>>>> What is the best methods or stratergy present to debug the java errors?
Fix 'em !
Compile errors - the advice is simple - learn how to read the debug erorrs and info (ie identify the class, find the line and fix it).
Runtime errors - These are a little harder to debug, but the statck trace of the error should show you which class died, in which method - you can then start looking for code which could have thrown that particular error.
Obviously the best practice is write your code in a tight manner, catching any forseeable errors, and printing them out to the screen with helpful messages. This way, you will hopefully be in a situation where you never get errors which leave you scratching your head (yeah right!) !