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Lecture 4 - Implementing Methods

Lecture 4 - Implementing Methods - Implementing Methods...

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Lecture 4 Implementing methods Implementing Methods Introduction a method is a part of a class, and contains a particular set of instructions; so far all the classes you have written have contained just one method, the main method; normally, a method will perform a single well-defined task. Examples a method could perform to calculate the area of a circle; a method to display a particular message on the screen; a method to convert a temperature from fahrenheit to celsius. Calling a method when we get a method to perform its task we say that we are calling the method; when we call a method, what we are actually doing is telling the program to: – jump to a new place (where the method instructions are stored); – carry out the set of instructions that it finds there; – when it has finished, return and carry on where it left off. Declaring and defining methods program 4.1 prompts the user to enter his or her first name, family name and town; each time the prompt is displayed, it is followed by a message. we have had to type out the two lines that display the confidentiality message three times; instead we could have written a method ; Declaring and defining methods program 4.1 prompts the user to enter his or her first name, family name and town; each time the prompt is displayed, it is followed by a message. we have had to type out the two lines that display the confidentiality message three times; instead we could have written a method ; the body of this method (between the two curly brackets) contains the instructions; the first line, which declares the method, is called the method header . Explanation of words in method header private placing the word private in front of the method name means that the method cannot be accessed by any other class. if you wanted the methods of your class to be used by other classes, you would declare your method as public ; the method above is here purely to "help" the main method of this class, and so we declare it as private ; a private method such as this, which is not accessible to other classes, is often referred to as a helper method. static the meaning of this will not be explained fully until lecture 7; for now, you just need to know is that this method has to be static , because it is going to be called from another method (that is, the main method) that is also static .
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void it is possible for a method to send back some information once it terminates; this particular method does not need to do so; the word void indicates that the method does not send back any information. displayMessage() this is the name that we have chosen to give our method; it is followed by a pair of empty brackets; if we want to send information into a method we list, in these brackets, the types of data that we are going to send in; here, however, we do not have to send in any data, and the brackets are left empty.
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