Problem in Creating HashMap object then display in sorted and unsorted order

[sarrah gerard]

Hi All,
I'm really confused in that error
run:
Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
at myhashmap.MyHashMap.main(MyHashMap.java:44)
Java Result: 1

Create your own NetBeans project named as MyHashMap

Create your own HashMap object

Add the following objects to the newly created HashMap object.

2 String objects with keys "1st", "2nd"

2 MyOwnClass objects with keys "3rd", "4th"

1 Integer ojbects with keys "5th"

Display them in both unsorted and sorted order

I tried to write this;
________________________________________________

 package myhashmap;
import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;
import java.util.Set;
import java.util.Iterator;
/**
*
* @author sarah
*/
public class MyHashMap {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
Map hm = new HashMap();
String[] a= new String[5];
MyOwnClass o1 = new MyOwnClass("aa");
MyOwnClass o2 = new MyOwnClass("bb");
hm.put("1sth" , new String("Java"));
hm.put("2nd" , new String("Passion"));
hm.put("3rd", o1);
hm.put("4th", o2);
hm.put("5th", new Integer(9));
//Get HashMap in Set interface to get key and value
Set s=hm.entrySet();
Iterator it = s.iterator();
while(it.hasNext()){
Map.Entry m =(Map.Entry) it.next();
String key= (String) m.getKey();
String value =(String) m.getValue();
hm.put(key, value);
}
System.out.println("UnSorted order is : " + hm);
Map sortedMap = new TreeMap(hm);
System.out.println("Sorted map " + sortedMap);
}
}

_____________________________________________________________

package myhashmap;
/**
*
* @author sarah
*/
public class MyOwnClass extends MyHashMap{
String X;
public MyOwnClass()
{
}
public MyOwnClass(String X)
{
this.X = X;
}
@Override
public String toString() //this part is important
{
return X;
}
}

__________________________________________
There are lots of reference as you see, Please help to arrenge my code:(

[Embla Tingeling]

The problem is that you put in mixed type objects in the HashMap (such as String, Integer and MyOwnClass). Then when you retreive them you cast to String. This give you the ClassCastException.

[Lee Kian Giap]

This is the problem

String value =(String) m.getValue();

when you getValue() from the map, it can be String object, Integer object or MyOwnClass object, so you can't simply cast everything to String.


Try this

String value = m.getValue().toString();

[sarrah gerard]

 

Embla Tingeling wrote:The problem is that you put in mixed type objects in the HashMap (such as String, Integer and MyOwnClass). Then when you retreive them you cast to String. This give you the ClassCastException.

Thanks Embla,
I add like this, after your arrangement

package myhashmap;
import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;
import java.util.Set;
import java.util.Iterator;
[color=brown]import java.util.Comparator;[/color]
/**
*
* @author sarrah
*/
public class MyHashMap {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
[color=brown] Map hm = new HashMap(new Comparator()){
public int compare(Object o1, Object o2) {
return String.valueOf(o1).compareTo(String.valueOf(o2));
}
};[/color]
String[] a= new String[5];
.
.
.

__________________________________
now the error turns in to
run:
Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - java.util.Comparator is abstract; cannot be instantiated
at myhashmap.MyHashMap.main(MyHashMap.java:26)
Java Result: 1
I think ,i am placed to wrong line. but, i don't know the correct way

[sarrah gerard]

 

Lee Kian Giap wrote:This is the problem

String value =(String) m.getValue();

when you getValue() from the map, it can be String object, Integer object or MyOwnClass object, so you can't simply cast everything to String.


Try this

String value = m.getValue().toString();

wooow you're right. now it runs
run:
UnSorted order is : {2nd=Passion, 1sth=Java, 5th=9, 3rd=aa, 4th=bb}
Sorted map {1sth=Java, 2nd=Passion, 3rd=aa, 4th=bb, 5th=9}
Thanks thanks a lot, with my Regards Lee Kian Giap )

[Rob Spoor]

Sarrah, welcome to JavaRanch

Could you try to Use Code Tags in the future? Thanks.

[sarrah gerard]

 

Rob Prime wrote:Sarrah, welcome to JavaRanch

Could you try to Use Code Tags in the future? Thanks.

hahah ok ,i did,sorry
thanks Rob Prime