Java-TreeSet的用法-入门

Java语言中，Set接口有3种通用实现：HashSet, TreeSet,LinkedHashSet。TreeSet是一种能够对内部元素进行排序的集合，它使用红黑树来存储内部元素，基于元素的值进行排序，它比HashSet要慢。

TreeSet要求内部元素实现Comparable接口，因为它是根据元素的compareTo来排序的。下面是一个demo：

package Colloections;

import java.util.LinkedList;
import java.util.TreeSet;

public class TreeSetDemo {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        TreeSet<Person> treeSet = new TreeSet<Person>();
        treeSet.add(new Person("albert", 8));
        treeSet.add(new Person("bob", 5));
        treeSet.add(new Person("bob", 13));

        for (Person person : treeSet) {
            System.out.printf(person.toString());
        }
    }
}

class Person implements Comparable<Person>{

    public String name;
    public int age;

    public Person(String n, int a){
        name = n;
        age = a;
    }

    public  String toString() {
        return String.format("Name is %s, Age is %d%n", name, age);
    }

    @Override
    public int compareTo(Person o) {
        // TODO Auto-generated method stub
        int nameComp = this.name.compareTo(o.name);
        return (nameComp != 0 ? nameComp : (this.age - o.age));
    }

}

程序输出为：

Name is albert, Age is 8
Name is bob, Age is 5
Name is bob, Age is 13