Lost and Confused

Question

I am trying to understand arrays.
Where do you declare an array?
I understand that an array is basically a container of like items/objects, but how do I fill the container? How do I get the information into the array? If I don't know the information before hand how do I put it in the array? If I have to be specific and put the information in the array then why do I need an array?
If I have a main that works, and I have a class that works how do I add an array to make the application hold more than one item and then print out the multiple items?
In my mind the application should simply use the loop to gather the information then print out the information when the loop reaches it's end.
All the examples I have found basically show the same thing, just the part of the code that declares the array.
What the example do not show is how the declaration applies to an application.
I'm getting nowhere fast, except more confused and frustrated :-(

Answer 1

petes,
You helped me work out a problem before :-) If you are not a teacher, you would make an excellent one!
Turing, I read your link as well!
I don't know why I can't figure this array part out. It all reads like it should be obvious, but I'm going from bad to worse! I went from 12 errors to 1 error to 22 errors!
I'm already late on the assignment, that isn't my main objective now. I want to KNOW what I'm doing wrong. It has to be something I can fix. Something I am just not getting.
//Inventory Program Part 1
//Inventory enters and displays Part information
//for product inventory
*Parts used for testing include Glass Break: part # FG730,
*Motion Detector: part# Aurora, and W/L Contact: part # 5816.
*any quantity for units on hand and unit price is appropriate
*for testing purposes.
import java.util.Scanner;    // program uses class Scanner
import java.text.*;
public class Inventory
private static void Quit()
         System.out.println("Goodbye");
     System.exit (0);
    // main method begins execution of Java application
     public static void main(String args[])
                 // create Scanner to obtain input from command window
        Scanner input = new Scanner(System.in);
     while(true)// starts loop to test name
             System.out.print("\nEnter Part Name (stop to quit):  "); // prompt for name
                   part.setName(input.nextLine());   // get name
          if(part.getName().compareToIgnoreCase("stop") == 0)
                 System.out.println("Stop entered, Thank you");
                 Quit();
                 } //end if
        System.out.print("Enter part number for " + part.getName() + ":  ");  // prompt
                   part.setitemNum(input.nextLine());    // read part number from user
        System.out.print("Enter Units on hand: ");    // prompt
                   part.setunits(input.nextDouble());    // read second number from user
     if(part.getunits() <= 0)
                  System.out.println ("Invalid amount, Units on hand worked must be positive");
                  System.out.print("Please enter actual units on hand: ");
                    part.setunits(input.nextDouble());
                  } //end if
     System.out.print("Enter Unit Price: $ ");    // prompt
                   part.setprice(input.nextDouble());    // read third number from user
     if(part.getprice() <= 0)
                  System.out.println ("Invalid amount, Unit Price must be positive");
                  System.out.print("Please enter actual unit price: $ ");
                       part.setprice(input.nextDouble());
                  } //end if
     String fmtStr = "\n%-7s %-10s %12s %12s %12s\n";
     System.out.printf(fmtStr, "Part #", "Part Name",
           "Units On Hand", "Unit Cost", "Total Cost");
      for(int i = 0; i<5; i++)
         part[] Partarray = new part[5];      // allocates memory for 5 strings
         part[0] = "Glass Break"; // initialize first element
         part[1] = "Motion"; // initialize second element
         part[2] = "Keypad"; // etc.
         part[3] = "W/L Contact";
         part[4] = "Contact";
          System.out.println("Element at index 0: " + part[0]);
          System.out.println("Element at index 1: " + part[1]);
          System.out.println("Element at index 2: " + part[2]);
          System.out.println("Element at index 3: " + part[3]);
          System.out.println("Element at index 4: " + part[4]);
     }//end for
        }//end while
    }//end main
}// end class Inventory
// Class Part holds Part information
class Part
   private String name;
   private String itemNum;
   private double units;
   private double price;
   //default constructor
    public Part()
        name = "";
        itemNum = "";
        units = 0;
         price = 0;
    }//end default constructor
     //Parameterized Constructor
    public Part(String name, String itemNum, double units, double price)
         this.name = name;
         this.itemNum = itemNum;
         this.units = units;
         this.price = price;
    }//end constructor
     public void setName(String name) {
         this.name = name;
        String getName()
            return name;
    public void setitemNum ( String itemNum )
        this.itemNum = itemNum;
    public String getitemNum()
     return itemNum;       }
     public void setunits ( double units )
         this.units = units;
     public double getunits()
          return units;
     public void setprice ( double price )
         this.price = price;
     public double getprice()
     return price;
     public double getvalue()
     return (units * price);
}//end Class PartAnd the original code I started from, which works beautifully......
//Inventory Program Part 1
//Program enters and displays part information
//for product inventory
import java.util.Scanner;    // program uses class Scanner
import java.text.*;
public class Inventory1
private static void Quit()
        System.out.println("Goodbye");
     System.exit (0);
    // main method begins execution of Java application
    public static void main(String args[])
        Part part = new Part();
        // create Scanner to obtain input from command window
        Scanner input = new Scanner(System.in);
     while(true)// starts loop to test name
             System.out.print("Enter Part Name (stop to quit):  "); // prompt for name
                   part.setName(input.nextLine());   // get name
             if(part.getName().compareToIgnoreCase("stop") == 0)
                System.out.println("Stop entered, Thank you");
                Quit();
                } //end if
                System.out.print("Enter part number for " + part.getName() + ":  ");  // prompt
                 part.setitemNum(input.nextLine());    // read part number from user
                 System.out.print("Enter Units on hand: ");    // prompt
                part.setunits(input.nextDouble());    // read second number from user
                         if(part.getunits() <= 0)
                                System.out.println ("Invalid amount, Units on hand worked must be positive");
                                System.out.print("Please enter actual units on hand: ");
                                part.setunits(input.nextDouble());
                           } //end if
          System.out.print("Enter Unit Price: $ ");    // prompt
                part.setprice(input.nextDouble());    // read third number from user
                         if(part.getprice() <= 0)
                                System.out.println ("Invalid amount, Unit Price must be positive");
                                System.out.print("Please enter actual unit price: $ ");
                                part.setprice(input.nextDouble());
                           } //end if
          System.out.printf("\n%s    %s       %.2f    %.2f      %.2f\n", part.getitemNum(), part.getName(), part.getunits(), part.getprice(), part.getvalue());
input.nextLine();
          }//end while
     }// end method main
} // end class Inventory
// Class Part holds Part information
class Part
   private String name;
   private String itemNum;
   private double units;
   private double price;
   //default constructor
    public Part()
        name = "";
        itemNum = "";
        units = 0;
         price = 0;
    }//end default constructor
    //Parameterized Constructor
    public Part(String name, String itemNum, double units, double price)
        this.name = name;
        this.itemNum = itemNum;
        this.units = units;
         this.price = price;
    }//end constructor
     public void setName(String name) {
        this.name = name;
       String getName()
          return name;
    public void setitemNum ( String itemNum )
        this.itemNum = itemNum;
    public String getitemNum()
          return itemNum;
    public void setunits ( double units )
        this.units = units;
    public double getunits()
          return units;
    public void setprice ( double price )
        this.price = price;
    public double getprice()
          return price;
    public double getvalue()
          return (units * price);
}//end Class Part