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java.util.Map
Addition and Accession
Hashtable vs. HashMap
Addition
Hashtable
ht = new Hashtable();
For(int I =
0; i<loop;i++)
{
ht.put(Integer.valuOf(i),Integer.valueOf(i));
} Takes
453 ms
HashMap hm
= new HashMap();
For(int
i=0;i<loop;i++)
{
hm.put(Integer.valueOf(i),Integer.valueOf(i));
} Takes
328 ms
Accession
Hashtable
ht = new Hashtable();
For(int I =
0; i<loop;i++)
{
ht.get(Integer.valuOf(i));
} Takes
94 ms
HashMap hm
= new HashMap();
For(int
i=0;i<loop;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
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