package Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
public class Test {
public static void main(String[] args) {
userful[] userfuls={
new userful(),
new moreUseful()
};
//((moreUseful)userfuls[1]).c();//è¿è¡Œæ—¶ç±»åž‹è¯†åˆ«
//((moreUseful)userfuls[0]).c();
Map map=new HashMap();
//å…许值为null
map.put(1, 1);
map.put(2,null);
map.put(null, 3);
Map map1=new HashMap();
//å…许值为null
map1.put(1, 1);
map1.put(2,null);
map1.put(null, 3);
Set> set=map1.entrySet();
for(Entry entry:set){
System.out.println(entry);
}
//比较里é¢çš„键值
System.out.println("map equals map1:"+map.equals(map1));
}
}
class userful{
public void a(){}
public void b(){}
}
class moreUseful extends userful{
public void a(){}
public void b(){}
public void c(){}
}