Default access modifier in Java - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the default access modifier in Java when none is specified?

The default access modifier is package-private, meaning the member or class is accessible only within its own package.

beginner

Which classes can access a member with default access modifier?

Only classes in the same package can access members with the default access modifier.

beginner

True or False: A default access modifier member is accessible from subclasses in different packages.

False. Default access members are not accessible outside their package, even by subclasses.

beginner

Code snippet:<br><pre>class Example {
  int number = 5; // no access modifier
}</pre><br>What is the access level of 'number'?

The 'number' field has default (package-private) access, so it is accessible only within the same package.

intermediate

Why might a developer use the default access modifier?

To restrict access to classes or members within the same package, promoting encapsulation without making them public.

What is the scope of a member with default access modifier in Java?

A Accessible from any package

B Accessible from subclasses in any package

C Accessible only within the same class

D Accessible only within the same package

Default access means package-private, so the member is accessible only within its own package.

If no access modifier is specified for a class member, what is its access level?

A public

B private

C default (package-private)

D protected

When no modifier is given, Java assigns default access, which is package-private.

Can a class in a different package access a default access member?

A No, never

B Only if it is a subclass

C Yes, always

D Only if it imports the package

Default access restricts visibility to the same package only.

Which keyword is used to declare default access modifier explicitly?

A package

B none (no keyword)

C default

D private

Default access is implied by not specifying any access modifier.

Which of these is NOT an access modifier in Java?

A default

B public

C protected

D private

"default" is not a keyword; it is the name given to the access level when no modifier is specified.

Explain what the default access modifier means in Java and when it is applied.

Think about what happens if you don't write public, private, or protected.

Describe a scenario where using the default access modifier is beneficial.

Consider teamwork on a project where some parts should be hidden from outside.

Practice

1. Which statement best describes the default access modifier in Java?

easy

A. It restricts access only to the class itself.

B. It allows access from any package using the default keyword.

C. It allows access only within the same package without using any keyword.

D. It allows access only to subclasses in other packages.

Solution

1. Step 1: Understand default access modifier meaning

   The default access modifier means no keyword is used before a class, method, or variable, and it restricts access to the same package only.

2. Step 2: Compare options with definition

   It allows access only within the same package without using any keyword. correctly states it allows access only within the same package and requires no keyword. Other options mention keywords or access outside the package, which is incorrect.

3. Final Answer:

   It allows access only within the same package without using any keyword. -> Option C

4. Quick Check:

   Default access = package-only access [OK]

Hint: No keyword means default access is package-only [OK]

Common Mistakes:

• Thinking default requires a keyword
• Confusing default with public or private
• Assuming default allows access from other packages

2. Which of the following is the correct way to declare a class with default access modifier?

easy

A. class MyClass {}

B. private class MyClass {}

C. default class MyClass {}

D. public class MyClass {}

Solution

1. Step 1: Recall syntax for default access modifier

   Default access means no access keyword is written before the class name.

2. Step 2: Check each option

   class MyClass {} declares the class without any access keyword, which means default access. Options A and B use explicit keywords, and C uses a non-existent keyword.

3. Final Answer:

   class MyClass {} -> Option A

4. Quick Check:

   No keyword = default access [OK]

Hint: No keyword before class means default access [OK]

Common Mistakes:

• Using 'default' keyword which does not exist in Java
• Confusing private with default
• Always using public by habit

3. Consider two classes in the same package:

class A {
    void show() {
        System.out.println("Hello from A");
    }
}

class B {
    public static void main(String[] args) {
        A a = new A();
        a.show();
    }
}

What will be the output when class B is run?

medium

A. Compile-time error: show() has private access

B. Hello from A

C. Compile-time error: class A is not public

D. Runtime error

Solution

1. Step 1: Analyze access modifiers in the code

   Class A and method show() have default access (no keyword). Both classes are in the same package, so access is allowed.

2. Step 2: Predict program output

   Since B can access A and its show() method, the program prints "Hello from A" without errors.

3. Final Answer:

   Hello from A -> Option B

4. Quick Check:

   Default access allows same package access [OK]

Hint: Default access works within same package [OK]

Common Mistakes:

• Assuming default means private access
• Thinking class A must be public to be used
• Confusing compile-time and runtime errors

4. Given two packages pkg1 and pkg2, and these classes:

package pkg1;
class C {
    void display() {
        System.out.println("Inside C");
    }
}

package pkg2;
import pkg1.C;
public class D {
    public static void main(String[] args) {
        C c = new C();
        c.display();
    }
}

What is the error in this code?

medium

A. Cannot access class C from pkg2 because it has default access

B. Cannot call display() because it is private

C. Cannot import package pkg1

D. No error, code runs fine

Solution

1. Step 1: Check class C's access modifier and package

   Class C has default access (no keyword) and is in package pkg1, so it is accessible only within pkg1.

2. Step 2: Check usage of C in pkg2

   Class D in pkg2 tries to create an instance of C and call display(), but C is not visible outside pkg1, causing a compile-time error.

3. Final Answer:

   Cannot access class C from pkg2 because it has default access -> Option A

4. Quick Check:

   Default access = package-only visibility [OK]

Hint: Default access blocks cross-package access [OK]

Common Mistakes:

• Assuming default access allows cross-package use
• Thinking display() is private
• Confusing import errors with access errors

5. You have a package tools with classes:

class Helper {
    void assist() {
        System.out.println("Helping...");
    }
}

public class Tool {
    public static void main(String[] args) {
        Helper h = new Helper();
        h.assist();
    }
}

You want to allow only classes inside tools to use Helper and its assist() method, but prevent access from outside. Which is the best way to achieve this?

hard

A. Make Helper and assist() public.

B. Use protected for Helper and assist().

C. Make Helper and assist() private.

D. Keep Helper and assist() with default access (no keyword).

Solution

1. Step 1: Understand access goals

   You want Helper and assist() accessible only inside the same package (tools) and hidden outside.

2. Step 2: Match access modifiers to goals

   Default access (no keyword) restricts access to the same package only, which fits the requirement. Public allows all access, private restricts to the class only, and protected allows subclasses and package access.

3. Final Answer:

   Keep Helper and assist() with default access (no keyword). -> Option D

4. Quick Check:

   Default access = package-only visibility [OK]

Hint: Default access hides from outside packages [OK]

Common Mistakes:

• Using public which exposes to all packages
• Using private which hides even inside package
• Using protected which allows subclass access outside package