constructor or method

Marie Mabry

I cannot figure out how the constructor differs from the method in Java. For me personally, the only difference is using the special word "this" in constructor. I would like to distinguish between their functions and structure. Help me understand, please.

5 Replies

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Satya Karki5y ago
Hi,

Following are the difference between constructor and method.

Constructor is used to initialize an object whereas method is used to exhibits functionality of an object.
Constructors are invoked implicitly whereas methods are invoked explicitly.
Constructor does not return any value where the method may/may not return a value.
In case constructor is not present, a default constructor is provided by java compiler. In the case of a method, no default method is provided.
Constructor should be of the same name as that of class. Method name should not be of the same name as that of class.
Check this blog: https://www.tutorialspoint.com/Difference-between-constructor-and-method-in-Java

+3
Rijwan Ansari5y ago
Hi,

You can get idea form this example:
public class ClassName{
  int modelYear;
  String modelName;

// this is your constructor
  public ClassName(int year, String name) {
    modelYear = year;
    modelName = name;
  }

// this is your mothod
  public bool DoSomeWork(int wordId) {
    //method logic
   // use can use modelYear, ModelName in every or any mothods.
  }
}

// another class
public class AnotherName{
  //

  Public bool ThisClassFunction
  {
   ClassName objClassName = new ClassName(1969, "Mustang");// must pass parameter as it is defined in costructor
    bool isCheck = objClassName.DoSomeWork(121); // then only you can call the function for ClassName
   //ClassName objClassName = new ClassName(); // without parameter will thow error, but you can define multiple contructor.
    }
We use contructor to initiate the class, if there is no any contructor then parameterless constructor is there by default. We can initiate contructor with parameters to pass some values/object in order to use throughout the class so that we don't need to pass/define in each function.
Regards
Rijwan
+3
Sachin Singh5y ago
Constructor of a house, means the people who construct the house.
Constructor in object oriented language means the method who construct the objects.
suppose you have a class with members of type int, string etc.
you are a lazy developer, you will definitely forget to initialize the members, but compiler won't accept it so the compiler will itself create a default constructor which will assign default values to class members like int to 0 and string to null.
if you don't want these default values then you can create parameterized constructor, then whenever you will try to create a class object then you will have to explictely pass the values for members for initilization.
+4
Salman Beg5y ago
Check this link which explain in detail, https://www.tutorialspoint.com/Difference-between-constructor-and-method-in-Java
+2
Aman Gupta5y ago
The definitions of constructors and methods look similar in code. They can take parameters, they can have modifiers (e.g. public), and they have method bodies in braces.
The important difference between constructors and methods is that constructors initialize objects that are being created with the new operator, while methods perform operations on objects that already exist.
Constructors can't be called directly; they are called implicitly when the new keyword creates an object. Methods can be called directly on an object that has already been created with new.
Constructors must be named with the same name as the class name. They can't return anything, even void (the object itself is the implicit return).
Methods must be declared to return something, but constructors don't return anything.

Hope this makes sense.
Thanks.
+1