Java - using super to call a method in the parent class

For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))

If you're writing a Java class in which you override a method from the base class, can you still make use of that base class method in your new code? Yes, you can. You want the super call.

Here's an example - I had a base class called Shape which overrides the toString method. And I was then writing a Rectangle class in which I wanted a further enhanced toString method. So here it is - firstly running toString from Shape and then adding some extra text.

public String toString() {

String firstbit = super.toString();        

String result = firstbit + " Rectangle " + width + " by " + height;

return result; 

}

The toString method in Java is defined for all Objects as the method which converts the object into a printable string - so that if you ask for an object to be printed this is how it will be formatted. It's a method that all classes that you write will inherit - either from Object or from other classes if you define inheritance yourself, and it is very often overridden at many levels.
(written 2008-01-10, updated 2008-01-12)

Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles

J710 - Java - Extending Classes and More
  [656] Think about your design even if you don't use full UML - (2006-03-24)
  [831] Comparison of Object Oriented Philosophy - Python, Java, C++, Perl - (2006-08-13)
  [1066] Final, Finally and Finalize - three special words in Java - (2007-02-05)
  [1217] What are factory and singleton classes? - (2007-06-04)
  [1294] An example of Java Inheritance from scratch - (2007-08-00)
  [1538] Teaching Object Oriented Java with Students and Ice Cream - (2008-02-12)
  [1556] Java - a demonstration of inheritance on just one page - (2008-02-26)
  [1819] Calling base class constructors - (2008-10-03)
  [2185] Abstract Classes - Java - (2009-05-16)
  [2434] Abstract classes, Interfaces, PHP and Java - (2009-10-03)
  [2604] Tips for writing a test program (Ruby / Python / Java) - (2010-01-29)
  [2860] What methods are available on this Java object? - (2010-07-08)
  [3047] What is a universal superclass? Java / Perl / Python / Other OO languages - (2010-11-13)
  [4334] Splitting out code into name blocks for clarity and reusability - (2014-11-30)
  [4366] Changing what operators do on objects - a comparison across different programming languages - (2014-12-26)
  [4394] Philosophy behind object design - and how I applied in to a Java example - (2015-01-14)
  [4419] Java Inheritance example - group of classes - step by step - (2015-02-08)
  [4422] Objects - from physical to virtual or abstract - Java - (2015-02-10)

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