HashMap 使用例子

import java.util.HashMap;
import java.util.HashSet;

import java.util.Iterator;

public class HashMapTest {

public static void main(String[] args){
HashMap<String,Object> hm=new HashMap<String,Object>();

People p1=new People();
People p2=new People();
People p3=new People();
People p4=new People();

hm.put("People3", p1);
hm.put("People1", p2);
hm.put("People4", p3);
hm.put("People2", p4);

Iterator<String> it=hm.keySet().iterator();

while(it.hasNext()){
System.out.println(it.next());
}
}
}
class People {
private String name;
private int age;
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}

/*第一种:
　　Map map = new HashMap();
　　Iterator iter = map.entrySet().iterator();
　　while (iter.hasNext()) {
　　Map.Entry entry = (Map.Entry) iter.next();
　　Object key = entry.getKey();
　　Object val = entry.getValue();
　　}
　　效率高,以后一定要使用此种方式！
第二种:
　　Map map = new HashMap();
　　Iterator iter = map.keySet().iterator();
　　while (iter.hasNext()) {
　　Object key = iter.next();
　　Object val = map.get(key);
　　}
　　效率低,以后尽量少使用！*/