When do I use super

Question

I m currently learning about class inheritance in my Java course and I don t understand when to use the super   call   Edit  I found this example of code where super variable is used   class A       int k   10     class Test extends A       public void m             System out println super k             So I understand that here  you must use super to access the k variable in the super-class  However  in any other case  what does super    do  On its own

User · Answer

super is used to call the constructor  methods and properties of parent class

User · Answer

You could use it to call a superclass s method  such as when you are overriding such a method  super foo   etc  -- this would allow you to keep that functionality and add on to it with whatever else you have in the overriden method

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Super will call your parent method  See  http   leepoint net notes-java oop constructors constructor-super html

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You would use it as the first line of a subclass constructor to call the constructor of its parent class   For example   public class TheSuper      public TheSuper            eatCake             public class TheSub extends TheSuper      public TheSub            super            eatMoreCake              Constructing an instance of TheSub would call both eatCake   and eatMoreCake

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Calling exactly super   is always redundant   It s explicitly doing what would be implicitly done otherwise   That s because if you omit a call to the super constructor  the no-argument super constructor will be invoked automatically anyway   Not to say that it s bad style  some people like being explicit   However  where it becomes useful is when the super constructor takes arguments that you want to pass in from the subclass   public class Animal      private final String noise     protected Animal String noise          this noise   noise           public void makeNoise           System out println noise           public class Pig extends Animal       public Pig            super  Oink

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The first line of your subclass  constructor must be a call to super   to ensure that the constructor of the superclass is called

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When you want the super class constructor to be called - to initialize the fields within it   Take a look at this article for an understanding of when to use it   http   download oracle com javase tutorial java IandI super html

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You may also use the super keyword in the sub class when you want to invoke a method from the parent class when you have overridden it in the subclass   Example   public class CellPhone       public void print             System out println  I m a cellphone             public class TouchPhone extends CellPhone        Override     public void print             super print            System out println  I m a touch screen cellphone              public static void main  strings   args            TouchPhone p   new TouchPhone            p print              Here  the line super print   invokes the print   method of the superclass CellPhone  The output will be   I m a cellphone I m a touch screen cellphone

User · Answer

You call super   to specifically run a constructor of your superclass  Given that a class can have multiple constructors  you can either call a specific constructor using super   or super param param  oder you can let Java handle that and call the standard constructor  Remember that classes that follow a class hierarchy follow the  is-a  relationship

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I just tried it  commenting super    does the same thing without commenting it as  Mark Peters said  package javaapplication6              author sborusu     public class Super Test       Super Test            System out println  This is super class  no object is created            class Super sub extends Super Test      Super sub           super           System out println  This is sub class  object is created              public static void main String args             new Super sub

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From oracle documentation page      If your method overrides one of its superclass s methods  you can invoke the overridden method through the use of the keyword super     You can also use super to refer to a hidden field  although hiding fields is discouraged     Use of super in constructor of subclasses      Invocation of a superclass constructor must be the first line in the subclass constructor    The syntax for calling a superclass constructor is  super        or   super parameter list     With super    the superclass no-argument constructor is called  With super parameter list   the superclass constructor with a matching parameter list is called   Note  If a constructor does not explicitly invoke a superclass constructor  the Java compiler automatically inserts a call to the no-argument constructor of the superclass  If the super class does not have a no-argument constructor  you will get a compile-time error    Related post   Polymorphism vs Overriding vs Overloading

[java] When do I use super()?

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