MCS024 : Question 1 (c) Constructor Vs Method in Java | June 2023 Paper Solution

Question 1. (c) Differentiate between constructor and method, give example for both.

Answer:

Constructor and method are both important components in object-oriented programming, but they serve different purposes. Here's a differentiation between constructors and methods, along with examples for each:

Constructor:

1. Purpose: A constructor is a special method that is used to initialize objects. It is called automatically when an object is created from a class.

2. Naming: Constructors have the same name as the class they belong to.

3. Return Type: Constructors do not have a return type. They do not explicitly return any value.

4. Invocation: Constructors are invoked using the `new` keyword when creating an object.

5. Multiple Constructors: A class can have multiple constructors, allowing for different ways to initialize objects.

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6. Example:

public class Car {
private String brand;
private String color;

// Parameterized constructor
public Car(String brand, String color) {
this.brand = brand;
this.color = color;
}

// Default constructor
public Car() {
this.brand = "Unknown";
this.color = "Black";
}
}

In the example above, the `Car` class has two constructors. The first constructor takes brand and color as parameters and initializes the corresponding instance variables. The second constructor is a default constructor that sets the brand to "Unknown" and the color to "Black" if no values are provided.

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Method:

1. Purpose: A method is a set of instructions that perform a specific action or provide some functionality within a class.

2. Naming: Methods have unique names within a class that reflect the action they perform.

3. Return Type: Methods have a return type that indicates the type of value they return or use `void` if they don't return anything.

4. Invocation: Methods are called explicitly by name, followed by parentheses that may contain arguments.

5. Example:

public class Calculator {

// Addition method
public int add(int num1, int num2) {
return num1 + num2;
}

// Subtraction method
public int subtract(int num1, int num2) {
return num1 - num2;
}

// Multiplication method
public int multiply(int num1, int num2) {
return num1 * num2;
}

// Division method
public double divide(double num1, double num2) {
return num1 / num2;
}
}

In the example above, the `Calculator` class contains different methods for performing arithmetic operations. Each method takes input parameters and returns a result based on the calculations performed.

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To summarize, constructors are special methods used for object initialization and have the same name as the class. They are invoked automatically when an object is created. On the other hand, methods are used for performing actions or providing functionality within a class, have unique names, and are called explicitly.