Java Performance in collection - 02

java.util.Map

Addition and Accession

Hashtable vs. HashMap

Addition

Hashtable ht = new Hashtable();

For(int I = 0; i

{

          ht.put(Integer.valuOf(i),Integer.valueOf(i));

}                                                                                     Takes 453 ms

HashMap hm = new HashMap();

For(int i=0;i

{

          hm.put(Integer.valueOf(i),Integer.valueOf(i));

}                                                                                     Takes 328 ms

Accession

Hashtable ht = new Hashtable();

For(int I = 0; i

{

          ht.get(Integer.valuOf(i));

}                                                                                     Takes 94 ms

HashMap hm = new HashMap();

For(int i=0;i

{

          hm.get(Integer.valueOf(i));

}                                                                                      Takes 47 ms

Hashtable vs. HashMap

Hashtable is synchronized so it is slower than HashMap

Exceptions, assertions, casts and variables

•Include all error-condition checking in blocks guarded by if statements

•Avoid throwing exceptions in normal code path of your application

•Investigate whether a try-catch in the bottleneck imposes any extra cost

•Use instanceof instead of making any speculative class cast in a try-catch

•Consider throwing exceptions without generating a stack trace by reusing a previously created instance

•Assertions add overheads, even when disabled

•Avoid (or do not use) assertions in a loop, frequently called methods

•Avoid casts by using type specific collection classes

•Use temporary variables of the cast type, instead of repeated casting

•Prefer local variables to instance/static variables for faster manipulation

•Use int in preference to any other datatypes

•Prefer primitive datatypes instead of objects for temporary variables