集合框架-TreeSet集合

package cn.itcast.p5.treeset.demo;

import java.util.Iterator;
import java.util.TreeSet;

import cn.itcast.p.bean.Person;

public class TreeSetDemo {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
//        demo1();
        TreeSet ts = new TreeSet(/*new ComparatorByName()*/);//比较器排序优先于person的自然排序，实际开发比较器常用，person一般会实现comparator接口
        /*
         * 以Person对象的年龄进行从小到大的排序。
         * 
         */
        ts.add(new Person("zhangsan",28));
        ts.add(new Person("wangwu",29));
        ts.add(new Person("lisi",21));
        ts.add(new Person("zhouqi",29));
        ts.add(new Person("zhaoliu",25));//Person cannot be cast to class java.lang.Comparable
        
        Iterator it = ts.iterator();
        
        while(it.hasNext()) {
            Person p = (Person)it.next();
            
            System.out.println(p.getName()+":"+p.getAge());
        }
    }

    

    /**
     * 
     */
    public static void demo1() {
        TreeSet ts = new TreeSet();
        
        ts.add("abc");
        ts.add("zaa");
        ts.add("aa");
        ts.add("nba");
        ts.add("cba");
        
        Iterator it = ts.iterator();
        
        while(it.hasNext()) {
            System.out.println(it.next());
        }
    }

}

package cn.itcast.p.bean;

public class Person /*treeset用*/implements  Comparable {
    private String name;
    private int age;
    
    
    public Person() {
        super();
        // TODO Auto-generated constructor stub
    }
    public Person(String name, int age) {
        super();
        this.name = name;
        this.age = age;
        
    }
    
    @Override
    public int hashCode() {
        System.out.println(this+".....hashCode");
        // TODO Auto-generated method stub
        return name.hashCode()+age*27;//age后面乘以一个数增大离散程度，减少返回哈希值相等的几率
                                    //好比张三哈希值20 年龄40  李四哈希值30，年龄30 结果哈希值一样
                                    //乘一个数后就不一样了离散程度变大了
        
        
        //return 100;//会比较equals
    }
    public boolean equals(Object obj) {
        //健壮性
        if (this == obj) {//有可能传入相同的对象，可以先行判断是否为同一对象add(p) add(p)这种传入两次
            return true;
        }
        if (!(obj instanceof Person)) {//判断是否为Person类型，类型不一致也不应该传入
            throw new ClassCastException("类型错误");
        }
        
//        System.out.println(this+"...equals...."+obj);
        Person p = (Person)obj;
        
        
        return this.name.equals(p.name) && this.age == p.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;
    }
    //ctrl+alt+s 快捷构造set，get方法 初始化等
    public String toString() {
        return name+":"+age;
    }
    @Override
    public int compareTo(Object o) {//对象的自然排序(treeset)
        // TODO Auto-generated method stub
        Person p = (Person)o;
        int temp = this.age - p.age;
        return temp==0?this.name.compareTo(p.name):temp;//主要条件次要条件，以年龄
        
//        int temp = this.name.compareTo(p.name);
//        return temp==0?this.age-p.age:temp;//以名字为主要条件
        /*
         * if (this.age>p.age) 
         * return 1;
         * 
         * if (this.age<p.age)
         *  return -1; 
         * if (this.age == p.age) {
         *  return this.name.compareTo(p.name);
         *  }
         */
        
    }
}

 见集合框架TXT