for Example, lets say i want to use ArrayList so I've to use
import java.util.ArrayList;
in my java source. But in case i forgot that ArrayList is included in java.util package.
so how do i find a package name of ArrayList class ?
I'm not sure what you use for development, but I'm using IntelliJ IDEA and I never have to care about any import statement. I just start to type ArrL and IDEA will take care of the rest. It will suggest ArrayList<E> for autocompletion and fix the import statement instantly. It just knows what you want to do and you can concentrate on development and not on remembering package names:
An easy way to do it in the command-line is to search the src.zip file which comes with the SDK. So if you try to find ArrayList then you can do
7z l src.zip | grep ArrayList
and you get
2013-03-26 21:10:27 ..... 42659 8916 java/util/concurrent/CopyOnWriteArrayList.java
2013-03-26 21:10:27 ..... 21547 5814 java/util/ArrayList.java
where you can see the package structure because it is similar to the sub-folders. I'm sure there are corner-cases where this doesn't work, but you can at least try.
