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Java Keywords

Java keywords are reserved words with predefined meanings in the Java programming language. Here's a comprehensive list:

Reserved Words:

  • Java keywords cannot be used as identifiers (e.g., variable names, class names).
  • They are reserved for specific purposes within the language.
Java Reserved Keywords

Java Reserved Keywords

Keyword Description
abstract Defines an abstract class or method.
assert Asserts that a condition is true.
boolean Defines a boolean type.
break Terminates a loop or switch statement.
byte Defines a byte type.
case Specifies a value in a switch statement.
catch Catches exceptions generated by try statements.
char Defines a char type.
class Defines a class.
const Defines a constant (not used).
continue Continues to the next iteration of a loop.
default Specifies the default case in a switch statement.
do Starts a do-while loop.
double Defines a double type.
else Specifies the statement to execute if a condition is false.
enum Defines an enumeration (enum) type.
extends Indicates that a class is derived from another class or interface.
final Indicates that a variable or method is final and cannot be changed.
finally Specifies a block of code to execute after a try-catch block.
float Defines a float type.
for Starts a for loop.
goto Reserved keyword (not used).
if Specifies the statement to execute if a condition is true.
implements Indicates that a class implements an interface.
import Imports a package or class.
instanceof Indicates whether an object is an instance of a class or interface.
int Defines an int type.
interface Defines an interface.
long Defines a long type.
native Specifies that a method is implemented in native code.
new Creates a new instance of a class or array.
package Declares a package.
private Specifies that a variable or method is accessible only within its own class.
protected Specifies that a variable or method is accessible within its own package and by subclasses.
public Specifies that a variable or method is accessible from anywhere.
return Returns a value from a method.
short Defines a short type.
static Specifies that a variable or method belongs to the class rather than instances of the class.
strictfp Specifies that floating-point calculations are performed as defined by the IEEE 754 standard.
super Refers to the superclass of an object.
switch Specifies a switch statement.
synchronized Specifies that a method can only be accessed by one thread at a time.
this Refers to the current object.
throw Throws an exception.
throws Specifies the exceptions that a method can throw.
transient Specifies that a variable is not part of the persistent state of an object.
try Specifies a block of code to try, and handles exceptions with catch and/or finally.
void Specifies that a method does not return a value.
volatile Specifies that a variable may be changed unexpectedly by another thread.
while Starts a while loop.

Example

public class Example {
    // Declaration of a constant variable
    public static final int MAX_SIZE = 100;

    // Declaration of an abstract method
    public abstract void display();

    // Declaration of a method with boolean return type
    public boolean isValid(int value) {
        return value > 0;
    }

    public static void main(String[] args) {
        // Declaration and instantiation of an object
        Example obj = new Example();

        // Switch statement with case branches
        int choice = 2;
        switch (choice) {
            case 1:
                System.out.println("Choice 1 selected");
                break;
            case 2:
                System.out.println("Choice 2 selected");
                break;
            default:
                System.out.println("Invalid choice");
        }

        // Looping construct using while loop
        int i = 0;
        while (i < 5) {
            System.out.println("Iteration " + i);
            i++;
        }
    }
}

This example demonstrates the use of various Java keywords such as abstract, final, boolean, switch, case, default, while, public, static, void, int, return, new, and System.out.println. Each keyword serves a specific purpose in defining the behavior and structure of the Java program.

Summary

Java keywords play crucial roles in defining the structure, behavior, and flow of Java programs. Understanding these keywords is essential for writing correct and efficient Java code.

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