observations in case of Map

[Saral Saxena]

Hi Folks,,
I was going through Map ...I have observed in my below piece of code that if we try to have same key then the latest key overrides the value of previous key while iterating..Now my query is that can Map accept duplicate keys that is ok ...but does it accept duplicate keys with duplicate values..can you advise me in which case the map throws the error if we play with Map...!!

 HashMap map=new HashMap();//HashMap key random order.
         map.put("Amit","Java");
          map.put("Saral","J2EE");
         map.put("","Spring");
         map.put("Anupam","Hibernate");
         map.put("Ravi",".Net");
         map.put("Saral","Andriod");//same key but different value 
         map.put("Nitin","PHP");
         map.put("","Spring1");
         System.out.println("There are "+map.size()+" elements in the map.");
         System.out.println("Content of Map are...");
         Set s=map.entrySet();
         Iterator itr=s.iterator();
         while(itr.hasNext())
         {
             Map.Entry m=(Map.Entry)itr.next();
             System.out.println(m.getKey()+"\t"+m.getValue());
          }

The result that I am getting ..

There are 6 elements in the map.
Content of Map are...
Nitin PHP
Spring1
Anupam Hibernate
Ravi .Net
Amit Java
Saral Andriod

Please advise..!!

[Pramod P Deore]

.Now my query is that can Map accept duplicate keys that is ok ...but does it accept duplicate keys with duplicate values..can you advise me in which case the map throws the error if we play with Map...!!

Yes it accept duplicate keys with duplicate values.By definition, the put command replaces the previous value associated with the given key in the map.

[Martin Vajsar]

Please see documentation of the java.util.Map interface. I'd also strongly suggest reading the Collections Framework tutorial, specifically this page.

[Saral Saxena]

Pramod P Deore wrote:

.Now my query is that can Map accept duplicate keys that is ok ...but does it accept duplicate keys with duplicate values..can you advise me in which case the map throws the error if we play with Map...!!

Yes it accept duplicate keys with duplicate values.By definition, the put command replaces the previous value associated with the given key in the map.

Yeah but please guide me in which cases Map can throw exceptions..!! thanks in advance..!!

[Matthew Brown]

Why are you expecting it to throw an exception?

[Saral Saxena]

Matthew Brown wrote:Why are you expecting it to throw an exception?

Just to enhance my knowledge ...is there any case in which Map throws exception..??

[Henry Wong]

Saral Saxena wrote:

Matthew Brown wrote:Why are you expecting it to throw an exception?

Just to enhance my knowledge ...is there any case in which Map throws exception..??

For questions like these, the javadoc is the best place to look -- java.util.Map.

Henry

[Jeff Verdegan]

Saral Saxena wrote:

Matthew Brown wrote:Why are you expecting it to throw an exception?

Just to enhance my knowledge ...is there any case in which Map throws exception..??

In addition to reading the javadocs as already suggested, keep in mind that any method in class can throw an unchecked exception any time you call it.