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22.02.04 - Java and C, using Objects

String Class - const char * String Buffer class - const char

Do not create any static methods apart from main Can create other static methods in a class

  • Methods can call other static methods
  • Can pass parameters
  • Like global functions Using static methods, the code is not being executed on a specific object, so not really object oriented

Java Conventions​

Use capital first letter for class names Use lower case first letter for variable names and method/function names With multiple words, capitalise the first letter of subsequent words

Data types in Java​

'char' in Java is a 2 byte number to allow for extended character sets

Objects​

  • Use object references to refer to object
  • Object references act like C struct pointers
  • Need to use new to create the object
  • Assigning one reference to another means 'make it refer to the same object'
  • Passing an object reference into a function, or returning one, means referring to the same object, NOT creating a new one.

String​

  • Do not need to create them
  • using + operator with String objects create a new String - without new
  • Passed around like objects
  • Use StringBuffer object if need to change a strings contents

Auto-boxing and unboxing​

Classes to wrap each of the basic data types Can sometimes treat basic types as if they are objects

Java command line args​

use .length to find the length Array of commands inside args There is no filename as the first argument

Applying Functions​

Expressed as object,function() Means apply the function on the object and pass the parameters