Object oriented concepts understanding is must for doing java programming easily. Mastering of APIs, the way they developed to use it in java programming makes one can be master in java language. This book is written exclusively from student dimension after taking into consideration of difficulties and problems of learning in a given semester with in a limited time. The Book is to master fundamentals and some important basic insights of APIs to do programming easily. The interest in this subject comes as I had worked in Singapore for 3 years in java technologies and also java certified in 2001 in Singapore and Microsoft Certified in 1999 in India. This book covers core Java topics into 5 chapters which is the most common to all Universities in India and Abroad. This book can be very much useful for Teachers teaching first time Java language. This book useful for UG ,PG and other higher schooling students interested in java programming to develop the applications.