java===集合框架之HashSet,treeSet

package 集合框架4.hashSet;

import java.util.HashSet;
import java.util.Iterator;

import 对象库.Person;
import 对象库.Student;

/**
 * hashSet集合：
 * 数据结构为哈希表；因此需要复写hashCode()方法，以此来进行容器内部元素排序
 * 但是哈希值有几率会相同，元素却不同，类如："ab"和"ba" ;所以为了确保Set集合
 * 元素的唯一性，还要进行内容比较，因而需要覆写equals()方法；详见对象库.Person类
 * 特点：无序；元素唯一；
 * */
public class HashSetDemo1 {

    public static void main(String[] args) {
        HashSet<Person> hs1 = new HashSet<Person>();
        hs1.add(new Person("Mr.Smith",19));
        hs1.add(new Person("Mr.Tom",17));
        hs1.add(new Person("Mr.Cokeey",21));
        hs1.add(new Person("Mr.Sky",18));
        HashSet<Student> hs2 = new HashSet<Student>();
        hs2.add(new Student("Mr.Wang",14));
        hs2.add(new Student("Mr.Li",13));
        hs2.add(new Student("Mr.Yang",15));
        hs2.add(new Student("Mr.Anny",12));
        
        hs1.addAll(hs2);
        
        for(Iterator<Person> it1 =hs1.iterator();it1.hasNext();){
            Person p = it1.next();
            System.out.println(p.getName()+":"+p.getAge());
        }

    }

}

package 集合框架3.treeset;

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

import 对象库.Person;
import 比较器.comparator.ComparetorByAge;

public class TreeSetDemo {

    public static void main(String[] args) {
        TreeSet<Person> ts = new TreeSet<Person>(new ComparetorByAge());
        ts.add(new Person("lisi",21));
        ts.add(new Person("wangwu",22));
        ts.add(new Person("zhaoliu",25));
        ts.add(new Person("caiqi",27));
        Iterator<Person> it = ts.iterator();
        while(it.hasNext()){ 
            Person p =/*(Person)可以省略强转原因是：声明Iterator是已经泛型<Person>不是Person对象是不会被操作的*/it.next();
            System.out.println(p.getName()+":"+p.getAge());
        }

    }

}

package 比较器.comparator;
/**集合内添加比较器用于TreeSet集合，TreeMap集合*/
import java.util.Comparator;

import 对象库.Person;

public class ComparetorByAge implements Comparator<Person> {

    public static void main(String[] args) {
        

    }

    @Override
    public int compare(Person o1, Person o2) {
        Person p1 = (Person)o1;
        Person p2 = (Person)o2;
        int temp=p1.getAge()-p2.getAge();//大于0则P1大
        return temp==0?p1.getName().compareTo(p2.getName()):temp;
        //如果temp==0证明年龄相同,则比较name大小String类中覆写了compareTo()方法；如果temp!=0则返回temp;
    }

}

package 比较器.comparator;

import java.util.Comparator;

import 对象库.Person;

public class ComparetorByName implements Comparator<Person> {

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

    }

    @Override
    public int compare(Person o1, Person o2) {
        // TODO Auto-generated method stub
        int temp=o1.getName().compareTo(o2.getName());
        return temp==0?o1.getAge()-o2.getAge():temp;
    }

}

package 对象库;

public class Person {
    public class Student {

    }
    private String name;
    private int age;
    
    public Person(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }
    public Person() {
        super();
    }
    
    @Override
    public boolean equals(Object obj) {
        if(this==obj){
            return true;
        }
        if(!(obj instanceof Person)){
            throw new ClassCastException("类型转换异常");
        }else{
            Person p = (Person)obj;
            return this.name==p.name;
        }
        
    }
    @Override
    public int hashCode() {
        // TODO Auto-generated method stub
        return getName().hashCode()+age*31;
    }
    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;
    }
    

    
}