Thread: How to use constructors and class objects together.

I have an assignment to make a program that will use classes and objects to set up a piggy bank system.
It should have a separate class that contains all of the actual calculations. I've been working on it and will post my progress below.
I know (I think anyway) that I have to use objects in the main class to access the constructors of the second.
This is as far as my understanding goes. I need help figuring out the syntax for doing so.

My main class is just a switch that will tell my other class which calculations need to be made.
There has to be a way to add a penny, nickel, dime, quarter, and to view the total or exit (just the way it was assigned).

The code for my main class so far:

// ********************************************************************************
//
//    PROGRAM: My Savings
//
//    PROGRAMMER:  IkeIII
//    CLASS:       CSC 2623
//    SOURCES:     N/A
//
//    DESCRIPTION: Uses classes to make simulate a piggy bank.
//
// ******************************************************************************** 
 
package mysavings;
 
import java.util.Scanner;//allows inputs
 
public class MySavings {
 
    public static void main(String[] args) {
 
        Scanner input = new Scanner(System.in);
        int choice = input.nextInt();
 
        System.out.print("1. Show total in bank.");
        System.out.print("2. Add a penny.");
        System.out.print("3. Add a nickel.");
        System.out.print("4. Add a dime.");
        System.out.print("5. Add a quarter.");
        System.out.print("6. Take money out of bank.");
        System.out.print("Enter 0 to quit.");
        System.out.print("Enter your choice: ");
 
        while(choice == 0){
            switch(choice){
                case 1: break;
                case 2: break;
                case 3: break;
                case 4: break;
                case 5: break;
                case 6: break;
                default: break;
        }
        }
        //Declare a class object, savings
        PiggyBank obj = new PiggyBank();
 
        //Initialize a class object, savings
        obj.setSavings(0);
 
 
    } //End of main
} // End of test circle

And the code for my sub-class:

 
// ********************************************************************************
//
//    PROGRAM: Piggy Bank (Class)
//
//    PROGRAMMER:  IkeIII
//    CLASS:       CSC 2623
//    SOURCES:     N/A
//
//    DESCRIPTION: Uses classes to make simulate a piggy bank.
//
// ******************************************************************************** 
 
package mysavings;
 
public class PiggyBank {
 
    public double savings;
 
    //Constructor
    public PiggyBank(){
        savings = 0;
    }//End of constructor
    //CONSTRUCTOR With a parameter
    public PiggyBank( double s ) {
        savings = s;
 
    }//End of constructor with a parameter
 
    //METHOD: Set the raius of the circle.
    public void setSavings( double newSavings ) {
        savings = newSavings;
 
        //Display output.
    }//End of setRadius
 
    //METHOD: Get the current of the radius
    public double getSavings() {
        return (savings);}
 
}//End of PiggyBank

--- Update ---

I know how to do most of the main stuff. Even if I haven't corrected some of it above. It's only the stuff dealing with moving between the two classes that has me confused if anyone can explain.

'Moving between two classes'... Do you mean to be able to access stuff from other classes and/or call methods/constructors?
----------------------

If so, you would access them usually by instantating an object of the class you want to access. Like this:

MyClass myobj = new MyClass(); //This is calling the default constructor.

Visit The Java™ Tutorials for tutorials on syntax and other stuff.
For methods, after you've instantiated your object, you can call methods.

myobj.maiMethod(); //Calling a method.

Also some tips: if you aren't limited to adding those classes only, you should make more for yourself, making it easier for somethings. For example, creating seperate classes like a Dime class, Quarter class, etc. and having a method in some other class to add those of type Dime, Quarter etc. and increments a number based on an integer value in the Coin classes.
Good luck!
I hope I gave you some help.

Okay, so I have a lot more written now. I'm still having trouble with the first part accessing the second. I have added the obj to access it, but I keep getting error messages for my variable so I have it initialized in both classes at the moment. I know this won't work, but I got tired of seeing the red lines, lol. It doesn't seem to run my switch statement for some reason. Here is my code to date.

 
package mysavings;
 
import java.util.Scanner;//allows inputs
 
public class MySavings {
 
    public static void main(String[] args) {
 
        System.out.println("1. Show total in bank.");
        System.out.println("2. Add a penny.");
        System.out.println("3. Add a nickel.");
        System.out.println("4. Add a dime.");
        System.out.println("5. Add a quarter.");
        System.out.println("6. Take money out of bank.");
        System.out.println("Enter 0 to quit.");
        System.out.println("Enter your choice: ");
 
        double savings = 0;
 
        PiggyBank obj = new PiggyBank();
 
        Scanner input = new Scanner(System.in);
        int choice = input.nextInt();
 
        while(choice != 0){
            switch(choice){
                case 1: System.out.print(obj.getSavings()); break;
                case 2: obj.addPenny(savings); break;
                case 3: break;
                case 4: break;
                case 5: break;
                case 6: break;
                default: break;
            }//end of switch
        }//end of while
 
    } //End of main
} //End of MySavings

and this is the code I've completely for my other class

 
package mysavings;
 
public class PiggyBank {
 
    public double savings;
 
    //Constructor
    public PiggyBank(){
        savings = 0;
    }//End of constructor
 
    public double addPenny( double savings ) {
        savings = savings + .01;
        return savings;
        //Display output.
    }//End of set
 
    public double addNickel( double savings ) {
        savings = savings + .05;
        return savings;
 
        //Display output.
    }//End of set
 
    public double addDime( double savings ) {
        savings = savings + .1;
        return savings;
 
    }//End of set
 
    public double addQuarter( double savings ) {
        savings = savings + .25;
        return savings;
 
    }//End of set
 
    //METHOD: Get the current of the radius
    public double getSavings() {
        return savings;}
 
}//End of PiggyBank

I only had the "savings" variable declared in the second block of code before, so when I called the objects from the other class within my switch I couldn't use it as the parameter. I put another initialization of the variable in the MySavings class to get rid of the red lines, but now I think there is just more than one variable with that name, which I don't believe will work.