Help with object oriented concepts

Question

I am a senior highschool student and although I know Java syntax, I learned with Pascal and other procedural languages so I have a difficult time thinking in OOP concepts (which I will have to learn for college classes). So for practice I went to my college's website and found an assignment on the intro course to programming: [Here are the assignment instructions.|http://www.cs.gsu.edu/knguyen/teaching/2009/spring/csc2010/proj.pdf]
My question is, how can I make my program illustrate more object oriented concepts?
Links:
ode-help.110mb.com/javaproject.java_

Answer 1

Just a few comments (not necessarily about OO and in no particular order):
It's probably not worth it to make constants for the letter A or the plus sign. Make constants for values people would not understand:
// Ok
public static final int ANSWER_TO_THE_UNIVERSE = 42;'
// Probably overkill
public static final int FORTY_TWO = 42;
Good job on having DecimalFormat as a regular instance variable rather than static (since it is not thread-safe)
Good job initializing your object in a consistent state (via the ctor). Now, make as many variables final as you can. Immutable objects are good:[www.javapractices.com/topic/TopicAction.do?Id=29]
Not sure why you declared repeat() to return the boxed version of boolean, just use a primitive
You have a run() method but are not implementing Runnable. Not that it is required, but usually when I see run(), I think of threading
This is a matter of style, but you don't need to name the arguments in the ctor differently than the instance variables that get assigned. You can very easily say:
// Note that it is final.  Make things immutable when you can.
private final String bar;
public Foo(final String bar) {
   // Note:  I don't need a different name here.  This is purely a matter of personal style.
   this.bar = bar;
Consider a while loop in run() rather than a do-loop. What happens if you get no input the first time around?
Java naming conventions dictate that classes start with a capital letter. Generally, an underscore is not used, camel-case is. So, your class should be JavaProject.
Consider making an object for the arguments that are passed into input. Maybe call it GradeCategory, or whatever.
That new object GradeCategory can have the output() method.
For method names, also follow conventions using camel case. So get_double should be getDouble().
Consider reworking such that you use an array or a collection of GradeCategory. You might want to then have an add method in your JavaProject. The add method should ensure the total weight of grades does not exceed 100%.
You can rework the output method of JavaProject to iterate over your GradeCategory objects, calling their own output() methods. Perhaps it also first checks that the weight of all grades equals 100%.Just a few thoughts.
- Saish