Arrays类的对象数组的排序练习

Student类

package com.shrimpking.t10;

/**
 * Created by IntelliJ IDEA.
 *
 * @Author : Shrimpking
 * @create 2024/9/6 21:17
 */
public class Student implements Comparable
{

    private int no;
    private String name;

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


    @Override
    public int compareTo(Object o)
    {
        Student stu = (Student)o;
        return this.no > stu.no ? 1 : (this.no < stu.no ? -1 : 0);
    }

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

排序 

package com.shrimpking.t10;

import java.util.Arrays;

/**
 * Created by IntelliJ IDEA.
 *
 * @Author : Shrimpking
 * @create 2024/9/6 21:21
 */
public class ObjectArraySort
{
    public static void main(String[] args)
    {
        Student[] students = new Student[3];
        students[0] = new Student(3,"zhang");
        students[1] = new Student(1,"wang");
        students[2] = new Student(2,"li");

        Arrays.sort(students);
        for (Student student : students)
        {
            System.out.println(student);
        }
    }
}

Student类中的compareTo方法就是对Comparable接口的compareTo方法的实现，在方法内，我们使用了三元运算符“？：”对两个对象的学号进行比较，当然也可以使用if/else if/else语句来进行判断比较。

在对对象数组进行排序时，除了让对象实现Comparable接口外，还可以提供一个单独的比较器对象，用于指定对象间的排序规则。比较器对象是实现了Comparator接口的对象，该接口位于java.util包中，用于比较的方法是compare，该方法接受两个对象参数，判断逻辑与Comparable接口中的compareTo方法一样，当前一个对象小于、等于或者大于后一个对象时，则分别返回负整数、0或者正整数。在Comparator接口中还有一个抽象方法equals，但这个方法可以不用去实现，因为所有的类都是从Object类继承而来的，而Object类就有equals方法，相当于基类替我们实现了equals抽象方法。

Student类

package com.shrimpking.t11;

import java.util.Comparator;

/**
 * Created by IntelliJ IDEA.
 *
 * @Author : Shrimpking
 * @create 2024/9/6 21:28
 */
public class 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 + '\'' + '}';
    }

    static class StudentComparator implements Comparator{

        @Override
        public int compare(Object o1, Object o2)
        {
            Student stu1 = (Student)o1;
            Student stu2 = (Student)o2;
            if(stu1.no > stu2.no){
                return 1;
            }else if(stu1.no < stu2.no){
                return -1;
            }else
            {
                return 0;
            }
        }
    }
}

package com.shrimpking.t11;

import java.util.Arrays;

/**
 * Created by IntelliJ IDEA.
 *
 * @Author : Shrimpking
 * @create 2024/9/6 21:31
 */
public class ObjectArraySort
{
    public static void main(String[] args)
    {
        Student[] students = new Student[3];
        students[0] = new Student(3,"zhang");
        students[1] = new Student(1,"wang");
        students[2] = new Student(2,"li");

        Arrays.sort(students,new Student.StudentComparator());
        for (Student student : students)
        {
            System.out.println(student);
        }
    }
}