Frequently asked Questions in Java Interviews

There are many frequently ask questions on Java Technology. I am discussing first interview question on Java Technology asked by every interviewer. The question is about Difference between Java, C & C++.

Difference between Java and C

Java is not like C but the major difference between Java and C is that Java an object Oriented language. It has a mechanism to define classes and objects. In effort to build a simple and safe language, the Java team did not include some of the C features in Java.

• Java does not include the c unique statement keywords sizeof and typedef.
• Java does not contain the data types struct and union.
• Java does support an Explicit pointer type.
• Java does not define the type modifiers keywords auto, extern, register, signed and unsigned.
• Java does not not have a preprocessor and therefore we can not use # define,

# include, #ifdef.

• Java requires function with no arguments and must be declared with no parenthesis and not with the void keywords as done in C.
• Java adds new operator such as instanceof and >>>.
• Java adds labeled break and continue statements.
• Java adds many features required for object oriented programming.

Java and C++

Java is true object oriented language while C++ is basically C with object oriented extension. That is why the increment operator ++ indicates. C++ has maintained backward compatibility with C. It is therefore possible to write old style C program and Compile and run it under C++. Java appears similar to C++ when we consider only “extension part” of C++. However some object oriented features of C++ make the C++ code extremely difficult to follow and maintain. Following are features are omitted from Java Technology.

• Java does not support operator overloading.
• Java does not have template classes as in C++.
• Java does not support multiple inheritance of classes. This is accomplished using a new feature called “inheritance”.
• Java does not support global variables. Every variable and method is declared with in a class and forms part of that class.
• Java does not use pointers
• Java has replaced the destructor function with a finalize() function.
• There are no header files in Java.

Java also adds some new features. While C++ is superset of C, Java is neither a superset nor a subset of C or C++. Beside this Java adds its own new features. They are as follows.

• Java supports Multithreading.
• Java supports automatic Garbage collection and make lot of programming problems simply vanish.
• The destructor function is replaced with a finalize function.
• Exception handling in Java is different because there is no Destructor. A finally clause is always executed to perform necessary cleanup.
• Java has built –in support for comment documentation, so the source code file can also contain its own documentation.