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Methods and Constructors in Java

Yasin Cakal

In this article, we will discuss methods and constructors with Java. Methods and constructors are both important concepts in the world of programming, and they are especially important when it comes to working with data structures and algorithms in Java. We will discuss what methods and constructors are, the differences between them, and how to use them in Java. We will also provide some code examples to illustrate the different concepts.

What are Methods and Constructors?

A method is a piece of code that performs a specific task. It is a set of instructions that can be reused and called upon in a program. Methods are defined with a return type and a name. They can also take in arguments, which are pieces of data that are used as input by the method.

A constructor is a special method that is used to create an object. It is called when an instance of a class is created and it initializes the instance variables of the object. Constructors are also used to allocate memory for the objects.

Differences between Methods and Constructors

Methods and constructors are similar in the sense that they are both used to perform tasks, but they are different in a few key ways.

First, methods are used to perform an operation on the data, while constructors are used to create objects. Constructors also have special rules when it comes to their names. Constructors must have the same name as the class that they are a part of.

In addition, constructors do not have a return type. This means that they cannot return a value, while methods can.

Methods in Java

We can create a method in Java using the following syntax:

public <return_type> <method_name>(<parameter_list>) { 
  // code to execute 
  return <return_value>; 
}

The return type is the type of data that the method will return. It can be any valid data type or the keyword void, which means that the method does not return anything. The method name is the name of the method. The parameter list is a comma-separated list of the parameters that the method takes in. The code inside the method is the code that will be executed when the method is called. The return statement is used to return a value from the method.

Constructors in Java

We can create a constructor in Java using the following syntax:

public <class_name>(<parameter_list>) { 
  // code to execute 
}

The class name is the name of the class that the constructor belongs to. The parameter list is a comma-separated list of the parameters that the constructor takes in. The code inside the constructor is the code that will be executed when the constructor is called.

Using Methods and Constructors

We can use methods and constructors to perform various tasks in our program. Methods can be used to perform calculations, manipulate data, and more. Constructors can be used to create objects and allocate memory for them.

Let’s look at an example of a method and a constructor. We will create a class called Student and a method called getName() and a constructor for the class.

public class Student { 
  // instance variables 
  String name; 
  int age; 
  
  // constructor 
  public Student(String name, int age) { 
    this.name = name; 
    this.age = age; 
  } 
  
  // method 
  public String getName() { 
    return this.name; 
  } 
}

In this example, we have created a class called Student and a constructor that takes in a name and an age. The constructor is used to initialize the instance variables of the object. We also have a method called getName() that returns the name of the student.

Conclusion

In this article, we discussed methods and constructors in Java. We discussed what they are and the differences between them. We also looked at how to create methods and constructors in Java and how to use them in a program.

Exercises

Create a class called Car and a constructor that takes in a make, model, and year. The constructor should initialize these instance variables.

public class Car { 
  // instance variables 
  String make; 
  String model; 
  int year; 
  
  // constructor 
  public Car(String make, String model, int year) { 
    this.make = make; 
    this.model = model; 
    this.year = year; 
  } 
}

Create a method called getMake() in the Car class that returns the make of the car.

public String getMake() { 
  return this.make; 
}

Create a class called BankAccount and a constructor that takes in an account number and a balance. The constructor should initialize these instance variables.

public class BankAccount { 
  // instance variables 
  int accountNumber; 
  double balance; 
  
  // constructor 
  public BankAccount(int accountNumber, double balance) { 
    this.accountNumber = accountNumber; 
    this.balance = balance; 
  } 
}

Create a method called deposit() in the BankAccount class that takes in an amount and adds it to the current balance.

public void deposit(double amount) { 
  this.balance += amount; 
}

Create a class called Employee and a constructor that takes in a name and salary. The constructor should initialize these instance variables.

public class Employee { 
  // instance variables 
  String name; 
  double salary; 
  
  // constructor 
  public Employee(String name, double salary) { 
    this.name = name; 
    this.salary = salary; 
  } 
}

Data Structures and Algorithms with Java

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