1    package Arrayplay;
2    
3    import java.io.File;
4    import java.io.FileNotFoundException;
5    import java.util.Scanner;
6    
7    public class NumberList {
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   
13       public static void main(String[] args) {
14           try {
15               // ESTABLISH THE ARRAY OF NUMBERS
16               readNumbers();
17               // CHECK THE DATA
18               // System.out.println("nThe original list of numbers ...");
19               // displayNumbers();
20               // ENTER THE INTERPRETER
21               interpreter();
22           } catch (FileNotFoundException ex) {
23               System.out.println("The file was not found. Please think again.");
24               System.exit(-1);
25           }
26       }
27   
28       // Assuming that the data file will be found in the public_html/data
29       // subdirectory of the user’s home directory.
30       private static Scanner establishScanner(String fn) throws FileNotFoundException {
31           String separator = File.separator;
32           String homeDirectory = System.getProperty("user.home");
33           String path = homeDirectory + separator + "public_html" + separator + "data" + separator;
34           String fullFileName = path + fn;
35           return new Scanner(new File(fullFileName));
36       }
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               interpretPrintCommand();
59           } else if (command.equalsIgnoreCase("SWAP")) {
60               interpretSwapCommand();
61           } else if (command.equalsIgnoreCase("ADD")) {
62               interpretAddCommand();
63           } else if (command.equalsIgnoreCase("HELP")) {
64               interpretHelpCommand();
65           } else if (command.equalsIgnoreCase("EXIT")) {
66               System.exit(0);
67           } else {
68               System.out.println("### Unrecognizable command: " + command);
69           }
70           interpreter();
71       }
72   
73       private static void interpreterDisplayCommand() {
74           displayNumbers();
75       }
76   
77       private static void interpretPrintCommand() {
78           String operand = commandReader.next();
79           if (operand.equalsIgnoreCase("FIRST")) {
80               System.out.println(numbers[0]);
81           } else if (operand.equalsIgnoreCase("LAST")) {
82               System.out.println(numbers[numberOfNumbers - 1]);
83           } else {
84               int index = Integer.valueOf(operand);
85               System.out.println(numbers[index - 1]);
86           }
87       }
88   
89       private static void interpretHelpCommand() {
90           System.out.println("HELP - display a menu of commands");
91           System.out.println("DISPLAY - display the list of numbers");
92           System.out.println("PRINT - print a number (FIRST;LAST;nth)");
93           System.out.println("SWAP - exchange two elements (nth;mth)");
94           System.out.println("ADD - add a number to the list (FIRST;LAST)");
95           System.out.println("EXIT - terminate execution of the program");
96       }
97   
98       private static void interpretSwapCommand() {
99           int position1 = commandReader.nextInt();
100          int position2 = commandReader.nextInt();
101          int temp = numbers[position1 - 1];
102          numbers[position1 - 1] = numbers[position2 - 1];
103          numbers[position2 - 1] = temp;
104      }
105  
106      private static void interpretAddCommand() {
107          String position = commandReader.next();
108          if (position.equalsIgnoreCase("LAST")) {
109              addLast();
110          } else if (position.equalsIgnoreCase("FIRST")) {
111              addFirst();
112          } else {
113              System.out.println("### invalid operand for add command");
114          }
115          numberOfNumbers = numberOfNumbers + 1;
116      }
117  
118      private static void addLast() {
119          numbers[numberOfNumbers] = commandReader.nextInt();
120      }
121  
122      private static void addFirst() {
123          for (int x = numberOfNumbers; x > 0; x = x - 1) {
124              numbers[x] = numbers[x - 1];
125          }
126          numbers[0] = commandReader.nextInt();
127      }
128  }
129  
130