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Java Constructors Guide

Constructors are invoked when new objects are created and have the same name as the class. They cannot have a return type or be overridden. Every class has at least one constructor provided either by the programmer or implicitly by the Java Virtual Machine as a no-argument constructor. Constructors call parent constructors through the super keyword and instance members cannot be accessed until after the parent constructor runs.

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106 views1 page

Java Constructors Guide

Constructors are invoked when new objects are created and have the same name as the class. They cannot have a return type or be overridden. Every class has at least one constructor provided either by the programmer or implicitly by the Java Virtual Machine as a no-argument constructor. Constructors call parent constructors through the super keyword and instance members cannot be accessed until after the parent constructor runs.

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aakritich
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Constructor Cheatsheet

 Constructor is invoked when a new object is created.


 Constructor’s can also be overloaded but it can not be overridden.
 Every class has at least one constructor. If user doesn’t provide any JVM will provide a default no arg constructor.
 Abstract class also has constructor.
 Constructor must have the same name as class.
 Constructor can’t have a return type.
 If a method with the same name as class has return type will be treated as normal member method and not
constructor.
 Constructor can have any access modifier(All).
 Default constructor is a no arg constructor which calls the no arg constructor of super class. In case super class
doesn’t have any no arg constructor then it will throw a run time exception.
 In case where a class has default constructor, its super class needs to have a no arg constructor.
 First statement of a constructor can be either this or super but can not be both at the same time.
 If coder doesn’t write any this or super call then compiler will add a call to super.
 Instance member can be accessible only after the super constructor runs.
 Interfaces do not have constructors.
 Constructor are not inherited. Hence can not be overridden.
 Constructor can not be directly invoked. It will be invoked(Implicitly) when a new object is created or a call by other
constructor.

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