TreeSet的用法

package com.shrimpking.t13;

import java.util.Comparator;

/**
 * Created by IntelliJ IDEA.
 *
 * @Author : Shrimpking
 * @create 2024/9/10 15:28
 */
public class Student implements Comparable<Student>
{

    private int no;
    private String name;

    public Student(int no, String name)
    {
        this.no = no;
        this.name = name;
    }

    @Override
    public String toString()
    {
        return "Student{" + "no=" + no + ", name='" + name + '\'' + '}';
    }

    @Override
    public int compareTo(Student stu)
    {
        //升序排列
        return this.no > stu.no ? 1 : ( this.no < stu.no ? -1 : 0);
    }

    public static class StudentComparator implements Comparator<Student>{

        @Override
        public int compare(Student o1, Student o2)
        {
            //降序排列
            return o1.no > o2.no ? -1 : ( o1.no < o2.no ? 1 : 0);
        }
    }
}

package com.shrimpking.t13;

import javax.print.attribute.standard.JobKOctetsSupported;
import java.util.Arrays;
import java.util.TreeSet;

/**
 * Created by IntelliJ IDEA.
 *
 * @Author : Shrimpking
 * @create 2024/9/10 15:33
 */
public class UseTreeSet
{
    public static void main(String[] args)
    {
        TreeSet<Integer> ts = new TreeSet<>(Arrays.asList(5,3,1,8,9,6,2,4,7));
        System.out.println("TreeSet中的所有元素=" + ts);
        System.out.println("TreeSet中第一个元素是=" + ts.first());
        System.out.println("TreeSet中的最后一个元素是=" + ts.last());
        System.out.println("TreeSet中元素小于5的部分是=" + ts.headSet(5));
        System.out.println("TreeSet中元素小于等于5的部分是=" + ts.tailSet(5));
        System.out.println("TreeSet中元素3到8的部分=" + ts.subSet(3,8));

        TreeSet<Student> tsStus = new TreeSet<>();
        Student s1 = new Student(2,"zhang");
        Student s2 = new Student(1,"lisi");
        Student s3 = new Student(3,"wang");
        tsStus.add(s1);
        tsStus.add(s2);
        tsStus.add(s3);

        System.out.println("tsStus中所有的学生=" + tsStus);

        //降序排列
        TreeSet<Student> tsStus2 = new TreeSet<>(new Student.StudentComparator());
        tsStus2.add(s1);
        tsStus2.add(s2);
        tsStus2.add(s3);
        System.out.println("tsStu2中所有的学生=" + tsStus2);

    }
}