Class 09-23 Notes CS 107
Friday, September 23, 2011 2:47 PM
Announcements: See updated description posted for program #3
Questions? Last Time: Program swap.java used to swap the value of two variables Today: Parameter scope, overloading, classes intuition
Quiz: A for True, B for False T/F 1. You have to "catch" the same number of parameters that you "throw" T/F 2. The types of parameters must be exactly the same
T/F
3. To share one variable and any changes to it between two methods, you could pass it as a parameter and return any new value using the method return type. 4. To share two variables and any changes to them between two methods, you could pass them as a parameters and return any new values using the method return type. 5. To share multiple variables among methods in a class they must be declared at the top of the class, outside of any methods, but still inside the class.
T/F
T/F
int x = 3;
x,y = addOne( x); x = addTwo( x);
int addOne( int y) { return y+1; }
CS 107 Fall 2011 Page 1
{ return y+1; } int addTwo( int z) { return z+2; }
Scope Think of the scope of methods, which is an issue when parameters in different parts of your program have the same name. "You can look out of a box, but not into a box"
[See other document under today's notes for Confuse.java]
Overloading How similar can two methods Can be? they have the same name? [See the program getNext.java developed in class]
Methods are useful because of: a. Code reuse: write once, reuse many times b. Problem decomposition: allows us to write code one section at a time
Classes and Objects Introduction: What are classes and objects?
A class is an abstract category of things. It is a blueprint or prototype that defines the values (variables) and the actions (methods) common to all objects of a certain kind.
An object is a particular instance of a class. Software objects are often used to model real-world objects you find in everyday life. For example:
CS 107 Fall 2011 Page 2
For example: Object, or Instance Cars The Reed family Chrysler Minivan Songs The Star Spangled-Banner Student Ima Hogg Circle Blue circle in upper-left corner of screen MemorableDate The time my car broke down
Pasted from <https://sites.google.com/site/learnjav/java/objects-and-classes>
Class
Motivation: Think of existing types, like: int x = 3; We have the type as well as actions that can be performed on it (+,-,*,/, output) Now we want to make our own types, along with their own actions. Group together data and actions on that data, to make it easier to reuse code. Let's discuss the concepts involved as we develop the Date example which is presented in our text, in Chapter 4.
CS 107 Fall 2011 Page 3