Keywords in Java

List of Java Keywords

Java, at present, uses 49 reserved words, excluding the goto and const keywords which are currently not in use. The list of keywords used in Java, along with their meaning and implementation are shown below.

Keyword	Description	Implementation and Use
abstract	A non-access modifier that is used on classes and methods to imply that it would be implemented later in the program.	abstract class A {  …   abstract void methodA(); } class B extends A {   @Override   void methodA()   { … } } You can also try this code with Online Java Compiler Run Code
assert	It describes a true-false statement to indicate that the user wants the result to be true.	assert expression1 : expression2; You can also try this code with Online Java Compiler Run Code
boolean	A primitive data type that declares a variable to hold two values - true and false	boolean x = true; You can also try this code with Online Java Compiler Run Code
break	A control statement used to break out of loops and switch case blocks.	while(condition) {   if (condition)     break; } You can also try this code with Online Java Compiler Run Code
byte	It is a signed 8-bit primitive data type in Java. Range: -128 to 127	byte a =1; You can also try this code with Online Java Compiler Run Code
char	A primitive data type that is used to declare a character variable.	char ch = ‘a’; You can also try this code with Online Java Compiler Run Code
case	This is used in switch-case statements to execute blocks of code based on specific events/conditions.	switch(exp) {   case x: …               break;   .   .   default: … } You can also try this code with Online Java Compiler Run Code
catch	It is used to catch the exceptions generated by try statements.	try { … } catch (Exception e) { … } You can also try this code with Online Java Compiler Run Code
class	To define and declare a class in Java.	class Class_name { … } You can also try this code with Online Java Compiler Run Code
continue	A control statement that is used to skip the current iteration and continue to the next.	while(condition) {   if (condition)     continue; } You can also try this code with Online Java Compiler Run Code
default	An access modifier that restricts the access of its members outside the declared package.   It specifies the default block of code in a switch statement.	class A {   default void methodA( ) { } } switch(exp) {   case x: …         break;   default: … } You can also try this code with Online Java Compiler Run Code
do	It is used to start a do-while loop.	do { … } while (condition); You can also try this code with Online Java Compiler Run Code
double	A primitive data type that declares variables to store 64-bit floating point numbers.	double x = 23.46287573734; You can also try this code with Online Java Compiler Run Code
else	It is used to declare an alternate set of codes for an if statement.	if (condition) { … } else { … } You can also try this code with Online Java Compiler Run Code
enum	A keyword used to declare an enumerated data type that represents a group of constants.	enum enum_name {  … ,   constant_n; } You can also try this code with Online Java Compiler Run Code
extends	It is used to indicate that a class is derived from another class.	class A { … } class B extends A { … } You can also try this code with Online Java Compiler Run Code
final	A non-access modifier which indicates that the contents of its variable, class or method is constant and final.	final variable1 = 20; You can also try this code with Online Java Compiler Run Code
finally	It is used with try-catch statements to deal with exceptions. It holds the block of code that is executed irrespective of whether an exception exists or not.	try { … } catch (Exception e) { … } finally { … } You can also try this code with Online Java Compiler Run Code
float	A primitive data type that declares a variable to hold 32-bit floating-point numbers.	float x = 234.34; You can also try this code with Online Java Compiler Run Code
for	It is used to start a for loop.	for ( … ; … ; … ) { … } You can also try this code with Online Java Compiler Run Code
if	It starts an if conditional statement.	if (condition) { … } You can also try this code with Online Java Compiler Run Code
implements	It indicates that the class implements an interface.	interface A {   public void methodA(); } class B implements A {   @Override   void methodA()   { … } } You can also try this code with Online Java Compiler Run Code
import	It is used to import a package or class.	import java.util.*; You can also try this code with Online Java Compiler Run Code
instanceof	It is used to check whether an object is an instance of a specific class or if it implements an interface.	object_name instanceof class_name; You can also try this code with Online Java Compiler Run Code
int	A primitive data type that can hold integers in the range -2147483648 to 2147483647	int x = -3825; You can also try this code with Online Java Compiler Run Code
interface	It is used to declare a class for only abstract methods.	interface Interface_name {  void methodA( ); } You can also try this code with Online Java Compiler Run Code
long	A primitive data type capable of holding very large numbers. (64-bit integers)	long x = 4354748364448; You can also try this code with Online Java Compiler Run Code
native	It is used to indicate that the method is implemented in a language other than Java (native platform-specific code )	public native void method(); You can also try this code with Online Java Compiler Run Code
new	It is used to create new objects of a class or an array.	Class_name obj = new Class_name(); You can also try this code with Online Java Compiler Run Code int[ ] arr = new int[size];   You can also try this code with Online Java Compiler Run Code
package	To declare a new package.	package package_name; You can also try this code with Online Java Compiler Run Code
private	An access modifier that allows access of its members only within the declared class.	private void method() { … } You can also try this code with Online Java Compiler Run Code
protected	An access modifier that allows access of its members within the package and all of its subclasses.	protected void methodA() { … } You can also try this code with Online Java Compiler Run Code
public	An access modifier that allows access of its members to the entire Java universe.	public void methodA() { … } You can also try this code with Online Java Compiler Run Code
return	It causes the control to return from a called method back to the calling method.	public void methodB() {  …   return; } public void methodA() {  …   methodB(); } You can also try this code with Online Java Compiler Run Code
short	A data type that holds 16-bit integers.	short x = 21; You can also try this code with Online Java Compiler Run Code
static	A non-access modifier which indicates that it can be accessed without the creation of an object.	public static void main() { … } You can also try this code with Online Java Compiler Run Code
strictfp	It restricts the precision and truncation of floating-point calculations to ensure portability.	public strictpf class A { … } You can also try this code with Online Java Compiler Run Code
super	It is used to refer to the object of a parent class.	super(argument_list); You can also try this code with Online Java Compiler Run Code
switch	It is used to create a multiway branch statement.	switch(exp) {   case x: …          break;    …   default: … } You can also try this code with Online Java Compiler Run Code
synchronised	A non-access modifier which tells that the critical sections of a multithreaded code should be executed one thread at a time.	public synchronised void methodA() { … } You can also try this code with Online Java Compiler Run Code
this	It is used to reference the current object variable or method. this() can be used to invoke the current class constructor.	class A {   public int a;   public A( int b)   {     this.a = b;   } } You can also try this code with Online Java Compiler Run Code
throw	It is used to throw a declared exception and create a custom error.	throw new exception_type(message); You can also try this code with Online Java Compiler Run Code
throws	throws is used to indicate the exception type that may be thrown by a method.	void methodA() throws exception_type { … } You can also try this code with Online Java Compiler Run Code
transient	A non-access modifier which specifies that an attribute is not part of an object's persistent state.	private transient int variable_name;
try	It is used to start a try-catch block that handles exceptions.	try { … } catch (Exception e) { … } You can also try this code with Online Java Compiler Run Code
void	It is used to declare that a method does not return any value.	public static void main() You can also try this code with Online Java Compiler Run Code
volatile	Volatile specifies that a variable is asynchronously modified by concurrently running threads.	static volatile int var_name = 5; You can also try this code with Online Java Compiler Run Code
while	It is used to start a while loop.	while(condition) { … } You can also try this code with Online Java Compiler Run Code

You can practice on online Java Compiler.

Example of Java Keywords

public class Example {
   public static void main(String[] args) {
       int number = 10; // `int` is a keyword for declaring an integer variable
       final int CONSTANT = 5; // `final` is a keyword to declare a constant
       if (number > CONSTANT) { // `if` is a control-flow keyword
           System.out.println("Number is greater than the constant.");
       } else {
           System.out.println("Number is less than or equal to the constant.");
       }
   }
}

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Output

Number is greater than the constant.

Frequently Asked Questions

How many keywords are there in Java?

Java has 52 reserved keywords as of the latest versions. These are predefined and cannot be used as identifiers like variable or class names.

Is null a keyword in Java?

No, null is a literal, not a keyword in Java. It represents the absence of a value for object references but isn't classified as a reserved keyword.

What are keywords also called in Java?

In Java, keywords are also known as reserved words. They have special meanings and are predefined by the Java language, serving specific purposes within the code structure and control flow.

Can I use Java keywords as variable names?

No, Java keywords cannot be used as variable names because they are reserved by the language for specific functions and commands, ensuring clarity in code syntax and preventing conflicts during compilation.

Differences between 'this' and 'super' keywords in Java:

The this keyword refers to the current instance of a class, allowing access to its members. In contrast, super refers to the superclass instance, enabling access to superclass methods and variables overridden in the subclass.

Conclusion

Keywords are an important part of any program we write. The purpose and behaviour of any variable, class, method or constructor can not be conveyed to the JVM without the help of Keywords. Hence, it is essential to have a deep understanding of them. This blog has covered all the reserved words in Java along with their description and use. We have also discussed implementing them to make your Java program more efficient.

Recommended Readings:

• This and final Keyword
• Why is Java Platform Independent
• Java Tokens
• Java Verify
• Super Keyword In Java
• Exceptions with throw and throws Keywords
• Addition of two numbers in java