Keywords in Java are reserved words with special meanings and functions. They can’t be used as variable names, method names, or identifiers. Understanding these keywords is essential for writing clear and error-free Java programs.
Keywords in Java
What are Keywords in Java?
- Keywords are the special words whose task is already defined. We can’t change the task of the keyboard. In Java, all keywords are in lowercase.
- Think about traffic signs on the road, Every driver needs to know that a red light means stop and a green light means go. These are universal signals that everyone understands.
- Java keywords work the same way they are special words that tell Java exactly what to do in your program. These words have predefined meanings and are used to perform specific operations or define certain characteristics of the code.
- You can’t use Java keywords for anything other than their intended purpose. They are the basic building blocks that help you create your programs.
Why keywords are important?
- Imagine trying to build a LEGO (Colorful building block toys) set without the instruction manual.
- You might eventually figure it out, but it would be much harder! Java keywords are like the instructions in your manual they tell Java how to build your program.
- When you write a program, you are using these keywords to give Java-specific instructions about what you want it to do.
Characteristics of keywords
- Predefined and Reserved:
- keywords are reserved by the language, and cannot be redefined.
- Case sensitive:
- keywords in Java or case-sensitive. In Java, all keywords are in lowercase. For example, class is a keyword, but Class is not.
- Cannot be used as Identifiers:
- keywords cannot be used as variables, methods, or Class Names.
Examples of keywords in action
Example 1:
Using class, public, and static.
public class Hello {
public static void main(String[] args) {
System.out.println("Hello, World!");
}
}Here,
- class: Defines a class named Hello
- public: Specifies that the method main can be accessed from anywhere.
- static: Indicates that the method belongs to the class rather than an instance of the class.
Note: Here void is also a keyword.
List of Keywords in Java
There are 50+ Keywords in Java Here is the list below.
| Keyword | Description |
| abstract | Declares a class or method as abstract. Abstract classes can’t be directly instantiated, and methods must be implemented by subclasses. Think of it as a blueprint for others to complete. |
| assert | Used during debugging to test conditions at runtime. If the condition is false, it throws an error. |
| boolean | Represents a true or false value. Often used for decisions like “Is this condition met?” |
| break | Exits a loop or a switch statement early. Handy when you’ve found what you’re looking for and want to stop. |
| byte | A small integer data type that holds 8-bit values. Great for saving memory when dealing with lots of small numbers. |
| case | Defines a branch in a switch statement. It’s like giving specific instructions for specific situations. |
| catch | Used to handle exceptions that occur in a try block. It’s like catching and handling errors gracefully. |
| char | Represents a single 16-bit Unicode character. Think of it as a single letter or symbol. |
| class | Used to define a class, which is a blueprint for creating objects in Java. |
| const | Reserved but not used in Java. It’s like a placeholder for something that never got implemented. |
| continue | Skips the current iteration of a loop and moves to the next one. Ideal for skipping unnecessary steps. |
| default | Specifies what happens when no cases match in a switch statement. Think of it as a fallback option. |
| do | Runs a block of code at least once before checking the condition in a do-while loop. |
| double | Represents a 64-bit decimal number. Use it for more precise calculations than float. |
| else | Defines what happens when the if condition is false. Think of it as a backup plan for your logic. |
| enum | Defines a fixed set of named constants, like days of the week. It makes code more readable and safer. |
| extends | Indicates inheritance, meaning one class is taking properties and methods from another. |
| final | Declares constants, prevents method overriding, or stops a class from being inherited. |
| finally | Runs code after a try-catch block, regardless of whether an exception occurred. |
| float | Represents a 32-bit decimal number. Great for saving memory when precision isn’t critical. |
| for | Creates a loop that repeats a block of code for a specific number of times. |
| goto | Reserved but not used in Java. It’s like an old feature that’s left untouched. |
| if | Defines a condition. If it’s true, the block of code inside runs. |
| implements | Indicates that a class is implementing an interface, which is like fulfilling a contract. |
| import | Includes other classes or packages in your program. It’s like saying, “I need tools from this library.” |
| instanceof | Tests if an object is an instance of a specific class or subclass. |
| int | Represents a 32-bit integer. Perfect for whole numbers like 1, 2, or 1000. |
| interface | Declares a contract with methods that must be implemented by classes. Think of it as a “must-do” list. |
| long | Represents a 64-bit integer. Use it when your numbers are too big for int. |
| native | Indicates that a method is implemented in native code using JNI (Java Native Interface). |
| new | Creates new objects or arrays. Think of it as a factory for building things in your program. |
| package | Groups related classes and interfaces together. It’s like organizing files in folders. |
| private | Limits access to members so they can only be used within their own class. It’s like locking a door. |
| protected | Allows access within the same package and by subclasses. It’s a middle ground between public and private. |
| public | Allows members to be accessed from anywhere. It’s like giving everyone full access. |
| return | Exits a method and optionally sends back a value. It’s like completing a task and handing over the result. |
| short | Represents a 16-bit integer. Good for saving memory when working with smaller numbers. |
| static | Associates a member with the class rather than its instances. It belongs to the class itself. |
| strictfp | Ensures consistent floating-point calculations across platforms. |
| super | Refers to the parent class of the current object. Think of it as a way to call for backup from the parent. |
| switch | Implements multi-way branching based on a variable’s value. |
| synchronized | Ensures thread safety by allowing only one thread to access a block or method at a time. |
| this | Refers to the current object instance. It’s like pointing to yourself in a conversation. |
| throw | Explicitly throws an exception in a program. Think of it as raising your hand to signal an error. |
| throws | Declares the exceptions that a method can throw. |
| transient | Prevents serialization of a variable. It’s like marking something as “don’t save this.” |
| try | Starts a block of code to test for exceptions. |
| void | Specifies that a method does not return any value. |
| volatile | Ensures that changes to a variable are visible to all threads. |
| while | Creates a loop that runs as long as the condition is true. |
Summary
- Java keywords are the foundation of the programming language.
- They provide the necessary structure and functionality to build programs. understanding keywords and their purposes ensures that you write an error-free and efficient course.
- Familiarize yourself with these reserved words as the essential for mastering Java programming.
Must Read
Structure of Java Program – Java Syntax – Learn how to structure a Java program with proper syntax.
JVM vs JRE vs JDK – Understand the differences between these essential Java components.
Execution of Java Program – Explore the process of compiling and running Java code.
Variables in Java – Learn how to declare and use variables effectively in Java programs.
Data Types in Java – A guide to different data types available in Java.
FAQ’S
What are keywords in Java?
Keywords are reserved words in Java that have predefined meanings and cannot be used as identifiers like variable names, class names, or method names.
How many keywords are there in Java?
Java has 50 keywords that serve specific purposes in programming.
Can Keywords in Java be used as variable names?
No, keywords cannot be used as variable names because they are reserved for specific functions in the language.
Are Keywords in Java case-sensitive?
Yes, Keywords in Java are case-sensitive. For example, if is a keyword, but If is not.
What is the purpose of the class keyword?
The class keyword is used to define a class in Java, which serves as a blueprint for creating objects.
What does the if keyword do in Java?
The if keyword is used to create conditional statements that execute a block of code when a specified condition is true.
Example:
if (x > 10) {
System.out.println("x is greater than 10");
}
What is the role of the return keyword?
The return keyword is used to exit a method and optionally send back a value to the calling method.
Example:
int add(int a, int b) {
return a + b;
}