CSIS 110 – Lecture 27
Last time we looked at some class methods, and what happens when the methods are
called. Our last example looked what happens when the FP are a reference type.
Let's look at Demo3.java
And at PassingReferences.java
All types are passed by value - it does not matter if the type of the formal parameter is a
primitive type or a reference type. This means that if we change the value of a formal
parameter, that change is not reflected back in the calling method.
However,
Let’s look at another example: PassingReferences2.java
So, we can see that method f is working with a distinct JFrame, but method g is working
with the reference that was passed to it.
Repeat KEY POINT:
If we change the value that is referenced by a reference type, that change is reflected
back in the caller. This is a subtle but important distinction!
Instance Methods
Remember, instance methods require an object - we invoke instance methods using an
object's name followed by '.' and the method name.
String s = "Hello";
int l = s.length();
JFrame myFrame = new JFrame( "The Title" );
myFrame.setSize( 200, 300 );
Instance methods are defined without the keyword 'static':
[public] <returnType> <Identifier> ( <Parameter List> ) <MethodBody>
So: class method -- use static
instance method - no static
Let's create a class Point that represents points on a two dimensional grid. Each point has
an x and y coordinate.
What methods do Points need?
