Java is a popular programming language that is widely used in the development of different applications. In Java, there are several access modifiers, namely public, private, and protected, which are used to control access to class members such as variables, constructors, and methods. In this article, we will discuss the differences between the public, private, and protected modifiers in Java, with code examples.
Public Modifier
The public modifier is the most permissive of the access modifiers in Java. It allows unrestricted access to class members, which means that they can be accessed from any part of the program, including other classes. To declare a class member as public, you simply preface the declaration with the keyword 'public'.
For instance, consider the following example:
public class Person {
public String name;
public int age;
}
In the above example, we have declared two class members, namely 'name' and 'age', as public. This means that they can be accessed and modified anywhere in the program, including other classes.
Private Modifier
The private modifier is the most restrictive of the access modifiers in Java. It restricts access to class members to within the class that they are declared in, which means that they cannot be accessed from any other class. To declare a class member as private, you simply preface the declaration with the keyword 'private'.
For instance, consider the following example:
public class Person {
private String name;
private int age;
}
In the above example, we have declared two class members, namely 'name' and 'age', as private. This means that they cannot be accessed or modified outside the class. Only methods within the class can access and modify them.
Protected Modifier
The protected modifier is somewhat similar to the private modifier except that it allows access to class members from subclasses as well as within the class that they are declared in. To declare a class member as protected, you preface the declaration with the keyword 'protected'.
For instance, consider the following example:
public class Person {
protected String name;
protected int age;
}
In the above example, we have declared two class members, namely 'name' and 'age', as protected. This means that they can be accessed and modified within the class as well as from subclasses.
Code Examples
To further illustrate the differences between the public, private, and protected modifiers in Java, we will use code examples. Consider the following class hierarchy:
public class Animal {
public String name;
private int age;
protected String color;
public Animal(String name, int age, String color) {
this.name = name;
this.age = age;
this.color = color;
}
public void displayInfo() {
System.out.println("Name: " + name);
System.out.println("Age: " + age);
System.out.println("Color: " + color);
}
}
public class Dog extends Animal {
public Dog(String name, int age, String color) {
super(name, age, color);
}
public void bark() {
System.out.println("Woof!");
}
}
public class Main {
public static void main(String[] args) {
Animal animal = new Animal("Tiger", 10, "Orange");
Dog dog = new Dog("Buddy", 5, "Black");
animal.name = "Lion";
animal.age = 15;
animal.color = "Yellow";
dog.name = "Max";
// dog.age = 7; // Compile-time error
dog.color = "Brown";
animal.displayInfo();
dog.displayInfo();
dog.bark();
}
}
In the above example, we have a class hierarchy consisting of three classes, namely Animal, Dog, and Main. The Animal class has three class members, namely 'name', 'age', and 'color', which are declared with public, private, and protected modifiers, respectively.
The Dog class extends the Animal class and therefore inherits the name, age, and color properties. It also has a new method called 'bark', which prints out "Woof!" to the console.
In the Main class, we create an instance of the Animal class and the Dog class. We then modify the public and protected properties of the Animal and Dog classes, respectively. However, we cannot modify the private property of the Animal class outside of the class. Finally, we call the 'displayInfo' and 'bark' methods to display the information on the console.
Conclusion
In conclusion, access modifiers are important in any programming language that supports object-oriented programming, including Java. The public modifier allows unrestricted access to class members, the private modifier restricts access to class members to within the class, while the protected modifier allows access to class members from subclasses as well as within the class that they are declared in. Understanding these access modifiers is crucial to developing reusable and maintainable code in Java and other object-oriented programming languages.
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Popular questions
Sure, here are some questions and answers about the differences between the public, private, and protected modifiers in Java:
-
What is the public modifier in Java?
Ans: The public modifier in Java is the most permissive of the access modifiers. It allows unrestricted access to class members, which means that they can be accessed from any part of the program, including other classes. -
What is the private modifier in Java?
Ans: The private modifier in Java is the most restrictive of the access modifiers. It restricts access to class members to within the class that they are declared in, which means that they cannot be accessed from any other class. -
What is the protected modifier in Java?
Ans: The protected modifier in Java is somewhat similar to the private modifier except that it allows access to class members from subclasses as well as within the class that they are declared in. -
What is an example of a public member in Java?
Ans: An example of a public member in Java is a public method that can be accessed from any part of the program. For instance, consider the following example:
public class Student {
public String name;
public void setName(String name) {
this.name = name;
}
}
In the above example, the 'name' variable and 'setName' method are declared public, which means that they can be accessed and modified from any part of the program.
- What is an example of a private member in Java?
Ans: An example of a private member in Java is a private variable that can only be accessed within the class. For instance, consider the following example:
public class BankAccount {
private double balance;
public void deposit(double amount) {
balance += amount;
}
public void withdraw(double amount) {
if (amount > balance) {
System.out.println("Insufficient funds.");
} else {
balance -= amount;
}
}
}
In the above example, the 'balance' variable is declared private, which means that it can only be accessed and modified within the BankAccount class. The 'deposit' and 'withdraw' methods are declared public and can be accessed from any part of the program.
Tag
Accessibility
