Why methods are needed in Java - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a method that prints a greeting.

Java

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

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

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

Agreet

Bmain

Cprint

Dhello

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different method name than the one called in main.

Confusing method name with class name.

The method name must be greet to match the call in main.

2fill in blank

medium

Complete the code to call the method that calculates the sum.

Java

public class Calculator {
    public static int sum(int a, int b) {
        return a + b;
    }

    public static void main(String[] args) {
        int result = [1](5, 3);
        System.out.println(result);
    }
}

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

Atotal

Bsum

Ccalculate

Dadd

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a method name that does not exist.

Using a variable name instead of a method name.

The method to call is named sum, which adds two numbers.

3fill in blank

hard

Fix the error by completing the method call correctly.

Java

public class Printer {
    public static void printMessage(String message) {
        System.out.println(message);
    }

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

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

Aprint

Bprintln

CprintMessage

Dmessage

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name that does not exist.

Using a variable name instead of a method name.

The method to call is printMessage which takes a String argument.

4fill in blank

hard

Fill both blanks to create a method that returns the square of a number and call it.

Java

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

    public static void main(String[] args) {
        int sq = square(4);
        System.out.println(sq);
    }
}

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

Asquare

B+

C*

Dmultiply

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of multiplication.

Using a method name that does not match the call.

The method name is square and the multiplication operator * is used to calculate the square.

5fill in blank

hard

Fill all three blanks to create a method that checks if a number is even and call it.

Java

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

    public static void main(String[] args) {
        boolean result = isEven(10);
        System.out.println(result);
    }
}

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

AisEven

B%

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect method name.

Using wrong operators for checking evenness.

The method name is isEven. The modulus operator % checks the remainder, and == compares it to zero to confirm evenness.

Practice

1. Why do we use methods in Java programs?

easy

A. To organize code into reusable blocks

B. To make the program run faster

C. To avoid using variables

D. To write code without errors

Solution

1. Step 1: Understand the purpose of methods

   Methods group code that performs a specific task so it can be reused easily.

2. Step 2: Compare options with method benefits

   Only organizing code into reusable blocks matches the main reason for methods.

3. Final Answer:

   To organize code into reusable blocks -> Option A

4. Quick Check:

   Methods = reusable code blocks [OK]

Hint: Methods help reuse code easily [OK]

Common Mistakes:

• Thinking methods make code run faster
• Believing methods remove the need for variables
• Assuming methods fix all errors automatically

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

easy

A. greet void() { System.out.println("Hello"); }

B. void greet() System.out.println("Hello");

C. void greet[] { System.out.println("Hello"); }

D. void greet() { System.out.println("Hello"); }

Solution

1. Step 1: Check method declaration syntax

   In Java, a method declaration starts with return type, method name, parentheses, and braces.

2. Step 2: Identify the correct syntax

   void greet() { System.out.println("Hello"); } follows this pattern correctly: 'void greet() { ... }'. Others have syntax errors.

3. Final Answer:

   void greet() { System.out.println("Hello"); } -> Option D

4. Quick Check:

   Method syntax = returnType name() { } [OK]

Hint: Method syntax: returnType name() { } [OK]

Common Mistakes:

• Placing return type after method name
• Using brackets [] instead of parentheses ()
• Omitting curly braces {}

3. What will be the output of this Java code?

public class Test {
  static void sayHi() {
    System.out.println("Hi there!");
  }
  public static void main(String[] args) {
    sayHi();
    sayHi();
  }
}

medium

A. !ereht iH
!ereht iH

B. Hi there!
Hi there!

C. Hi there! Hi there!

D. Hi there!
Hi there!
Hi there!

Solution

1. Step 1: Understand method calls in main

   The method sayHi() prints "Hi there!" once per call. It is called twice.

2. Step 2: Determine output format

   Each call prints "Hi there!" followed by a new line. Two calls print two lines.

3. Final Answer:

   Hi there! Hi there! -> Option B

4. Quick Check:

   Two calls print two lines [OK]

Hint: Each println adds a new line [OK]

Common Mistakes:

• Ignoring new lines after println
• Thinking output is on one line
• Confusing escape sequences with actual output

4. Find the error in this method declaration:

public void printMessage {
  System.out.println("Hello");
}

medium

A. Missing parentheses after method name

B. Missing return type

C. Missing semicolon after println

D. Method name is invalid

Solution

1. Step 1: Check method declaration syntax

   Methods must have parentheses after the name, even if no parameters are used.

2. Step 2: Identify the missing part

   The code misses parentheses after printMessage, causing a syntax error.

3. Final Answer:

   Missing parentheses after method name -> Option A

4. Quick Check:

   Method() needs parentheses [OK]

Hint: Always add () after method name [OK]

Common Mistakes:

• Forgetting parentheses in method declaration
• Thinking semicolon needed after method header
• Assuming method name can have spaces

5. You want to write a Java program that calculates the area of a rectangle multiple times with different sizes. Why is it better to use a method for this task?

hard

A. Because methods automatically print the result without extra code

B. Because methods make the program run faster by skipping calculations

C. Because methods allow you to write the area calculation once and reuse it with different inputs

D. Because methods prevent the program from crashing

Solution

1. Step 1: Understand the problem of repeated calculations

   Calculating area multiple times means repeating the same code with different values.

2. Step 2: See how methods help

   Methods let you write the calculation once and call it with different inputs, avoiding repetition.

3. Final Answer:

   Because methods allow you to write the area calculation once and reuse it with different inputs -> Option C

4. Quick Check:

   Methods = reuse code with different inputs [OK]

Hint: Use methods to avoid repeating code [OK]

Common Mistakes:

• Thinking methods speed up calculations automatically
• Believing methods print results without code
• Assuming methods fix runtime errors