Velocis Systems interview question

Q1. Explain JDK, JRE and JVM? Q2. Explain public static void main(String args[]) in Java Q3. Why Java is platform independent? Q4. Why Java is not 100% Object-oriented? Q5. What are wrapper classes in Java? Q6. What are constructors in Java? Q7. What is singleton class in Java and how can we make a class singleton? Q8. What is the difference between Array list and vector in Java? Q9. What is the difference between equals() and == in Java? Q10. What are the differences between Heap and Stack Memory in Java?