Method calling in Java

Introduction

Method calling lets you use a set of instructions again and again without rewriting them.

When you want to organize your code into small reusable parts.

When you need to perform the same action multiple times in different places.

When you want to make your program easier to read and understand.

When you want to test parts of your program separately.

When you want to break a big problem into smaller steps.

Syntax

Java

objectName.methodName(arguments);

objectName is the name of the object whose method you want to use.

methodName is the name of the method you want to call.

Examples

Calls the println method to print text on the screen.

Java

System.out.println("Hello World");

Calls the startEngine method on the myCar object.

Java

myCar.startEngine();

Calls the add method with two numbers and stores the result.

Java

int sum = calculator.add(5, 3);

Sample Program

This program defines a method called greet that prints a message. The main method calls greet to show how method calling works.

Java

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

    public static void main(String[] args) {
        greet(); // calling the greet method
        System.out.println("Back in main method.");
    }
}

Important Notes

You can call methods from other methods to reuse code.

If a method needs information, you pass it as arguments inside the parentheses.

Methods can return values that you can use after calling them.

Summary

Method calling runs a set of instructions saved in a method.

It helps keep code organized and reusable.

You call a method using its name and parentheses, optionally with arguments.

Practice

1. What does calling a method in Java do?
myMethod();

easy

A. Runs the instructions inside the method named myMethod.

B. Creates a new method called myMethod.

C. Deletes the method myMethod from the program.

D. Prints the name myMethod on the screen.

Solution

1. Step 1: Understand what a method call does

   Calling a method means running the code inside that method.

2. Step 2: Analyze the example myMethod();

   This runs the instructions saved inside the method named myMethod.

3. Final Answer:

   Runs the instructions inside the method named myMethod. -> Option A

4. Quick Check:

   Method call = run method code [OK]

Hint: Method call runs code inside method name() [OK]

Common Mistakes:

• Thinking method call creates or deletes methods
• Confusing method call with printing text
• Assuming method call changes method definition

2. Which of the following is the correct way to call a method named displayMessage in Java?

easy

A. run displayMessage();

B. call displayMessage();

C. displayMessage;

D. displayMessage();

Solution

1. Step 1: Recall Java method call syntax

   In Java, you call a method by writing its name followed by parentheses.

2. Step 2: Check each option

   Only displayMessage(); matches the correct syntax for calling a method.

3. Final Answer:

   displayMessage(); -> Option D

4. Quick Check:

   Method call syntax = name() [OK]

Hint: Method call needs parentheses after name [OK]

Common Mistakes:

• Omitting parentheses when calling methods
• Adding extra words like 'call' or 'run'
• Using semicolon without parentheses

3. What is the output of this Java code?

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

medium

A. sayHi()

B. No output

C. Hi there!

D. Compilation error

Solution

1. Step 1: Identify the method call in main

   The main method calls sayHi(), which prints "Hi there!".

2. Step 2: Understand what sayHi() does

   It prints the text "Hi there!" to the screen.

3. Final Answer:

   Hi there! -> Option C

4. Quick Check:

   Method prints text = output text [OK]

Hint: Method prints text, so output is printed string [OK]

Common Mistakes:

• Confusing method name with output
• Expecting no output without print statement
• Thinking method call causes error

4. Find the error in this Java code snippet:

public class Demo {
  public static void greet() {
    System.out.println("Hello!");
  }
  public static void main(String[] args) {
    greet;
  }
}

medium

A. Incorrect method name.

B. Missing parentheses when calling method greet.

C. Missing semicolon after greet.

D. Method greet is not defined.

Solution

1. Step 1: Check method call syntax in main

   The code uses greet; which is missing parentheses.

2. Step 2: Understand correct method call

   Method calls require parentheses even if no arguments: greet();.

3. Final Answer:

   Missing parentheses when calling method greet. -> Option B

4. Quick Check:

   Method call needs () [OK]

Hint: Always use () to call methods, even if empty [OK]

Common Mistakes:

• Forgetting parentheses on method calls
• Thinking semicolon alone calls method
• Assuming method call without () is valid

5. Given this Java code:

public class Calculator {
  public static int add(int a, int b) {
    return a + b;
  }
  public static void main(String[] args) {
    int result = add(5, 3);
    System.out.println(result);
  }
}

What will be printed when the program runs?

hard

A. 8

B. 53

C. add(5, 3)

D. Compilation error

Solution

1. Step 1: Understand method add parameters and return

   The method add takes two integers and returns their sum.

2. Step 2: Analyze the call add(5, 3)

   It returns 5 + 3 = 8, which is stored in result.

3. Step 3: Check the output statement

   System.out.println(result); prints the value 8.

4. Final Answer:

   8 -> Option A

5. Quick Check:

   Sum of 5 and 3 = 8 [OK]

Hint: Method returns sum; print shows result [OK]

Common Mistakes:

• Concatenating numbers as strings instead of adding
• Expecting method name printed instead of result
• Confusing return value with method call syntax