Java Access Modifiers

Modifiers in Java

• The final modifier is used to make a variable, method, or class constant and unchangeable.
• A final variable cannot be reassigned, a final method cannot be overridden, and a final class cannot be subclassed.

Example of using the final modifier in Java

• final int MAX_VALUE = 100;
• final class FinalClass { ... }

Control Structures in Java

• There are three types of control structures in Java: selection structures (if-else, switch), iteration structures (for, while, do-while), and jump structures (break, continue, return).

Example of using a selection structure (if-else) in Java

• if (x > 0) { System.out.println("Positive number"); } else { System.out.println("Negative number"); }

Static Import Statement in Java

• The static import statement allows members (fields and methods) from a class to be used in the code without specifying the class name.
• It simplifies the usage of static members from a class.

Example of using the static import statement in Java

• import static java.lang.Math.PI;
• double result = PI * 5 * 5;

Default Keyword in a Switch Statement

• The default keyword is used as a way to specify the actions to be taken when none of the cases in the switch statement is true.
• It is similar to the else case in an if-else statement.

Example of using the default keyword in a switch statement

• switch (day) { case 1: System.out.println("Monday"); break; case 2: System.out.println("Tuesday"); break; default: System.out.println("Invalid day"); }

Private Access Modifier in Java

• The private access modifier restricts the accessibility of a class, method, or variable to within the same class.

Example of using the private access modifier

• public class MyClass { private int x; private void myMethod() { ... } }

Abstract Classes and Interfaces

• An abstract class can have abstract and non-abstract methods, while an interface can only have abstract methods.
• A class can implement multiple interfaces, but it can only extend one abstract class.

Example of using an abstract class and an interface

• abstract class AbstractClass { abstract void myMethod(); }
• interface MyInterface { void myMethod(); }

Method Overloading in Java

• Method overloading allows a class to have multiple methods with the same name but different parameters.
• The methods must have different parameter types, order, or number of parameters.

Example of method overloading

• class MathOperations { int add(int a, int b) { ... } double add(double a, double b) { ... } }

Method Overriding in Java

• Method overriding allows a subclass to provide a specific implementation of a method that is already provided by its parent class.

Example of method overriding

• class Animal { void sound() { System.out.println("Animal makes a sound"); } }
• class Dog extends Animal { void sound() { System.out.println("Dog barks"); } }

Packages in Java

• A package is a namespace that organizes a set of related classes and interfaces.
• Packages help in preventing naming conflicts, improve reusability, and control access.

Access Specifiers in Java

• The access specifiers in Java are public, protected, default, and private.
• It provides the highest level of encapsulation and data hiding.

Protected Access Modifier in Java

• The protected access modifier restricts the accessibility of a class, method, or variable to within the same package or subclasses of the class.
• It allows for restricted access to the members of a class.

Example of using the protected access modifier

• package com.mycompany.myapp; public class MyClass { protected int x; protected void myMethod() { ... } }

Super() Method in Java

• The super() method is used to call the constructor of the parent class from the constructor of the child class.
• It is used to initialize the inherited members of the parent class.