TreeMap集合自定義對象的遍歷排序方式

第一部分：

package day11;
//創建學生類
public class Student{
    //成員變量
    private String name;
    private int age;
    //構造方法
    public Student(){
        super();
    }

    public Student(String name, int age){
        this.name = name;
        this.age = age;
    }
    //成員方法
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

第二部分：

package day11;
import java.util.Comparator;
import java.util.Set;
import java.util.TreeMap;

public class TreDemo2 {
    public static void main(String[] args){
　　　　　　//創建treemap集合對象，並用比較器排序
        TreeMap<Student, String> map = new TreeMap<>(new Comparator<Student>() {
            @Override
            public int compare(Student s1, Student s2) {
                int num = s2.getAge()-s1.getAge();
                int num2 = num==0?s1.getName().compareTo(s2.getName()):num;
                return num2;
            }
        });
　　　　　　　　//添加元素
        Student s1 = new Student("張無忌",50);
        Student s2 = new Student("趙敏",45);
        Student s3 = new Student("金毛獅王",60);
        Student s4 = new Student("周芷若",40);
　　　　　　　　//把元素添加到集合中去
        map.put(s1,"紅樓夢");
        map.put(s2,"西游記");
        map.put(s3,"水滸傳");
        map.put(s4,"捉妖記");

        //獲取鍵的集合
        Set<Student> k = map.keySet();
        //遍歷
        for (Student key: k){
            //根據鍵找值
            String value = map.get(key);
            System.out.println(key.getName()+key.getAge()+"---"+value);
        }
    }
}