97 is the byte value of 'a'. Your read() call just got a single byte and converted it to int.

In any case, it's irrelevant. Without a stated encoding expectation, "asu" cannot be converted to int. Integer.parseInt() will convert a valid integer string to an int value. If you want to convert some other string to an int, there are many different ways to do so, but they are specific encoding methods - not just a general api call or statement.

even if you write Integer.parsrInt("asu"); you will get Number format exception but if you write Integer.parseInt("197") it will give the number 197.

Of course, which is already mentioned. You are missing the entire point.

Integer.parseInt() was already explained. The real point is that there is no generic method to make "asu" an int. It is totally dependent upon how you need to encode the string and that is totally dependent on what you intend to use it for.