 list.add(8);  
 list.add(2);  
 list.add(7);  
 list.add(8);  
 list.add(8);  
 list.add(100);  
 List<Integer> listTemp= new ArrayList<Integer>();  
 Iterator<Integer> it=list.iterator();  
 while(it.hasNext()){  
  int a=it.next();  
  if(listTemp.contains(a)){  
   it.remove();  
  }  
  else{  
   listTemp.add(a);  
  }  
 }  
 for(Integer i:list){  
  System.out.println(i);  
 }  
}