Keyword:

• Keywords are predefined identifiers available directly throughout the JVM.
• They have a special meaning inside java source code and outside of comments and strings.
• For Example : public, static, void

Rules:

• Keywords can not be used as user defined identifier by the programmer either for variable or method or class names, because keywords are reserved for their intended use.
• All characters in keyword must be used in lower case.

Need of keywords:

• Basically keywords are used to communicate with compiler and JVM about the operation we perform in java application.
• In java we perform 10 different operations using keywords
• They are:

1. Creating Java file
2. Storing data temporary
3. Creating memory locations
4. Controlling calculations
5. Setting accessibility permissions
6. Modifying default properties
7. Object representation
8. Establishing relations between classes
9. Grouping classes
10. Handling user mistakes

• In java we have 50 keywords to perform all above 10 operations
• Among them 47 introduced in java 1.0
• In Java 1.2 new keyword "strictfp" was added.
• In Java 1.4 new keyword "assert" was added
• In Java 5 new keyword "enum" was added

• Among 50 keywords 2 keywords are reserved words they can not be used in java program, because they defined but they are not implemented , those two are,

1. goto
2. const

1.Java Files

2.Data Types

3.Memory Location

4.Control Statements

1.conditional

2.loop

3.transfer

5.Accessibility Modifiers

6.Modifiers

7.Object Representation

8.Inheritance Relationship

9.Package

10.Exception Handling

11.Unused keywords

Default literals: