The Java programming language has 50 keywords. Each keyword has a specific meaning in the language. You can't use a keyword for anything other than its pre-assigned meaning.
The following table lists Java's keywords.
| Keyword | What It Does |
abstract |
Indicates that the details of a class, a method, or an interface are given elsewhere in the code. |
assert |
Tests the truth of a condition that the programmer believes is true. |
boolean |
Indicates that a value is either true or false. |
break |
Jumps out of a loop or switch. |
byte |
Indicates that a value is an 8-bit whole number. |
case |
Introduces one of several possible paths of execution in a switch statement. |
catch |
Introduces statements that are executed when something interrupts the flow of execution in a try clause. |
char |
Indicates that a value is a character (a single letter, digit, punctuation symbol, and so on) stored in 16 bits of memory. |
class |
Introduces a class — a blueprint for an object. |
const |
You can't use this word in a Java program. The word has no meaning but, because it's a keyword, you can't create a variable named const. |
continue |
Forces the abrupt end of the current loop iteration and begins another iteration. |
default |
Introduces a path of execution to take when no case is a match in a switch statement. |
do |
Causes the computer to repeat some statements over and over again (for instance, as long as the computer keeps getting unacceptable results). |
double |
Indicates that a value is a 64-bit number with one or more digits after the decimal point. |
else |
Introduces statements that are executed when the condition in an if statement isn't true. |
enum |
Creates a newly defined type — a group of values that a variable can have. |
extends |
Creates a subclass — a class that reuses functionality from a previously defined class. |
final |
Indicates that a variable's value cannot be changed, that a class's functionality cannot be extended, or that a method cannot be overridden. |
finally |
Introduces the last will and testament of the statements in a try clause. |
float |
Indicates that a value is a 32-bit number with one or more digits after the decimal point. |
for |
Gets the computer to repeat some statements over and over again (for instance, a certain number of times). |
goto |
You can't use this word in a Java program. The word has no meaning. Because it's a keyword, you can't create a variable named goto. |
if |
Tests to see whether a condition is true. If it's true, the computer executes certain statements; otherwise, the computer executes other statements. |
implements |
Indicates that a class provides bodies for methods whose headers are declared in an interface. |
import |
Enables the programmer to abbreviate the names of classes defined in a package. |
instanceof |
Tests to see whether a certain object comes from a certain class. |
int |
Indicates that a value is a 32-bit whole number. |
interface |
Introduces an interface. An interface is like a class but, for the most part, an interface's methods have no bodies. |
long |
Indicates that a value is a 64-bit whole number. |
native |
Enables the programmer to use code that was written in a language other than Java. |
new |
Creates an object from an existing class. |
package |
Puts the code into a package — a collection of logically related definitions. |
private |
Indicates that a variable or method can be used only within a certain class. |
protected |
Indicates that a variable or method can be used in subclasses from another package. |
public |
Indicates that a variable, class, or method can be used by any other Java code. |
return |
Ends execution of a method and possibly returns a value to the calling code. |
short |
Indicates that a value is a 16-bit whole number. |
static |
Indicates that a variable or method belongs to a class, rather than to any object created from the class. |
strictfp |
Limits the computer's ability to represent extra large or extra small numbers when the computer does intermediate calculations on float and double values. |
super |
Refers to the superclass of the code in which the word super appears. |
switch |
Tells the computer to follow one of many possible paths of execution (one of many possible cases), depending on the value of an expression. |
synchronized |
Keeps two threads from interfering with one another. |
this |
A self-reference — refers to the object in which the word this appears. |
throw |
Creates a new exception object and indicates that an exceptional situation (usually something unwanted) has occurred. |
throws |
Indicates that a method or constructor may pass the buck when an exception is thrown. |
transient |
Indicates that, if and when an object is serialized, a variable's value doesn't need to be stored. |
try |
Introduces statements that are watched (during runtime) for things that can go wrong. |
void |
Indicates that a method doesn't return a value. |
volatile |
Imposes strict rules on the use of a variable by more than one thread at a time. |
while |
Repeats some statements over and over again (as long as a condition is still true). |
