Difference between constructor and methods

Amitabh Pandey

15y2.2kJava

Hello,

What is the difference between constructor and method ?

6 Replies

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Aarti15y ago
Basic difference between constructor and method is Constructor is used to instantiate a object and method represents the behaviour of that object.
0
Datta Kharad15y ago
Hi
Difference between Constructor and Method as follows:

A constructor only works when you create a new instance of a class. This is the very first method to run on an instance, it has to run, and it runs exactly once.

A method on an instance can be called anywhere between zero times to infinite times on an instance once it is created.

A constructor is run implicitly. When a new instance of a class is created, it runs automatically. A method is run explicitly. It has to be called either from some outside source or from a method -or a constructor- in the class.

A constructor is intended to be used for wiring. In the constructor, you want to avoid doing actual work. You basically prepare the class to be used. A method is intended to do actual work.

public class MyType
{
private SomeType _myNeeds;

// constructor
MyClass(SomeType iWillNeedThis)
{
_myNeeds = iWillNeedThis;
}

// method
public void MyMethod()
{
DoSomethingAbout(_myNeeds);
}
}

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0
Aarti15y ago
Hi Amitabh,
Constructor will be automatically invoked when an object is created whereas method has to be called explicitly.
Constructor needs to have the same name as that of the class whereas functions need not be the same.

There is no return type given in a constructor signature (header). The value is this object itself so there is no need to indicate a return value.
There is no return statement in the body of the constructor.
The first line of a constructor must either be a call on another constructor in the same class (using this), or a call on the superclass constructor (using super). If the first line is neither of these, the compiler automatically inserts a call to the parameterless super class constructor.

Thanks.
0
Satyapriya Nayak15y ago
Hi Amitabh,

Please refer the below link

http://www.interviewcorner.com/Answer/Answers.aspx?QuestionId=999&MajorCategoryId=8&MinorCategoryId=41

Thanks
0
Vulpes15y ago
On the first point, the 'new' operator invokes the constructor after allocating sufficient memory on the heap (in the case of reference types) to contain the object's instance fields (initialized to zero) plus some overhead.
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Javeed M Shaikh15y ago
Hi Amitabh,

Following are the differences:

1. A Method needs to be explicitly called while a constructor is invoked automatically.
2. Method can be of any name but a constructor has to be of the same name that of class.
3. The constructor need not have a return type in the signature, so no return value or return statement.
4. If there is no constructor the compiler automatically creates one while running the application.

Please do not forget to mark "Accepted Answer".
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