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