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List of all Java Keywords

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  • Difficulty Level : Easy
  • Last Updated : 09 Mar, 2022

Keywords or Reserved words are the words in a language that are used for some internal process or represent some predefined actions. These words are therefore not allowed to use as variable names or objects. If we do we will get a compile-time error as shown below as follows:

Illustration:

Java




// Java Program to Illustrate What If We use the keywords as the variable name
// Code Contributed by @Shubham Jain
 
class HelloWorld {
    public static void main(String[] args)
    {
 
        int this = "Hello World!"; // Note "this" is a reserved word in java
        System.out.println(this);
    }
 }


Output:

Errors in Code : Compiler Error

prog.java:11: error: not a statement
        int this = "Hello World!"; // Note "this" is a reserved word in java
        ^
prog.java:11: error: ';' expected
        int this = "Hello World!"; // Note "this" is a reserved word in java
           ^
2 errors

Java contains a list of keywords or reserved words which are also highlighted with different colors be it an IDE or editor in order to segregate the differences between flexible words and reserved words. They are listed below in the table with the primary action associated with them.
 

S.No Keyword Usage
1. abstract Specifies that a class or method will be implemented later, in a subclass 
2. assert Assert describes a predicate placed in a java program to indicate that the developer thinks that the predicate is always true at that place.
3.  boolean A data type that can hold True and False values only 
4. break A control statement for breaking out of loops.
5. byte A data type that can hold 8-bit data values 
6. case Used in switch statements to mark blocks of text
7. catch Catches exceptions generated by try statements
8. char  A data type that can hold unsigned 16-bit Unicode characters
9. class Declares a new class
10. continue Sends control back outside a loop 
11. default Specifies the default block of code in a switch statement
12. do Starts a do-while loop
13. double A data type that can hold 64-bit floating-point numbers
14. else Indicates alternative branches in an if statement 
15. enum A Java keyword is used to declare an enumerated type. Enumerations extend the base class.
16. extends Indicates that a class is derived from another class or interface 
17. final Indicates that a variable holds a constant value or that a method will not be overridden
18. finally Indicates a block of code in a try-catch structure that will always be executed
19. float A data type that holds a 32-bit floating-point number 
20. for Used to start a for loop
21. if Tests a true/false expression and branches accordingly
22. implements Specifies that a class implements an interface 
23. import  References other classes
24. instanceof Indicates whether an object is an instance of a specific class or implements an interface 
25. int A data type that can hold a 32-bit signed integer 
26. interface Declares an interface
27. long A data type that holds a 64-bit integer
28. native Specifies that a method is implemented with native (platform-specific) code 
29. new Creates new objects 
30. null This indicates that a reference does not refer to anything 
31. package Declares a Java package
32. private An access specifier indicating that a method or variable may be accessed only in the class it’s declared in
33. protected An access specifier indicating that a method or variable may only be accessed in the class it’s declared in (or a subclass of the class it’s declared in or other classes in the same package)
34. public An access specifier used for classes, interfaces, methods, and variables indicating that an item is accessible throughout the application (or where the class that defines it is accessible)
35. return Sends control and possibly a return value back from a called method 
36. short A data type that can hold a 16-bit integer 
37 static Indicates that a variable or method is a class method (rather than being limited to one particular object)
38. strictfp A Java keyword is used to restrict the precision and rounding of floating-point calculations to ensure portability.
39. super Refers to a class’s base class (used in a method or class constructor) 
40. switch A statement that executes code based on a test value 
41. synchronized Specifies critical sections or methods in multithreaded code
42. this Refers to the current object in a method or constructor 
43. throw  Creates an exception 
44. throws Indicates what exceptions may be thrown by a method 
45. transient Specifies that a variable is not part of an object’s persistent state
46. try Starts a block of code that will be tested for exceptions 
47. void Specifies that a method does not have a return value
48. volatile This indicates that a variable may change asynchronously
49. while Starts a while loop

Note: 

  • The keywords const and goto are reserved, even they are not currently in use.
  • Currently they are no longer supported in Java.
const Reserved for future use
goto Reserved for future use


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