物件重複是指物件裡面的變數的值都相等，並不定是地址。list集合儲存的型別是基礎型別還比較好辦，直接把list集合轉換成set集合就會自動去除。

   當set集合儲存的是物件型別時，需要在物件的實體類裡面重寫public boolean equals(Object obj) {} 和 public int hashCode() {} 兩個方法。

  實體類

public class Student {

public String id;
public String name;
public Student() {
}
public Student(String id,String name) {
this.id = id;
this.name = name;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public boolean equals(Object obj) {
Student s=(Student)obj; 
return id.equals(s.id) && name.equals(s.name); 
}
@Override
public int hashCode() {
String in = id + name;
return in.hashCode();
}
}

 

測試類

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class QuSame {
	
	public static void main(String[] args) {
		List<Student> stu = new ArrayList<Student>();
		stu.add(new Student("1","yi"));
		stu.add(new Student("3","san"));
		stu.add(new Student("3","san"));
		stu.add(new Student("2","er"));
		stu.add(new Student("2","er"));
		//set集合儲存的是引用不同地址的物件
		Set<Student> ts = new HashSet<Student>();
		ts.addAll(stu);
		
		for (Student student : ts) {
			System.out.println(student.getId()+"-"+student.getName());
		}
	}
}