1    
2    package arrayplay;
3    import java.io.File;
4    import java.io.FileNotFoundException;
5    import java.util.Scanner;
6    public class NumberList
7    {
8        private static final int LIMIT = 1000;
9        private static int[] numbers = new int[LIMIT];
10       private static int numberOfNumbers = 0;
11       private static Scanner commandReader = new Scanner(System.in);
12       public static void main(String[] args)
13       {
14           try
15           {
16               readNumbers();
17               interpreter();
18           }
19           catch (FileNotFoundException ex)
20           {
21               System.out.println("The file was not found. Please think again.");
22               System.exit(-1);
23           }
24       }
25       private static Scanner establishScanner(String fn) throws FileNotFoundException
26       {
27           String separator = File.separator;
28           String homeDirectory = System.getProperty("user.home");
29           String path = homeDirectory + separator + "public_html" + separator + "data" + separator;
30           String fullFileName = path + fn;
31           return new Scanner(new File(fullFileName));
32       }
33       private static void readNumbers() throws FileNotFoundException
34       {
35           Scanner scanner = establishScanner("NumberSet.txt");
36           while (scanner.hasNext())
37           {
38               numbers[numberOfNumbers] = scanner.nextInt();
39               numberOfNumbers = numberOfNumbers + 1;
40           }
41       }
42       private static void displayNumbers()
43       {
44           for (int x = 0; x < numberOfNumbers; x = x + 1)
45           {
46               System.out.println(numbers[x]);
47           }
48       }
49       private static void interpreter()
50       {
51           System.out.print(">>> ");
52           String command = commandReader.next();
53           if (command.equalsIgnoreCase("DISPLAY"))
54           {
55               interpreterDisplayCommand();
56           }
57           else if (command.equalsIgnoreCase("PRINT"))
58           {
59               interpretPrintCommand();
60           }
61           else if (command.equalsIgnoreCase("SWAP"))
62           {
63               interpretSwapCommand();
64           }
65           else if (command.equalsIgnoreCase("ADD"))
66           {
67               interpretAddCommand();
68           }
69           else if (command.equalsIgnoreCase("HELP"))
70           {
71               interpretHelpCommand();
72           }
73           else if (command.equalsIgnoreCase("EXIT"))
74           {
75               System.exit(0);
76           }
77           else
78               {
79               System.out.println("### Unrecognizable command: " + command);
80           }
81           interpreter();
82       }
83       private static void interpreterDisplayCommand()
84       {
85           displayNumbers();
86       }
87       private static void interpretPrintCommand()
88       {
89           String operand = commandReader.next();
90           if (operand.equalsIgnoreCase("FIRST"))
91           {
92               System.out.println(numbers[0]);
93           }
94           else if (operand.equalsIgnoreCase("LAST"))
95           {
96               System.out.println(numbers[numberOfNumbers - 1]);
97           }
98           else
99               {
100              int index = Integer.valueOf(operand);
101              System.out.println(numbers[index - 1]);
102          }
103      }
104      private static void interpretHelpCommand()
105      {
106          System.out.println("HELP - display a menu of commands");
107          System.out.println("DISPLAY - display the list of numbers");
108          System.out.println("PRINT - print a number (FIRST;LAST;nth)");
109          System.out.println("SWAP - exchange two elements (nth;mth)");
110          System.out.println("ADD - add a number to the list (FIRST;LAST)");
111          System.out.println("EXIT - terminate execution of the program");
112      }
113      private static void interpretSwapCommand()
114      {
115          int position1 = commandReader.nextInt();
116          int position2 = commandReader.nextInt();
117          int temp = numbers[position1 - 1];
118          numbers[position1 - 1] = numbers[position2 - 1];
119          numbers[position2 - 1] = temp;
120      }
121      private static void interpretAddCommand()
122      {
123          String position = commandReader.next();
124          if (position.equalsIgnoreCase("LAST"))
125          {
126              addLast();
127          }
128          else if (position.equalsIgnoreCase("FIRST"))
129          {
130              addFirst();
131          }
132          else
133              {
134              System.out.println("### invalid operand for add command");
135          }
136          numberOfNumbers = numberOfNumbers + 1;
137      }
138      private static void addLast()
139      {
140          numbers[numberOfNumbers] = commandReader.nextInt();
141      }
142      private static void addFirst()
143      {
144          for (int x = numberOfNumbers; x > 0; x = x - 1)
145          {
146              numbers[x] = numbers[x - 1];
147          }
148          numbers[0] = commandReader.nextInt();
149      }
150  }
151