映射Map

本篇介绍java.util.Map接口下的两个方法HashMap与Hashtable

HashMap与Hashtable的区别在于状态，前者：非同步；后者：同步（线程）

        注：HashMap笔者认为是无序映射集合，Hashtable是按添加顺序排列(未证实)

1.HashMap>>

package cn.test.map;

import java.util.Collection;
import java.util.HashMap;
import java.util.Set;
import java.util.Map.Entry;

public class TestHashMap {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        HashMap hm = new HashMap();
        hm.put(10, new Person("小沈阳", 20, "中国"));
        hm.put(2, new Person("沈阳", 20, "日本"));
        hm.put(40, new Person("小沈", 20, "美国"));
        hm.put(25, new Person("小阳", 20, "英国"));
        //去键存入Set中
        Set s = hm.keySet();
        for (int i : s) {
            System.out.println(i);
        }
        //取值存入Collection
        Collection c = hm.values();
        for (Person p : c) {
            System.out.println(p.getName());
        }
        //转换成set集合(键值对)
        Set> st = hm.entrySet();
        for(Entry e:st)
        {
            Person p=e.getValue();
            System.out.println(e.getKey()+"\t"+p.getName()+"\t"+p.getAge()+"\t"+p.getAddress());
        }
    }

}

2.Hashtable>>

package cn.test.map;

import java.util.Collection;
import java.util.Hashtable;
import java.util.Set;
import java.util.Map.Entry;

public class TestHashTable {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Hashtable ht = new Hashtable();
        ht.put(32, new Person("小沈阳", 20, "北京"));
        ht.put(102, new Person("赵本山", 23, "辽宁"));
        ht.put(22, new Person("老胡", 76, "未知"));
        Set s = ht.keySet();
        for (Integer i : s) {
            System.out.println(i);
        }
        Collection c = ht.values();
        for (Person p : c) {
            System.out.println(p.getName() + "\t" + p.getAge() + "\t"
                    + p.getAddress());
        }
        Set> se = ht.entrySet();
        for (Entry e : se) {
            Person p = e.getValue();
            System.out.println(e.getKey() + "\t" + p.getName() + "\t"
                    + p.getAge() + "\t" + p.getAddress());
        }
    }

}

附：Person类

package cn.test.map;

public class Person {
    private String name;
    private int age;
    private String address;

    public void setName(String name) {
        this.name = name;
    }

    public String getName() {
        return this.name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public Person(String name, int age, String adress) {
        this.name = name;
        this.age = age;
        this.address = adress;
    }
}