1    /* 
2     * Program featuring an ArrayList object to store and manipulate words and character strings. 
3     */
4    package arraylistplay;
5    
6    import java.io.File;
7    import java.io.FileNotFoundException;
8    import java.util.ArrayList;
9    import java.util.Scanner;
10   
11   public class WordList {
12       // VARIABLES LOCAL TO THE CLASS, AND HENCE GLOBAL TO THE METHODS
13       private static final int LIMIT = 1000;
14       private static ArrayList<String> words = new ArrayList<>(LIMIT);
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 WORDS AND CHARACTER STRINGS
21               readWords();
22               // CHECK THE DATA
23               System.out.println("nThe original list of words ...");
24               displayWords();
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       // Assuming that the data file will be found in the public_html/data
34       // subdirectory of the user's home directory.
35       private static Scanner establishScanner(String fn) throws FileNotFoundException {
36           String separator = File.separator;
37           String homeDirectory = System.getProperty("user.home");
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 readWords() throws FileNotFoundException {
44           Scanner scanner = establishScanner("WordSet.txt");
45           while (scanner.hasNext()) {
46               words.add(numberOfWords, scanner.nextLine());
47               numberOfWords = numberOfWords + 1;
48           }
49       }
50   
51       private static void displayWords() {
52           int x = 0;
53           while (x < numberOfWords) {
54               System.out.println(words.get(x));
55               x = x + 1;
56           }
57       }
58   
59       private static void interpreter() {
60           System.out.print(">>> ");
61           String command = commandReader.next();
62           if (command.equalsIgnoreCase("DISPLAY")) {
63               interpreterDisplayCommand();
64           } else if (command.equalsIgnoreCase("PRINT")) {
65               interpretPrintCommand();
66           } else if (command.equalsIgnoreCase("SWAP")) {
67               interpretSwapCommand();
68           } else if (command.equalsIgnoreCase("ADD")) {
69               interpretAddCommand();
70           } else if (command.equalsIgnoreCase("HELP")) {
71               interpretHelpCommand();
72           } else if (command.equalsIgnoreCase("EXIT")) {
73               System.exit(0);
74           } else {
75               System.out.println("### Unrecognizable command: " + command);
76           }
77           interpreter();
78       }
79   
80       private static void interpreterDisplayCommand() {
81           displayWords();
82       }
83   
84       private static void interpretPrintCommand() {
85           String operand = commandReader.next();
86           if (operand.equalsIgnoreCase("FIRST")) {
87               System.out.println(words.get(0));
88           } else if (operand.equalsIgnoreCase("LAST")) {
89               System.out.println(words.get(numberOfWords - 1));
90           } else {
91               int index = Integer.valueOf(operand);
92               System.out.println(words.get(index - 1));
93           }
94       }
95   
96       private static void interpretHelpCommand() {
97           System.out.println("HELP - display a menu of commands");
98           System.out.println("DISPLAY - display the list of words");
99           System.out.println("PRINT - print a word (FIRST;LAST;nth)");
100          System.out.println("SWAP - exchange two elements (nth;mth)");
101          System.out.println("ADD - add a word to the list (FIRST;LAST)");
102          System.out.println("EXIT - terminate execution of the program");
103      }
104  
105      private static void interpretSwapCommand() {
106          int position1 = commandReader.nextInt();
107          int position2 = commandReader.nextInt();
108          String temp = words.get(position1 - 1);
109          words.set(position1 - 1, words.get(position2 - 1));
110          words.set(position2 - 1, temp);
111      }
112  
113      private static void interpretAddCommand() {
114          String position = commandReader.next();
115          if (position.equalsIgnoreCase("LAST")) {
116              addLast();
117          } else if (position.equalsIgnoreCase("FIRST")) {
118              addFirst();
119          } else {
120              System.out.println("### invalid operand for add command");
121          }
122          numberOfWords = numberOfWords + 1;
123      }
124  
125      private static void addLast() {
126          words.add(commandReader.next());
127      }
128  
129      private static void addFirst() {
130          words.add(0, commandReader.next());
131      }
132  }