Comparable接口的使用方法--例子

朴灿烈づ我的快乐病毒、 2024-02-18 21:58 7阅读 0赞

1.创建Student类

package com.test.collection;
    
    //创建Student类并实现Comparable接口，Comparable<Student>限定比较的对象为Student
    public class Student implements Comparable<Student> {
    	public static String school;
    	private String stuName;
    	private int age;
    	private String major;
    
    	public Student(String stuName, int age, String major) {
    
    		this.stuName = stuName;
    		this.age = age;
    		this.major = major;
    	}
    
    	public Student() {
    
    		// TODO Auto-generated constructor stub
    	}
    
    	public String getStuName() {
    		return stuName;
    	}
    
    	public void setStuName(String stuName) {
    		this.stuName = stuName;
    	}
    
    	public int getAge() {
    		return age;
    	}
    
    	public void setAge(int age) {
    		if (age >= 18 && age <= 100) {
    			this.age = age;
    		} else {
    			System.err.println("年龄输入非法！");
    		}
    	}
    
    	public String getMajor() {
    		return major;
    	}
    
    	public void setMajor(String major) {
    		this.major = major;
    	}
    
    	public void sayHello() {
    		System.out.println("大家好！我叫" + this.stuName + "，今年" + age + "岁了。");
    	}
    
    	// 重写toString方法
    	@Override
    	public String toString() {
    		return "Student [stuName=" + stuName + ", age=" + age + ", major=" + major + "]";
    	}
    
    	// 因为实现了Comparable接口，必须重写compareTo方法
    	@Override
    	public int compareTo(Student o) {
    	
    		//如果被比较对象的年龄o.age大于this.age,返回1
    		//如果被比较对象的年龄o.age小于this.age,返回-1
    		//通过修改返回值，可以实现升序或降序排序
    		if (this.age < o.age) {
    			return -1;
    		} else if (this.age > o.age) {
    			return 1;
    		}
    		return 0;
    	}
    
    }

2.创建测试类TestComparable

package com.test.collection;
    
    import java.util.ArrayList;
    import java.util.Collections;
    import java.util.List;
    
    public class TestComparable {
    
    	public static void main(String[] args) {
    		// TODO Auto-generated method stub
    		List<Student>  stuList =new ArrayList<Student>();
    		Student s1 = new Student("张三",30,"软件工程");
    		Student s2 = new Student("李四",19,"软件工程");
    		Student s3 = new Student("王五",40,"软件工程");
    		//把s1,s2,s3三个Student实例，添加到stuList中
    		stuList.add(s1);
    		stuList.add(s2);
    		stuList.add(s3);
    		System.out.println("排序前：");
    		//使用foreach遍历stuList，并调用stuList中每个对象的sayHello()方法
    		for (Student s : stuList) {
    			s.sayHello();
    		}
    		
    		//使用Collections.sort排序，一个参数情况下是List实例名
    		//使用此方法排序父类要实现Comparable接口并重写compareTo方法
    		//通过重写compareTo方法，修改返回值，可以实现升序或降序排序
    		System.out.println("升序排序后：");
    		Collections.sort(stuList);
    		for (Student s : stuList) {
    			s.sayHello();
    		}
    		
    	}
    
    }