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();
}
}
}