Java Keywords Explained – Beginner-Friendly Guide
Introduction: What Are Java Keywords?
When you start learning Java, you will see many special words that look like English words but have fixed meanings in Java.
These special words are called Java Keywords.
Understanding Java keywords is important because:
They form the building blocks of Java programs
You cannot write Java code without them
Using them incorrectly causes errors
What Are Java Keywords?
Java keywords are reserved words that have a predefined meaning in the Java language.
In simple terms:
Java keywords are words that Java understands as commands.
You cannot use keywords as:
Variable names
Class names
Method names
Why Java Keywords Are Important
Java keywords help:
Define the structure of a program
Control the flow of execution
Specify data types and access rules
Without keywords, Java would not understand what your program is supposed to do.
Key Characteristics of Java Keywords
All keywords are written in lowercase
They have fixed meanings
They are reserved by the Java language
You cannot change or redefine them
Categories of Java Keywords
To make learning easier, Java keywords can be grouped into categories.
1. Access Modifiers
These keywords define who can access a class, method, or variable.
| Keyword | Meaning |
|---|---|
| public | Accessible everywhere |
| private | Accessible only within the class |
| protected | Accessible within package or subclass |
Example:
public class Student {
}2. Data Type Keywords
These keywords define the type of data a variable can store.
| Keyword | Description |
|---|---|
| int | Stores whole numbers |
| float | Stores decimal numbers |
| double | Stores large decimal numbers |
| char | Stores a single character |
| boolean | Stores true or false |
Example:
int age = 20;3. Class and Object Keywords
These keywords help create classes and objects.
| Keyword | Purpose |
|---|---|
| class | Defines a class |
| new | Creates an object |
| this | Refers to current object |
Example:
class Car {
}4. Method-Related Keywords
These keywords are used while defining methods.
| Keyword | Meaning |
|---|---|
| void | Returns no value |
| return | Sends value back |
| static | Belongs to class |
Example:
static void display() {
}
5. Control Flow Keywords
These keywords control decision-making and looping.
| Keyword | Purpose |
|---|---|
| if | Executes code if condition is true |
| else | Executes alternative code |
| switch | Multiple condition selection |
| for | Loop with counter |
| while | Loop with condition |
| break | Stops loop |
| continue | Skips current iteration |
6. Inheritance and Polymorphism Keywords
These keywords support object-oriented programming.
| Keyword | Meaning |
|---|---|
| extends | Inherits a class |
| implements | Implements interface |
| super | Refers to parent class |
7. Exception Handling Keywords
These keywords handle runtime errors.
| Keyword | Purpose |
|---|---|
| try | Wraps risky code |
| catch | Handles exception |
| finally | Always executes |
| throw | Throws exception |
| throws | Declares exception |
8. Other Common Java Keywords
| Keyword | Description |
|---|---|
| final | Prevents change |
| abstract | Incomplete class or method |
| interface | Blueprint of class |
| package | Groups classes |
| import | Access other packages |
| null | No object reference |
| instanceof | Checks object type |
Real-Life Analogy
Think of Java keywords like traffic signals:
Red → Stop (
break)Green → Go (
continue)Direction signs → Control flow (
if,else)
You must follow them exactly, or traffic (program) fails.
Frequently Asked Questions (FAQs)
Q1. How many keywords are there in Java?
Java has around 50+ reserved keywords.
Q2. Can Java keywords be used as variable names?
No. Keywords are reserved and cannot be used as identifiers.
Q3. Are Java keywords case-sensitive?
Yes. Java keywords must be written in lowercase.
Q4. Is main a Java keyword?
No. main is a method name, not a keyword.
Q5. Is String a keyword in Java?
No. String is a class, not a keyword.