Java Access Modifiers

Java access modifiers are used to provide access control in java. Java provides access control through three keywords - private, protected and public. We are not required to use these access modifiers always, so we have another one namely “default access”, “package-private” or “no modifier”.

Java Access Modifiers

We can use java access modifiers with Classes as well as Class variables and methods. We are allowed to use only “public” or “default” access modifiers with java classes.

1. If a class is “public” then we can access it from anywhere, i.e from any other class located in any other packages etc.
2. We can have only one “public” class in a source file and file name should be same as the public class name.
3. If the class has “default access” then it can be accessed only from other classes in the same package.

Java Access Modifiers with Class Member

We can have all the four access modifiers for class member variables and methods. However, member access modifier rules get applied after the class level access rules. For example, if a class is having default access then it will not be visible in other packages and hence methods and variables of the class will also be not visible. We will look into each of them separately and then we will show the java access modifiers usage with a simple program.

Java Access Modifiers - public keyword

If a class member is “public” then it can be accessed from anywhere. The member variable or method is accessed globally. This is the simplest way to provide access to class members. However, we should take care of using this keyword with class variables otherwise anybody can change the values. Usually, class variables are kept as private and getter-setter methods are provided to work with them.

Java Access Modifiers - private keyword

If a class member is “private” then it will be accessible only inside the same class. This is the most restricted access and the class member will not be visible to the outer world. Usually, we keep class variables as private and methods that are intended to be used only inside the class as private.

Java Access Modifiers - protected keyword

If class member is “protected” then it will be accessible only to the classes in the same package and to the subclasses. This modifier is less restricted from private but more restricted from public access. Usually, we use this keyword to make sure the class variables are accessible only to the subclasses.

Java Access Modifiers - default access

If a class member doesn’t have any access modifier specified, then it’s treated with default access. The access rules are similar to classes and the class member with default access will be accessible to the classes in the same package only. This access is more restricted than public and protected but less restricted than private. (Least Accessible) private < default < protected < public (Most Accessible) The below table summarise above access modifiers with respect to different classes in the same package or other packages and subclasses. Let’s write some simple classes where we will see the java access modifiers in action. TestA.java

package com.journaldev.access;

class TestA {

	public void methodPublic(){
		methodPrivate();
	}
	
	protected void methodProtected(){
		methodPrivate();
	}
	
	void methodDefault(){
		methodPrivate();
	}
	
	private void methodPrivate(){}
}

Note that TestA class has default access and the private class method is accessible to all other parts of the same class. TestB.java

package com.journaldev.access;

import com.journaldev.access.TestA;

public class TestB {

	public static void main(String args[]) {
		new TestA().methodPublic();
		new TestA().methodProtected();
		new TestA().methodDefault();

	}

	public void methodPublic() {

	}

	protected void methodProtected() {

	}

	void methodDefault() {

	}

	private void methodPrivate() {
	}

}

Note that TestB is in the same package as TestA class and hence it is able to access it’s class members. private members are not accessible but all other members are accessible because of the same package. TestC.java

package com.journaldev.access.child;

import com.journaldev.access.TestB;

public class TestC {

	public static void main(String[] args) {
		new TestB().methodPublic();
	}

}

TestB class is accessible because it’s public. Only public members of TestB class is accessible because TestC class is not in the same package nor its subclass of TestB. TestE.java

package com.journaldev.util;

import com.journaldev.access.TestB;

public class TestE extends TestB {

	public static void main(String[] args) {
		new TestB().methodPublic();
		new TestB().methodProtected(); // compile time error

		// works, accessing super class protected method using subclass
		new TestE().methodProtected();

	}

}

Since TestE class is a subclass of TestB, we can access TestB protected members through child class TestE. If we try to access the superclass protected method directly, we will get a compile-time error. That’s all for the java access modifiers, it’s simple to understand. Just don’t confuse with the default and protected access. An easy way to remember is that default access is more restricted than protected and protected members are accessible in subclasses. Recently I made a video to explain java access modifiers in detail, you can watch it below on YouTube. https://www.youtube.com/watch?v=QKjnbC3UBtY