Core Java

1. Java 7 new features
2. Super and This Key word in Java
3. Boxing and widening in Java--which one is preferred ?
4. How Constructor call flow happen in Inheritence?
5. Static and Dynamic polymorphism
6. Behavior of Object references in Java 
7. Pass by Value Pass by reference in Java
8. Comparable and Comporator interfaces in Java
9. Role of Access modifiers in Java
   
   

Strings and its related concepts :-

1. String-StringBuffer-StringBuilder
2. How hash code gets generated for Strings?
3. String literal pool in Java

Exceptions in Java :-

1. Custom Exceptions in Java
2. Exceptions in Java .
3. Try_Catch_Finally block in Java

File reading and writing :-

1. Reading and writing data in .xls file using Java
2. Reading and Writing Data from/to .xlsx file in Java
3. Using Buffered Reader and Writer--File reader and writer