Java interview questions: 1. Can we create an Object class in java? 2. There is one duplicate number in an array of 100 numbers. How to find the duplicate number? 3. Difference between arraylist and vector. we have a class with class members and local varibales. where should use vector and where should use arraylist and why? 4. what happens when an uncaught exception occurs in a thread. Invoking thread and others sibling threads will continue running? 5. hashtable and hashmap difference. how objects are stored in them. hashcode and equals. why need to overwrite equals if hashcode is overwritten. 6. what all patterns you know. explain about singleton pattern. can we serialize singleton object? give supporting reason for your answer. 7. what is mergesort. this question he asked because I have written algorithms in my area if interests.