Impartent Core java Interview questions

I. Introduction to java




1. Why pointers are eliminated from java?

2. What is difference between function and method?

3. Is java purely object oriented language or not?

4. Which part of JVM will allocate the memory for a java program?

5. Which algorithm is used by garbage collector to remove the unused variables or objects from memory?

6. How can you call the garbage collector?

7. What is JIT compiler?



II. First step towards java programming



1. What is an API document?

2. What is difference between #include and import statement?

3. What happens if String args[] is not written in main() method?

4. What is difference between print () and println() method?



III. Naming conventions and data types



1. What is difference between float and double?

2. What is Unicode system?



IV Operators in java



1. How are positive and negative numbers represented internally?

2. What is different between >> and>>>?



V. Control statements in java



1. What are control statements?

2. Out of do. while and while which loop is effective?

3. What is a collection?

4. Why go to statements are not available in java?

5. What is difference between return and System. exit (0)?

6. What is difference between System. exit (0) and System. exit (1)?



VI. Input and output



1. What is difference between System. out and System. err?



VII. Arrays



1. On which memory, arrays are created in java?

2. Can you call the main () method of a class from another class?



VIII Strings



1. Is string a class or data type?

2. Can we call a class as a data type?

3. What is object reference?

4. What is difference between ‘=’ and equals () while comparing string?

5. Which one is reliable?

6. What is string content pool?

7. Explain difference between the following two statements?

• String s = ”Hello”;

• String s = new String(“Hello”);



IX. String buffer and string builder



1. What is difference between string and string buffer classes?

2. Are there any other classers whose objects are immutable?

3. What is difference between string buffer and string builder classes?



X. Introduction to OOPs



1. What is object oriented approach?

2. What id difference between class and object?

3. What is difference between object oriented programming languages and object based programming languages?

XI. Classes and objects



1. What is hash code?

2. How can you find the hash code of an object?

3. Can you declare a class as a private?

4. When is constructor called, before or after creating object?

5. What is difference between default constructor and parameterized constructor?

6. What is difference between constructor and method?

7. What is constructor overloading?



XII. Method in Java



1. What are instance methods?

2. What are static methods?

3. What is difference between instance variables and class variables (static variables)?

4. Why instance variables not available to static methods?

5. Is it possible to compile and run a java program with out writing main () method?

6. How are objects passed to methods in java?

7. What are factory methods?

8. In how many ways can you create an object in java?