1    /* 
2     * Program featuring an array to store and interactively manipulate a list of numbers. 
3     */
4    package arrayplay;
5    import java.io.File;
6    import java.io.FileNotFoundException;
7    import java.util.Scanner;
8    public class NumberList {
9        // VARIABLES LOCAL TO THE CLASS, AND HENCE GLOBAL TO THE METHODS
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       public static void main(String[] args) {
15           try {
16               // ESTABLISH THE ARRAY OF NUMBERS
17               readNumbers();
18               // CHECK THE DATA
19               // System.out.println("nThe original list of numbers ...");
20               // displayNumbers();
21               // ENTER THE INTERPRETER
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       // 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 + "IdeaProjects" + separator + "CSC-212" + separator + "src" + separator;
34           String fullFileName = path + fn;
35           return new Scanner(new File(fullFileName));
36       }
37       private static void readNumbers() throws FileNotFoundException {
38           Scanner scanner = establishScanner("NumberSet");
39           while (scanner.hasNext()) {
40               numbers[numberOfNumbers] = scanner.nextInt();
41               numberOfNumbers = numberOfNumbers + 1;
42           }
43       }
44       private static void displayNumbers() {
45           for (int x = 0; x < numberOfNumbers; x = x + 1) {
46               System.out.println(numbers[x]);
47           }
48       }
49       private static void interpreter() {
50           System.out.print(">>> ");
51           String command = commandReader.next();
52           if (command.equalsIgnoreCase("DISPLAY")) {
53               interpreterDisplayCommand();
54           } else if (command.equalsIgnoreCase("PRINT")) {
55               interpretPrintCommand();
56           } else if (command.equalsIgnoreCase("SWAP")) {
57               interpretSwapCommand();
58           } else if (command.equalsIgnoreCase("ADD")) {
59               interpretAddCommand();
60           } else if (command.equalsIgnoreCase("HELP")) {
61               interpretHelpCommand();
62           } else if (command.equalsIgnoreCase("EXIT")) {
63               System.exit(0);
64           } else {
65               System.out.println("### Unrecognizable command: " + command);
66           }
67           interpreter();
68       }
69       private static void interpreterDisplayCommand() {
70           displayNumbers();
71       }
72       private static void interpretPrintCommand() {
73           String operand = commandReader.next();
74           if (operand.equalsIgnoreCase("FIRST")) {
75               System.out.println(numbers[0]);
76           } else if (operand.equalsIgnoreCase("LAST")) {
77               System.out.println(numbers[numberOfNumbers - 1]);
78           } else {
79               int index = Integer.valueOf(operand);
80               System.out.println(numbers[index - 1]);
81           }
82       }
83       private static void interpretHelpCommand() {
84           System.out.println("HELP - display a menu of commands");
85           System.out.println("DISPLAY - display the list of numbers");
86           System.out.println("PRINT - print a number (FIRST;LAST;nth)");
87           System.out.println("SWAP - exchange two elements (nth;mth)");
88           System.out.println("ADD - add a number to the list (FIRST;LAST)");
89           System.out.println("EXIT - terminate execution of the program");
90       }
91       private static void interpretSwapCommand() {
92           int position1 = commandReader.nextInt();
93           int position2 = commandReader.nextInt();
94           int temp = numbers[position1 - 1];
95           numbers[position1 - 1] = numbers[position2 - 1];
96           numbers[position2 - 1] = temp;
97       }
98       private static void interpretAddCommand() {
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      private static void addLast() {
110          numbers[numberOfNumbers] = commandReader.nextInt();
111      }
112      private static void addFirst() {
113          for (int x = numberOfNumbers; x > 0; x = x - 1) {
114              numbers[x] = numbers[x - 1];
115          }
116          numbers[0] = commandReader.nextInt();
117      }
118  }