Classes - Building Java Programs: A Back to Basics Approach - page 542

10 public Stock(String theSymbol) {
11 if (theSymbol == null) {
12 throw new NullPointerException();
13 }
14
15 symbol = theSymbol;
16 totalShares = 0;
17 totalCost = 0.0;
18 }
19
20 // returns the total profit or loss earned on this stock,
21 // based on the given price per share
22 // pre: currentPrice >= 0.0
23 public double getProfit( double currentPrice) {
24 if (currentPrice < 0.0) {
25 throw new IllegalArgumentException();
26 }
27
28 double marketValue = totalShares * currentPrice;
29 return marketValue - totalCost;
30 }
31
32 // records purchase of the given shares at the given price
33 // pre: shares >= 0 && pricePerShare >= 0.0
34 public void purchase( int shares, double pricePerShare) {
35 if (shares < 0 || pricePerShare < 0.0) {
36 throw new IllegalArgumentException();
37 }
38
39 totalShares += shares;
40 totalCost += shares * pricePerShare;
41 }
42 }
Here's the client code to use the Stock class:
1 // This program tracks the user's purchases of two stocks,
2 // computing and reporting which stock was more profitable.
3
4 import java.util.*;
5
6 public class StockMain {
7 public static void main(String[] args) {
8 Scanner console = new Scanner(System.in);