常用的型別直接把list的值賦值給HashSet就能實現去重，但是當list用來存放物件的時候由於每個物件的存放地址都不同，就算物件的值一模一樣，HashSet也會認為他們是不一樣的物件，所以直接使用之前那種方法去重會失敗。這時要實現去重，重寫需要去重物件的hashcode,和equals方法即可。

Entity

public class Student {
	private String name;
	private String sex;
	private Integer age;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	public Integer getAge() {
		return age;
	}
	public void setAge(Integer age) {
		this.age = age;
	}
    //equals重寫
	@Override
	public boolean equals(Object obj) {
		Student student=(Student)obj;
		return student.getAge().equals(age)&&student.getName().equals(name)&&student.getSex().equals(sex);
	}
    //hashCode重寫
	@Override
	public int hashCode() {
		String in=name+sex+age;
		return in.hashCode();
	}
	@Override
	public String toString() {
		return "Student [name=" + name + ", sex=" + sex + ", age=" + age + "]";
	}
	public Student(String name, String sex, Integer age) {
		this.name = name;
		this.sex = sex;
		this.age = age;
	}

}
 

Test

public static void main(String[] args) {
		List<Student> students=new ArrayList<>();
		students.add(new Student("張飛","男",21));
		students.add(new Student("趙雲","女",21));
		students.add(new Student("于謙","男",21));
		students.add(new Student("張飛","男",21));
		Set<Student> ts = new HashSet<Student>(students);
		students.clear();
		students.addAll(ts);
		students.forEach(student->{
			System.out.println(student.toString());
			
		});


	}
 

輸出結果

Student [name=張飛, sex=男, age=21]
Student [name=于謙, sex=男, age=21]
Student [name=趙雲, sex=女, age=21]