Basics of Java Programming: Keywords, Literals, and Identifiers

-

Basics of Java Program

The basics of a Java program include keywords, literals, and identifiers. These are the fundamental building blocks used while writing Java code.

1. Keywords

Keywords are reserved words in Java that have predefined meanings and functionality for the Java compiler.

Key points:

Keywords must be written in lowercase.
Java has 50 reserved keywords.
Out of these, 48 keywords have predefined meaning and functionality.
The remaining 2 reserved words (goto and const) are not used and have no functionality.

Examples of Java keywords:

  • class
  • static
  • final
  • public
  • void

Keywords cannot be used as variable names, method names, or identifiers.

2. Literals

Literals are fixed values that are directly stored in a Java program.

Java supports five types of literals:

Integer Literals:

Eg:- 1, 25, 100

Floating-Point Literals:

Eg:- 1.5, 2.75

Character Literals:

Eg:- 'a', 'Z'

String Literals:

Eg:- "Java", "Programming"

Boolean Literals:

Eg:- true, false

Literals are used to assign values to variables in a Java program.

3. Identifiers

Identifiers are names given to variables, methods, classes, and objects in Java.

Rules for identifiers:

  • The first character must be an alphabet (A–Z or a–z), $, or _.
  • Identifiers cannot start with a number.
  • After the first character, digits can be used.
  • Spaces are not allowed.
  • Keywords cannot be used as identifiers.
  • Operators cannot be used as identifiers.
     🔹 Note on underscore (_):
  • In JDK 1.7 and earlier, _ can be used as an identifier.
  • From JDK 8 onwards, _ alone is not allowed as an identifier.

Examples of valid identifiers:

  • totalAmount
  • $count
  • student1

Examples of invalid identifiers:

  • 1value
  • total amount
  • class

Comments

Post a Comment

Popular posts from this blog

History of Java Programming Language | Features, Origin & Uses

-
History of Java Programming Language  Java is a world famous programming language. It is a high-level, object-oriented programming language developed by Sun Microsystems in the early 1990s. Java's development began in 1991 with the goal of creating applications for embedded devices, setup boxes, microwaves, digital cable systems, and web applications. The language was officially released to the public in 1995. Who Created Java Programming? The Java design was led by James Gosling, along with a small team of engineers known as the Green Team. Their original thing was to produce a programming language for consumer electronic  bias  similar as interactive  TV systems. still, the focus  latterly shifted to  erecting a platform-independent language suitable for general- purpose programming.  Origin and Naming of Java Firstly, Java was named Oak, inspired by an oak tree located outside James Gosling’s office. The name was  latterly changed to Java becau...
Read more

Inheritance in Java: Types, Examples, and Explanation

-
Inheritance in Java Inheritance is one of the core concepts of Object-Oriented Programming (OOP). It allows one class to inherit the state (variables) and behavior (methods) of another class.  In simple words, inheritance promotes code reuse and establishes a parent–child relationship between classes. ✅ Definition Inheritance is a mechanism where one class acquires the properties and methods of another class The class that provides data is called the Superclass (Parent class) The class that receives data is called the Subclass (Child class) In Java, inheritance is implemented using the extends keyword 🌍 Real-Life Example Family Inheritance A child inherits eye color, height, and surname from parents Parents → Superclass Child → Subclass Similarly, a subclass inherits variables and methods from its superclass. 🔹 Syntax of Inheritance class SubClass extends SuperClass {     // subclass members } 🔑 Important Points A subclass consumes the state and behavior of the supercl...
Read more

Java Programming Features Every Beginner Should Know

-
Features of Java Java is a powerful programming language that provides several important features, making it popular for developing secure and reliable applications. 1. Platform Independent Java is called a platform-independent language because a Java program does not depend on a specific operating system. When a Java program is compiled, it generates a .class file. This file contains intermediate bytecode, not machine-specific code. The .class file can run on any operating system as long as the system has JVM (Java Virtual Machine) installed. This concept is known as “Write Once, Run Anywhere.” 2. Java Compiler The Java compiler (javac) is a program that converts the source code written by a developer into bytecode. The compiler: Takes a .java file as input Converts it into intermediate machine code Stores the output in a .class file This bytecode is platform independent and can be executed on any system with JVM support. 3. Java Virtual Machine (JVM) The JVM (Java Virtual Machine) ...
Read more