Java Keywords All List With Descriptions

Java Keywords All List With Descriptions 

Java Language Keywords

Java Keywords List: In the Java artificial language, a Keyword is anyone of fifty-two reserved words that have a predefined that means within the language attributable to this, programmers cannot use keywords as names for variables, methods, classes, or as the other symbol.

Java Language Keywords: Java keywords in the Java programming language. You cannot use any of the following as identifiers in your programs. The keywords const and goto are reserved, even though they are not currently used. true, false, and null might seem like keywords, but they are actually literals; you cannot use them as identifiers in your programs.

Java Keywords List

1. abstract 2. boolean       3. break         4. byte 5. case     6. catch            7. char             8. class 9. continue  10. default  11. do    12. double 13. else          14. enum  15. extends 16. final 17. finally       18. float          19. for       20. if 21. implements 22. import 23. instanceof 24. int 25. interface      26. long      27. new        28. package 29. private   30. protected    31. public  32. return 33. short       34. static         35. super    36. switch 37. this           38. throw       39. throws      40. try 41. void 42. while

Java Keywords List and Descriptions

Abstract: An abstract class cannot be used to create objects (to access it, it must be inherited from another class). An abstract method can only be used in an abstract class, and it does not have a body. The body is provided by the 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 store whole numbers from -128 and 127 Case: Marks a block of code in switch statements Catch: Catches exceptions generated by try statements Char: A data type that is used to store a single character Class: Defines a class Continue: Continues to the next iteration of a loop Const: Defines a constant. Not in use - use final instead Default: Specifies the default block of code in a switch statement Do: Used together with while to create a do-while loop Double: A data type that can store whole numbers from 1.7e−308 to 1.7e+308 Else: Used in conditional statements Enum: Declares an enumerated (unchangeable) type Exports: Exports a package with a module. New in Java 9 Extends: Extends a class (indicates that a class is inherited from another class) Final: A non-access modifier used for classes, attributes, and methods, which makes them non-changeable (impossible to inherit or override) Finally: Used with exceptions, a block of code that will be executed no matter if there is an exception or not Float: A data type that can store whole numbers from 3.4e−038 to 3.4e+038 For: Create a for loop Goto: Not in use, and has no function If: Makes a conditional statement Implements: Implements an interface Import: Used to import a package, class, or interface Instanceof: Checks whether an object is an instance of a specific class or an interface Int: A data type that can store whole numbers from -2147483648 to 2147483647 Interface: Used to declare a special type of class that only contains abstract methods Long: A data type that can store whole numbers from -9223372036854775808 to 9223372036854775808 Module: Declares a module. New in Java 9 Native: Specifies that a method is not implemented in the same Java source file (but in another language) 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-access 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

Java Language Rules for Naming an Identifier

1. Identifiers cannot be a keyword.

2. Identifiers are case-sensitive.

3. It can have a sequence of letters and digits. However, it must begin with a letter, $ or _. The first letter of an identifier cannot be a digit.

4. It's a convention to start an identifier with a letter rather than $ or _.

5. Whitespaces are not allowed.

6. Similarly, you cannot use symbols such as @, #, and so on.

Java Language same valid identifiers

1. score

2. level

3. highest score

4. number1

5. convertToString

Java Language same invalid identifiers

1. class

2. float

3. 1number

4. highest Score

5. @pple

Java Keywords List and Descriptions with Examples

1. abstract: Using the abstract keyword in java we can create abstract classes and methods. Abstract keywords are essential to implement abstraction into a program.

abstract class DataFlair

     

2. assert: Using the assert keyword we can implement assertion in a program. Using it we can check the correctness of any assumptions made in a program. The assert keyword was added in JDK 1.4.

int i = 10;            assert I> 5: "The value is greater than 5";

3. boolean: Using the boolean keyword we can declare a boolean variable. A boolean variable is a variable that has two values, true and false.

boolean flag=true;

 

4. break: The break keyword is a jump statement using which we can break out of a loop or switch statement. The break statement terminates the currently executing block of code.

i=0; while(true) {      if(i==10)      break;      i++; }

 

5. byte: Using the byte keyword in java we can declare a variable that can hold a value of 1 byte or 8 bit.

byte num=1;

 

6. case: Using the case statement we can declare each case inside a switch-case block.

{      case 1:                System. out.println(“ONE”);                break; }

 

7. catch: The catch keyword is part of exception handling in java. Using the catch keyword we can catch or capture the error caught by the try block. A catch block can exist only after the try block.

catch (Exception e) {        System. out.println(“An exception was caught by the try block”); }

 

8. char: Using the char keyword we can declare a character variable.

char ch= 'A';

 

9. class: Using the class keyword we can declare a class in java.

class DataFlair

 

10. continue: Continue is also a jump statement in java. Using it we can terminate the current iteration and continue from the next iteration inside the loop.

i=0; while(i<=10) {      if(i==5)      continue;      i++; }

11. default: default is the keyword using which we can declare the default statement inside a switch case. It is executed when none of the cases match.

Switch(num) {      case 1:                System. out.println(“ONE”);                break;      default:                System. out.println(“Not ONE”); }

12. do: Using the do keyword we can declare a do-while loop. It is an exit-controlled loop, so it doesn’t have any entry conditions.

i=0; do{         i++;      }while(i<=10);

 

13. double: Using the double keyword we can declare a double variable. A double variable can hold a 64bit long floating point number.

double d=1.23456

14. else: Using the else keyword we can write statements that will be executed when the if block doesn’t execute successfully.

i=5; if(i!=5) System. out.println(“Not Five”); else System. out.println(“FIVE”);

15. enum: Using the enum keyword we can declare an enumerated class. It consists of a fixed set of constants. Enum constructors are always private by default. Enum keyword was added to java in JDK 5.0.

enum Rainbow {   Violet, Indigo, Blue, Green,   Yellow, Orange, Red; }

16. extends: extend keyword is used in inheritance. Using it we can inherit one class into another.

class subclass extends superclass

17. final: Using the final keyword we can finalize the value of a variable. It means that the value cannot be updated by the user whatsoever.

final int num=1000

18. finally: The final keyword is used after the try-catch block. It indicates the end of the block. Unlike the try-catch block, the final block will be executed regardless of whether an exception is found or not.

finally{ System. out.println("This block is always executed whatsoever!"); }

19. float: Using the float keyword we can declare a float variable in java. The float variable holds a 32-bit long floating-point number.

float num= 1.324f;

20. for: Using the for the keyword we can declare a for a loop. It is an entry-controlled loop, for this kind of loop the number of iterations should be known beforehand.

for(i=0;i<10;i++) {     System.out.println(i); }

21. if: In java, the if keyword is used to declare an if conditional statement. The if statement is used to check the viability of a condition.

i=5; if(i==5) {     System. out.println(“The Number is Five”); }

22. implements: Using the implements keyword in java we can declare an interface. It is like the inheritances extend keyword, here to access an interface we have to use the implements keyword.

interface DataFlair{ public void intern(); } class internship implements DataFlair {         Public void intern()        {                 System.out.println(“Internship Granted”);         } }

23. import: Using the import keyword in java we can access classes and interfaces present inside a package to the current code.

import java.util.Arrays;

24. instanceof: Using the instanceof keyword in java we can check whether a given object is an instance of another class or not. It returns true if the given object is an instance and false if not.

public class DataFlair {   public static void main(String[] args) {     DataFlair Obj1 = new DataFlair();     System.out.println(Obj1 instanceof DataFlair);// It will return True.   } }

25. int: Using the int keyword we can declare a variable of integer datatype. It can hold a value of 32-bit long.

int num=100;

26. interface: Using the interface keyword in java we can declare an interface inside the code.

interface DataFlair{}

27. long: Using the long keyword we can declare variables with the long data type. The long data type is an integer that can hold 64-bit data.

long num=10000;

28. native: The native keyword in java is used to indicate that a method is implemented in native code using JNI[Java Native Interface].

Public native void Dataflair()

29. new: Using the new keyword we can create a new instance for a class.

public class Dataflair(){ public static void main(String[] args){ DataFlair obj1=new DataFlair(); }

30. Package: Using the package keyword in java we can create a new package in the java library.

package com.DataFlair.Keywords;

31. private: private keyword is an access modifier that declares a class or method as private; i.e; it can only be accessed by its local variables.

private class DataFlair{}

32. protected: protected is also an access modifier that declares a class or method as protected; i.e; it can be accessed by files in the PWD(Present Working Directory).

protected class DataFlair{}

33. public: the public is another access modifier that declares a class or method as public; i,e; it can be accessed globally.

public class DataFlair{}

34. return: The return keyword is used inside a method when it requires to return of a value of a certain return type except for the void.

int sum(int a, int b) {      return (a+b); }

35. short: In java, the short keyword declares variables that can hold an integer value of 16-bit long.

short num=1;

36. static: In java, the static keyword declares a static variable or method. A static variable or method is stored in a static memory location.

public static void main()

37. strictfp: In java, the strictfp keyword ensures that every platform gets the same result for floating-point operation. The strictfp keyword is used on classes, methods, and interfaces. This keyword was introduced in JDK 1.2.

strictfp class DataFlair{}

38. super: The super keyword distinguishes variables with the same name in both parent class and child class in inheritance.

class DataFlair {      String name=” Company”; } class internship extends DataFlair/ {      String name=” Intern”;      System.out.println(name);//Intern will be printed      System.out.println(super.name);//Company will be printed }

39. switch: Using the switch keyword we can initiate the switch case block in a java code.

Switch(num) {      case 1:                System. out.println(“ONE”);                break;      default:                System. out.println(“Not ONE”); }

40. synchronized: Using the synchronized keyword in java we can specify the critical section to be executed during multithread coding

synchronized void print(int num)

41. this: this keyword in java is used to distinguish local variables from global variables.

class DataFlair{ String name; DataFlair(String name) {      this.name=name; } }

42. throw: The throw keyword in java is used to throw custom-made exceptions explicitly into the code.

throw new IOException("The Input is Not Acceptable”);

43. throws: The throws keyword is used to propagate a checked exception.

import java.io.*;  class DataFlair{   void internship()throws IOException{    throw new IOException("Internship Not Found");   }  }

44. transient: Using the transient keyword in java we can deserialize a variable. When a variable is declared transient, it is not considered for serialization.

transient int num;}

45. try: The try block is used in exception handling to test a block of code for exceptions. The try block is always followed by a catch block or finally block.

try{ //statement }catch(exception e){}

46. void: Using the void keyword we can declare that the method will not return any value.

void main()

47. volatile: volatile keyword in java is used to indicate that a variable can change asynchronously.

static volatile int num=100;

48. while: Using the While keyword we can declare a while loop. While loop is an entry-controlled loop, where the number of iterations is not fixed.

i=5; while(i<=10) {     i++; }

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