/*
TreeSet集合是Set集合的一个子实现类,它是基于TreeMap中的NavigableSet接口实现的

TreeSet集合是默认通过自然排序将集合中的元素进行排序

TreeSet有两种排序方式:

     1)自然排序

  2)比较器排序
 */ 
public class Student implements Comparable<Student> {

    private String name;
    private int age;

    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 + "]";
    }
    public Student() {
        super();
    }
    public Student(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }    /*
     * 在compareTo()方法中要实现Student类型的排序规则,指定排序规则 首先按照age升序排列 age相同,按照name升序排序
     */
    @Override
    public int compareTo(Student o) {
        //如果该对象小于等于或者大于指定对象,则分别返回负整数,零或者正整数
        if (this.age < o.age) {
            return -1;
        }else if (this.age > o.age) {
            return 1;
        }    
        if (this.name.compareTo(o.name) > 0) {
            return 1;
        }else if (this.name.compareTo(o.name) < 0) {
            return -1;
        }        
        return 0;
    }
}

 

import java.util.TreeSet;
//TreeSet可以保证添加到其中的String类型的数据不可重复且可以排序
public class TreeSetTest {    
    /*
     * 我们要把Student类型的数据添加到TreeSet中,则Student要实现comparable接口并且要实现其中的compareTo()方法
     * 在compareTo()方法中要实现Student类型的排序规则
     * 当我们把Student类型的数据向TreeSet中添加的时候,TreeSet会自动的调用Student对象的compareTo()方法
     * 如果compareTo()方法返回0,则不让数据进入集合;然后根据compareTo()方法返回负数/正数对象数据进行排序
     */
    public static void test(){
    Set<Student> set = new TreeSet<Student>(); 
    Student stu1 = new Student("aa",21);
    Student stu2 = new Student("bb",21);
    Student stu3 = new Student("aa",22);
    Student stu4 = new Student("aa",23);
    Student stu5 = new Student("dd",24);
    Student stu6 = new Student("ee",25);
    Student stu7 = new Student("ee",26);
    Student stu8 = new Student("ff",24);
    Student stu9 = new Student("aa",21);
    
    set.add(stu1);
    set.add(stu2);
    set.add(stu3);
    set.add(stu4);
    set.add(stu5);
    set.add(stu6);
    set.add(stu7);
    set.add(stu8);
    set.add(stu9);
    
    System.out.println("集合中数据的个数:" + set.size());    
    for (Student st : set) {
        System.out.println(st);
    }    
}
    public static void main(String[] args) {
        test();
    }    
}

运行结果:

集合中数据的个数:8

Student [name=aa, age=21]
Student [name=bb, age=21]
Student [name=aa, age=22]
Student [name=aa, age=23]
Student [name=dd, age=24]
Student [name=ff, age=24]
Student [name=ee, age=25]
Student [name=ee, age=26]<2>
public class Student{

    private String name;
    private int age;

    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 + "]";
    }
    public Student() {
        super();
    }
    public Student(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }
}
import java.util.Comparator;
//实现学生降序排列的比较器
public class StudentComparator1 implements Comparator<Student> {

    @Override
    public int compare(Student o1,Student o2) {
        //根据第一个参数小于,等于或大于第二个参数分别返回负整数,零或正整数
        if (o1.getAge() > o2.getAge()) {
            return -1;
        }else if (o1.getAge() < o2.getAge()) {
            return 1;
        }
        
        if(o1.getName().compareTo(o2.getName()) > 0){
            return -1;
        }else if (o1.getName().compareTo(o2.getName()) < 0) {
            return 1;
        }
        return 0;
    }

}

 

import java.util.Comparator;
//实现学生升序排列的比较器
public class StudentComparator2 implements Comparator<Student> {

    @Override
    public int compare(Student o1,Student o2) {
        //根据第一个参数小于,等于或大于第二个参数分别返回负整数,零或正整数
        if (o1.getAge() > o2.getAge()) {
            return 1;
        }else if (o1.getAge() < o2.getAge()) {
            return -1;
        }
        
        if(o1.getName().compareTo(o2.getName()) > 0){
            return 1;
        }else if (o1.getName().compareTo(o2.getName()) < 0) {
            return -1;
        }
        return 0;
    }

}

 

 

 

import java.util.Set;
import java.util.TreeSet;

//TreeSet可以保证添加到其中的String类型的数据不可重复且可以排序
public class TreeSetTest {    
    /*
     * 我们要把Student类型的数据添加到TreeSet中,则Student要实现comparable接口并且要实现其中的compareTo()方法
     * 在compareTo()方法中要实现Student类型的排序规则
     * 当我们把Student类型的数据向TreeSet中添加的时候,TreeSet会自动的调用Student对象的compareTo()方法
     * 如果compareTo()方法返回0,则不让数据进入集合;然后根据compareTo()方法返回负数/正数对象数据进行排序
     */
    public static void test(){
    
    //Set使用升序规则的比较器
    Set<Student> set = new TreeSet<Student>(new StudentComparator1());
    
    Student stu1 = new Student("aa",21);
    Student stu2 = new Student("bb",21);
    Student stu3 = new Student("aa",22);
    Student stu4 = new Student("aa",23);
    Student stu5 = new Student("dd",24);
    Student stu6 = new Student("ee",25);
    Student stu7 = new Student("ee",26);
    Student stu8 = new Student("ff",24);
    Student stu9 = new Student("aa",21);
    
    set.add(stu1);
    set.add(stu2);
    set.add(stu3);
    set.add(stu4);
    set.add(stu5);
    set.add(stu6);
    set.add(stu7);
    set.add(stu8);
    set.add(stu9);
    
    System.out.println("集合中数据的个数:" + set.size());    
    for (Student st : set) {
        System.out.println(st);
    }    
}
    public static void main(String[] args) {
        test();
    }    
}

 

 

运行结果:

集合中数据的个数:8

Student [name=ee, age=26]
Student [name=ee, age=25]
Student [name=ff, age=24]
Student [name=dd, age=24]
Student [name=aa, age=23]
Student [name=aa, age=22]
Student [name=bb, age=21]
Student [name=aa, age=21]