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Special Effects and Game Development in Java(TM) - Methods,classes and references

by Anibal Wainstein

1.3 Methods, classes and references

Note that my review of object oriented programming is adapted to the practical use that I see in it, therefore I will not write about strict object oriented theory.

1.3.1 Methods

A method is a bit of Java code that is executed only when called (in other languages they are the equivalent to functions). It may also contain variable declarations which are only valid within the method. These variables are therefore called local variables. A method is defined by the method header and two brackets "}{":

public void myMethod()

The word public indicates that the method can be called by other classes, void indicates that the method does not return a value when it has finished the execution and "myMethod" is the name of the method. You can put variables within the parenthesis () that must be delivered by the user when calling the method in order for it to work. This particular function do not happen to have any variables. Another example :
public int yourMethod(int a, int b)
    return a;
If the method returns anything then "return" must always be specified. In this particular case the method will return an integer int which is the sum of the variables "a" and "b". The function is called like this:
//We declare the "result" variable
int result;
//"result" will contain 
//the number 3 after the calculation
result = yourMethod(1,2);   
Another example:
private byte anotherMethod(int a)
    return ((byte) a);
Private indicates that method may only be used within the class where it has been defined. In the return part you can also have calculations even if it is not so beautiful but this gives a more compact code (less code). In this example we type cast the integer "a" to a byte and return it. The method is called like this:
//"a" will contain the number 41
byte a = anotherMethod(1234217);
This is by the way the same as:
byte a; 
a = anotherMethod(1234217);

When you convert a 32 bit integer to a byte then only the last 8 bits in the number will be left (the 8 last bits in 1234217 has the value 41). Please note that if you do not specify a returnation object then the method is called a constructor. It must have the same name as the class and it will be called when you create an object of the class. A constructor must always be declared as public:

public myklass(int a)

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