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