Static methods in Java - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a static method named greet.

Java

public class Hello {
    public static void [1]() {
        System.out.println("Hello, world!");
    }
}

Drag options to blanks, or click blank then click option'

Agreet

Brun

Cstart

Dmain

Attempts:

3 left

💡 Hint

Common Mistakes

Using main instead of greet.

Forgetting the method name or misspelling it.

The method name should be greet as specified. Static methods are declared with the static keyword.

2fill in blank

medium

Complete the code to call the static method greet from the main method.

Java

public class Hello {
    public static void greet() {
        System.out.println("Hello, world!");
    }

    public static void main(String[] args) {
        [1]();
    }
}

Drag options to blanks, or click blank then click option'

AHello.greet

Bnew Hello().greet

Cgreet

Dthis.greet

Attempts:

3 left

💡 Hint

Common Mistakes

Using this.greet() which is invalid in static context.

Trying to create an object to call a static method.

Inside the same class, static methods can be called directly by their name without class name or object.

3fill in blank

hard

Fix the error in calling the static method greet from another class named App.

Java

public class Hello {
    public static void greet() {
        System.out.println("Hello from Hello class!");
    }
}

public class App {
    public static void main(String[] args) {
        [1]();
    }
}

Drag options to blanks, or click blank then click option'

AHello.greet

Bgreet

CApp.greet

Dnew Hello().greet

Attempts:

3 left

💡 Hint

Common Mistakes

Calling greet() without class name from another class.

Trying to call App.greet() when greet is not in App.

To call a static method from another class, use the class name followed by the method name.

4fill in blank

hard

Fill both blanks to create a static method square that returns the square of an integer.

Java

public class MathUtils {
    public static int [1](int num) {
        return num [2] num;
    }
}

Drag options to blanks, or click blank then click option'

Asquare

B*

C+

Dmultiply

Attempts:

3 left

💡 Hint

Common Mistakes

Using + instead of * which adds instead of multiplies.

Naming the method incorrectly.

The method name should be square. The multiplication operator * calculates the square.

5fill in blank

hard

Fill all three blanks to create a static method isEven that returns true if a number is even, otherwise false.

Java

public class NumberUtils {
    public static boolean [1](int n) {
        return n [2] 2 [3] 0;
    }
}

Drag options to blanks, or click blank then click option'

AisEven

B%

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using != instead of == which reverses the logic.

Incorrect method name.

The method name is isEven. The modulus operator % checks remainder. If remainder equals zero, the number is even.

Practice

1. Which statement about static methods in Java is true?

easy

A. Static methods belong to the class and can be called without creating an object.

B. Static methods can only be called on objects of the class.

C. Static methods can access instance variables directly.

D. Static methods must always return void.

Solution

1. Step 1: Understand what static means

   Static methods belong to the class itself, not to any object instance.

2. Step 2: Check method calling rules

   Static methods can be called using the class name without creating an object.

3. Final Answer:

   Static methods belong to the class and can be called without creating an object. -> Option A

4. Quick Check:

   Static method = class method call [OK]

Hint: Static methods use class name, no object needed [OK]

Common Mistakes:

• Thinking static methods need an object to call
• Assuming static methods access instance variables
• Believing static methods must return void

2. Which of the following is the correct way to declare a static method in Java?

easy

A. public void static myMethod() {}

B. static void public myMethod() {}

C. public static void myMethod() {}

D. void static public myMethod() {}

Solution

1. Step 1: Recall Java method declaration order

   In Java, the correct order is access modifier, then static keyword, then return type, then method name.

2. Step 2: Match the correct syntax

   public static void myMethod() {} follows this order: public static void myMethod() {}.

3. Final Answer:

   public static void myMethod() {} -> Option C

4. Quick Check:

   Access + static + return type = correct order [OK]

Hint: Remember: access modifier before static keyword [OK]

Common Mistakes:

• Placing static after return type
• Omitting access modifier
• Mixing order of keywords

3. What will be the output of the following code?

public class Test {
    static int count = 0;
    static void increment() {
        count++;
    }
    public static void main(String[] args) {
        increment();
        increment();
        System.out.println(count);
    }
}

medium

A. 2

B. 1

C. Compilation error

D. 0

Solution

1. Step 1: Understand static variable and method behavior

   The static variable count starts at 0 and is shared by all calls.

2. Step 2: Trace method calls

   Each call to increment() increases count by 1. Called twice, count becomes 2.

3. Final Answer:

   2 -> Option A

4. Quick Check:

   Two increments = count 2 [OK]

Hint: Static variables keep value across static method calls [OK]

Common Mistakes:

• Thinking count resets each call
• Confusing static and instance variables
• Expecting compilation error due to static usage

4. Identify the error in the following code snippet:

public class Example {
    int x = 5;
    static void printX() {
        System.out.println(x);
    }
}

medium

A. Missing return type for printX method.

B. Cannot use instance variable x inside static method printX.

C. Static methods cannot have print statements.

D. Class Example must be declared static.

Solution

1. Step 1: Check static method access rules

   Static methods cannot access instance variables directly because they belong to the class, not an object.

2. Step 2: Identify the error in code

   Method printX() tries to print instance variable x without an object, causing an error.

3. Final Answer:

   Cannot use instance variable x inside static method printX. -> Option B

4. Quick Check:

   Static method can't access instance variables directly [OK]

Hint: Static methods can't use instance variables directly [OK]

Common Mistakes:

• Assuming static methods can access instance variables
• Thinking static methods need return type fix
• Believing classes must be static

5. You want to create a utility class MathUtils with a static method square(int n) that returns the square of a number. Which implementation is correct?

hard

A. public class MathUtils { public int square(int n) { return n * n; } }

B. public class MathUtils { static void square(int n) { return n * n; } }

C. public static class MathUtils { public int square(int n) { return n * n; } }

D. public class MathUtils { public static int square(int n) { return n * n; } }

Solution

1. Step 1: Identify static method requirements

   The method should be static to call without creating an object.

2. Step 2: Check method signature and return type

   Method must return int and be declared static with proper access modifier.

3. Step 3: Validate options

   public class MathUtils { public static int square(int n) { return n * n; } } correctly declares a public static method returning int.

4. Final Answer:

   public class MathUtils { public static int square(int n) { return n * n; } } -> Option D

5. Quick Check:

   Static method with return type and public access [OK]

Hint: Utility methods should be static with correct return type [OK]

Common Mistakes:

• Omitting static keyword
• Using void return type when returning value
• Declaring class static incorrectly