Java Keywords

Java has keywords which are the words that act like keys for the code. However, please note those cannot be used as variable or class or object names. Those are the special words that need to start with lowercase letters. We have already learnt some of them, such as; class, void, int, … etc. And you can see the rest of them in the following table.

Keyword	Description
abstract	Specifies that a class or method will be implemented later, in a subclass
assert	For debugging
boolean	A data type that can only store true and false values
break	Breaks out of a loop or a switch block
byte	A data type that can hold 8-bit data values
case	Marks a block of code in switch statement
catch	Catches exceptions generated by try statements
char	A data type that is used to store a single character
class	Defines a class
continue	Sends control back outside a loop
default	Specifies the default block of code in a switch statement
do	Starts a do-while loop
double	A data type that can hold 64-bit floating-point numbers
else	Indicates alternative branches in an if statement
enum	Declares an enumerated (unchangeable) type and extend the base class
exports	Exports a package with a module. New in Java 9
extends	Indicates that a class is derived from another class or interface
final	Indicates that a variable holds a constant value or that a method will not be overridden
finally	Indicates a block of code in a try-catch structure that will always be executed
float	A data type that holds a 32-bit floating-point number
for	Create a for loop
if	Makes a conditional statement
implements	Implements an interface
import	Used to import a package, class or interface
instanceof	Indicates whether an object is an instance of a specific class or implements an interface
int	A data type that can hold a 32-bit signed integer
interface	Declares an interface
long	A data type that holds a 64-bit integer
module	Declares a module. New in Java 9
native	Specifies that a method is implemented with native (platform-specific) code
new	Creates new objects
package	Declares a package
private	An access modifier used for attributes, methods and constructors, making them only accessible within the declared class
protected	An access modifier used for attributes, methods and constructors, making them accessible in the same package and subclasses
public	An access modifier used for classes, attributes, methods and constructors, making them accessible by any other class
requires	Specifies required libraries inside a module. New in Java 9
return	Finished the execution of a method, and can be used to return a value from a method
short	A data type that can store whole numbers from -32768 to 32767
static	A non-access modifier used for methods and attributes. Static methods/attributes can be accessed without creating an object of a class
strictfp	Restrict the precision and rounding of floating point calculations
super	Refers to superclass (parent) objects
switch	Selects one of many code blocks to be executed
synchronized	A non-access modifier, which specifies that methods can only be accessed by one thread at a time
this	Refers to the current object in a method or constructor
throw	Creates a custom error
throws	Indicates what exceptions may be thrown by a method
transient	A non-accesss modifier, which specifies that an attribute is not part of an object’s persistent state
try	Creates a try…catch statement
var	Declares a variable. New in Java 10
void	Specifies that a method should not have a return value
volatile	Indicates that an attribute is not cached thread-locally, and is always read from the “main memory”
while	Creates a while loop

Example:

This is an example for finding the smallest and largest numbers from a given set of numbers. In our example we enter three numbers and the program tells us smallest and largest. You will see that we used multiple keywords; int, do, while, if and else.