使用LinkedHashSet删除arraylist中的重复数据(有序)
List words= Arrays.asList("a","b","b","c","c","d");
HashSet set=new LinkedHashSet<>(words);
for(String word:set){
System.out.println(word);
}
使用HashSet去重(无序)
//去掉List集合中重复的元素
List words= Arrays.asList("a","b","b","c","c","d");
//方案一：
for(String word:words){
set.add(word);
}
for(String word:set){
System.out.println(word);
}
使用java8新特性stream进行List去重
List words= Arrays.asList("a","b","b","c","c","d");
words.stream().distinct().collect(Collectors.toList()).forEach(System.out::println);
利用List的contains方法循环遍历
List list= new ArrayList<>();
for (String s:words) {
if (!list.contains(s)) {
list.add(s);
}
}
注：当数据元素是实体类时，需要额外重写equals()和hashCode()方法。
例如：
以学号为依据判断重复
public class Student {
String id;
String name;
int age;
public Student(String id, String name, int age) {
this.id = id;
this.name = name;
this.age = age;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Student student = (Student) o;
return Objects.equals(id, student.id);
}
@Override
public int hashCode() {
return id != null ? id.hashCode() : 0;
}
@Override
public String toString() {
return "Student{" +
"id='" + id + '\'' +
", name='" + name + '\'' +
", age=" + age +
'}';
}
}
