What is Java ?

  • Java is an object oriented programming language as well as a platform.
  • It was developed by James Gosling in 1995 at Sun Microsystems now Oracle.
  • It is a platform independent programming language.
  • The cross-platform compatibility is also known as “Write Once, Run Anywhere (WORA)”

What is bytecode in Java?

  • Bytecode is a highly optimized set of machine code used by JVM (Java Virtual Machine).
  • It is created by the Java compiler during compilation in the form of a (. class file) with the help of which platform independence feature is achieved.

What is JVM (Java Virtual Machine) ?

  1. Load Codes
  2. Verifies Codes
  3. Executes Codes
  4. Provides run time environment
  • JVM stands for Java Virtual Machine.
  • It is an abstract machine also known as Java Interpreter.
  • It is a specification that provides run time environment in which a java bytecode can be executed. Java Virtual Machine performs the following main tasks:

What is JRE (Java Runtime Environment) ?

  • JRE acronym for Java Runtime Environment
  • JRE is an implementation of JVM
  • It is a set of software tools used for developing Java applications.
  • It contains a set of libraries and other files used by JVM at runtime.

What is JDK (Java Development Kit) ?

  • JDK stands for Java Development Kit
  • JDK is a development kit which provides environment to develop java applications and applets.
  • It contains JRE + JVM + other development tools.
  • It is only used by java developers.

What are the features of a Java language ?

  • It is an object oriented programming language.
  • It is platform independent
  • It is case sensitive language.
  • It is portable in nature.
  • It is open source.
  • It supports multi-threading.
  • It is architecture neutral.
  • It is secure.
  • It has features of exception handling.
  • It supports high performance.

What are Comments ?

  • Comments in java are non-executable statements.
  • It is used to increase the readability of the program.
  • It provides additional information about the program by the programmer, for programmers future use.
  • Comments are basically of 3 types.
    1. Single-line comments: Single-line comments is used for a single line preceded with (//) symbol before the beginning of the statement. It also known as End of line comments. Example: // This is an example of single line comment
    2. Multi-line comments: Multi-line comments is used for multiple line where (/*) symbol is preceded before the beginning of the text and ends with (*/) symbol . It is also known as block comments. It is also known as block comments. Example:/* This is an example of multi line comments. Developed by Vikash Kumar at Java2successc.com */
    3. Documentation comments: Documentation comments is used for a large code of programming bundle. It is used to produce a HTML file that documents the program with the help of javadoc utility. It is preceded with (/**) symbol before the beginning of the first statement and ends with (*/) symbol. Example: /**
      * Method to find average
      * @param numA- This is the first parameter to calculateSum method
      * @param numB – This is the second parameter to calculateSum method