In several examples so far, I have shown you how to create objects using the new keyword, but you have never seen code that explicitly destroys unused objects to release memory space. If you are a C++ programmer you may have wondered if I had shown flawed code, because in C++ you must destroy objects after use.
Java comes with a garbage collector, which destroys unused objects and frees memory. Unused objects are defined as objects that are no longer referenced or objects whose references are already out of scope.
With this feature, Java becomes much easier than C++ because Java programmers do not need to worry about reclaiming memory space. This, however, does not entail that you may create objects as many as you want because memory is (still) limited and it takes some time for the garbage collector to start. That’s right, you can still run out of memory.
Learn to code Android 