1.  Explain about Java?

Ans: Java is a high-level programming language originally developed by Sun Microsystems and released in 1995. Java runs on a variety of platforms, such as Windows, Mac OS, and the various versions of UNIX.

Ans: OOPs stand for Object Oriented Programming organizes a program around its data.  An object-oriented program can be characterized as data controlling access to code.

3.  What is the purpose of garbage collection in Java?

Ans: The purpose of garbage collection is to discover and discard objects that are no longer needed by a program so that their resources can be reclaimed and reused.

4.  What is meant by an Object?

Ans: Object is a runtime unit and its state is stored in fields and performance is shown via methods. Methods operate on an object's internal state and serve as the primary mechanism for object-to-object communication. 

5.  Define static in java?

Ans: Static means one per class, not one for each object no matter how many instance of a class might exist. This means that you can use them without creating an instance of a class. Static methods are totally final, because overriding is done based on the type of the object, and static methods are attached to a class, not an object. A static method in a superclass can be shadowed by another static method in a subclass, as long as the original method was not declared final.  

              

6. What is an Object and how do you allocate memory to it?

Ans: Object is an example of a class and it is a software unit that combines a prepared set of data with a set of operations for inspecting and manipulates that data. When an object is created using new operator, memory is allocated to it.

7.  Define class in Java?

Ans: A class is a blue print from which individual objects are created. A class can have fields and methods to describe the behavior of an object.

8.  Why String class is considered immutable?

Ans: The String class is immutable; so that once it is created a String object cannot be changed. Since String is immutable it can safely be shared between many threads. 

9.  What is an Iterator?

Ans: Some of the collection classes provide traversal of their contents. This interface allows you to walk through a collection of objects, operating on each object in turn. 

10. Define Runtime Exceptions?

Ans: It is an exception that occurs that most likely could have been avoided by the programmer. As opposed to checked exceptions, runtime exceptions are ignored at the time of compilation.