JAVA Map

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

public class text2 {

	public static void main(String[] args) {
		
		Map map = new HashMap();
		
		map.put("String", "这是一个字符串");
		map.put("Object", new Object());
		map.put("int", 1234);
		map.put(1, 1);
		map.put(new Object(), new Object());
		map.put(null , null);
		
		
		Set set = map.keySet();
		Iterator it = set.iterator();
		while(it.hasNext()){
			System.out.println(it.next());
		}
	}
}