Dumping HashMAp

[Sridhar]

Consider the following snippet to display the contemts of a HashMap in
a sequential manner.

//temp2 is a hashmap
Set set2=temp2.entrySet();
Iterator iHash2=set2.iterator();

while(iHash2.hasNext()){
Map.Entry me2= (Map.Entry) iHash2.next();
System.out.println(me2.getKey());
}

I printed the order in which the elements were entered in the HashMap
and later printed the hashMap using the above algorithm... both are
different.... Any idea why??

I'm just printing the keys here. During insertion the order followed
for the key is
r1,s3,s2,s1

but when i print the hashmap the order is:
s2,s3,r1,s1

Since i need to use it sequentially later in the application, the order
is very important. I cant sort the hashmap too as keys have no relation
whatsoever.

Any pointers??

 

[Ingo R. Homann]

Hi,

I printed the order in which the elements were entered in the HashMap
and later printed the hashMap using the above algorithm... both are
different.... Any idea why??

Because HashMap does not say anything about the order! (Are you sure,
you understand what a HashMap does? If not, do not use it, especially
not with own objects, because you may be surprised about different
issues as well!)

Perhaps, SortedMap / TreeMap can help you. Otherwise, a
(Array-/Linked)List might be what you are looking for.

Ciao,
Ingo

 

[Ace]

Try LinkedHashMap

Hi,


Because HashMap does not say anything about the order! (Are you sure,
you understand what a HashMap does? If not, do not use it, especially
not with own objects, because you may be surprised about different
issues as well!)

Perhaps, SortedMap / TreeMap can help you. Otherwise, a
(Array-/Linked)List might be what you are looking for.

Ciao,
Ingo

 

[Sridhar]

I guess you are right... I made the blunder of assuming that the order
of the elements will be maintained. Will surely try out the other
alternatives. Thanx everyone

 

[Joan]

Consider the following snippet to display the contemts of a HashMap in
a sequential manner.

//temp2 is a hashmap
Set set2=temp2.entrySet();
Iterator iHash2=set2.iterator();

while(iHash2.hasNext()){
Map.Entry me2= (Map.Entry) iHash2.next();
System.out.println(me2.getKey());
}

I printed the order in which the elements were entered in the HashMap
and later printed the hashMap using the above algorithm... both are
different.... Any idea why??

I'm just printing the keys here. During insertion the order followed
for the key is
r1,s3,s2,s1

but when i print the hashmap the order is:
s2,s3,r1,s1

Use TreeMap instead.

 

[Sridhar]

Used LinkedHashMAp... It did the trick