1    /* 
2     * Program featuring an array to store and interactively manipulate a list of words 
3     */
4    
5    package arraylistplay;
6    
7    import java.io.File;
8    import java.io.FileNotFoundException;
9    import java.util.ArrayList;
10   import java.util.Scanner;
11   
12   public class WordList {
13       // VARIABLES LOCAL TO THE CLASS, AND HENCE GLOBAL TO THE METHODS
14       private static ArrayList<String> words = new ArrayList<>();
15       private static int numberOfWords = 0;
16       private static Scanner commandReader = new Scanner(System.in);
17   
18       public static void main(String[] args) {
19           try {
20               // ESTABLISH THE ARRAY OF NUMBERS
21               readWords();
22               // CHECK THE DATA
23               // System.out.println("nThe original list of numbers ...");
24               // displayNumbers();
25               // ENTER THE INTERPRETER
26               interpreter();
27           } catch (FileNotFoundException ex) {
28               System.out.println("The file was not found. Please think again");
29               System.exit(-1);
30           }
31       }
32   
33   
34       // ASSUMING THAT THE DATA FILE WILL BE FOUND IN THE PUBLIC_HTML/DATA
35       // subdirectory of the user's home directory.
36       private static Scanner establishScanner(String fn) throws FileNotFoundException {
37           String separator = File.separator;
38           String homeDirectory = System.getProperty("user.home");
39           String path = homeDirectory + separator + "public_html" + separator + "data" + separator;
40           String fullFileName = path + fn;
41           return new Scanner(new File(fullFileName));
42       }
43   
44       private static void readWords() throws FileNotFoundException {
45           Scanner scanner = establishScanner("WordSet.txt");
46           while (scanner.hasNext()) {
47               words.add(scanner.next());
48               numberOfWords = numberOfWords + 1;
49   
50           }
51       }
52       private static void displayWords() {
53           for (int x = 0; x < numberOfWords; x = x + 1) {
54               System.out.println(words.get(x));
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("### Unrecognisable command: " + command);
74           }
75           interpreter();
76       }
77   
78       private static void interpreterDisplayCommand() {
79           displayWords();
80       }
81   
82       private static void interpretPrintCommand() {
83           String operand = commandReader.next();
84           if (operand.equalsIgnoreCase("FIRST")) {
85               System.out.println(words.get(0));
86           } else if (operand.equalsIgnoreCase("LAST")) {
87               System.out.println(words.get(numberOfWords - 1));
88           } else {
89               int index = Integer.valueOf(operand);
90               System.out.println(words.get(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 words");
97           System.out.println("PRINT - print a word (FIRST;LAST;nth)");
98           System.out.println("SWAP - exchange two elements (nth;mth)");
99           System.out.println("ADD - add a word 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          String temp = words.get(position1 - 1);
107          words.set(position1 - 1, words.get(position2 - 1));
108          words.set(position2 - 1, temp);
109      }
110  
111      private static void interpretAddCommand() {
112          String position = commandReader.next();
113          if (position.equalsIgnoreCase("LAST")) {
114              addLast();
115          } else if (position.equalsIgnoreCase("FIRST")) {
116              addFirst();
117          } else {
118              System.out.println("### invalid operand for add command");
119          }
120          numberOfWords = numberOfWords + 1;
121      }
122  
123      private static void addLast() {
124          words.add(commandReader.next());
125      }
126  
127      private static void addFirst() {
128          words.add(0, commandReader.next());
129      }
130  }
131