How do I make and update method in java?

Question

I need to be able to update the quantity very simply in this section of code:

import java.util.HashMap; import java.util.Map; public class StockData { private static class Item { Item(String n, double p, int q) { name = n; price = p; quantity = q; } // get methods public String getName() { return name; } public double getPrice() { return price; } public int getQuantity() { return quantity; } // instance variables private String name; private double price; private int quantity; } // with a Map you use put to insert a key, value pair // and get(key) to retrieve the value associated with a key // You don't need to understand how this works! private static Map<String, Item> stock = new HashMap<String, Item>(); static { // if you want to have extra stock items, put them in here // use the same style - keys should be Strings stock.put("00", new Item("Bath towel", 5.50, 10)); stock.put("11", new Item("Plebney light", 20.00, 5)); stock.put("22", new Item("Gorilla suit", 30.00, 7)); stock.put("33", new Item("Whizz games console", 50.00, 8)); stock.put("44", new Item("Oven", 200.00, 4)); } public static String getName(String key) { Item item = stock.get(key); if (item == null) return null; // null means no such item else return item.getName(); } public static double getPrice(String key) { Item item = stock.get(key); if (item == null) return -1.0; // negative price means no such item else return item.getPrice(); } public static int getQuantity(String key) { Item item = stock.get(key); if (item == null) return -1; // negative quantity means no such item else return item.getQuantity(); } // update stock levels // extra is +ve if adding stock // extra is -ve if selling stock public static void update(String key, int extra) { Item item = stock.get(key); if (item != null) item.quantity += extra; } }

I've built the GUI for the update page and just need the method to add into it?

Sorry for the trivial question but you have to start somewhere.

Thanks for your help.

so you want that someone help you to write a update method?

Freak
– Freak

2013-03-04 11:13:56 +00:00
Commented Mar 4, 2013 at 11:13 — Freak
– Freak, Commented Mar 4, 2013 at 11:13
What is your question exactly?

Duncan Jones
– Duncan Jones

2013-03-04 11:15:14 +00:00
Commented Mar 4, 2013 at 11:15 — Duncan Jones
– Duncan Jones, Commented Mar 4, 2013 at 11:15

Philipp Otto · Accepted Answer · 2013-03-04 11:18:36Z

1

I don´t know if I really get your problem, but this is my suggestion to increase the quantity of your Item.

Just add a public method like this:

public void addQuantity(int q) { quantity += q }

I hope you meant this.

answered Mar 4, 2013 at 11:18

Philipp Otto

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2 Comments

Sebastiaan van den Broek Over a year ago

Strictly speaking, this doesn't update the quantity but adds to it.

Philipp Otto Over a year ago

You´re right, but I think a method to add the quantity would be more suitable in his case.

Sebastiaan van den Broek · Accepted Answer · 2013-03-04 11:14:51Z

Add this method:

public void setQuantity(int q) { quantity = q }

And you may want to start reading at http://docs.oracle.com/javase/tutorial/

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