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