java Map 操作

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


public class MapOperate {

	public static void main(String[] args) {
		Map<String,Student> map1 =new HashMap<String,Student>();
		map1.put("s1", new Student("1",99));
		map1.put("s2", new Student("2",88));
		map1.put("s3", new Student("3",77));
		
		Map<String,Student> map2 =new HashMap<String,Student>();
		map2.put("s4", new Student("4",99));
		map2.put("s5", new Student("5",88));	
		map1.putAll(map2);
		
		/*
		 * 1.
		 */
		Collection<Student> c = map1.values();
		Iterator<Student> it1 = c.iterator();
		while(it1.hasNext())
			System.out.println(it1.next().id);
		
		/*
		 * 2.
		 */
		Set<String> s = map1.keySet();
		Iterator<String> it2 = s.iterator();
		while(it2.hasNext())
			System.out.println(map1.get(it2.next()).id);
	}

}

class Student{
	String id;
	int score;
	public Student(String id, int score){
		this.id=id;
		this.score=score;
	}
}