1    /* 
2    Program featuring an ArrayList 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<>(1000);
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 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.next());
47               numberOfWords = numberOfWords + 1;
48           }
49       }
50   
51       private static void displayWords() {
52           for (int x=0; x<numberOfWords; x=x+1) {
53               System.out.println(words.get(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               interpreterPrintCommand();
64           } else if (command.equalsIgnoreCase("SWAP")) {
65               interpreterSwapCommand();
66           } else if (command.equalsIgnoreCase("ADD")) {
67               interpreterAddCommand();
68           } else if (command.equalsIgnoreCase("HELP")) {
69               interpreterHelpCommand();
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           displayWords();
80       }
81   
82       private static void interpreterPrintCommand() {
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 interpreterHelpCommand() {
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 interpreterSwapCommand() {
104          int position1 = commandReader.nextInt();
105          int position2 = commandReader.nextInt();
106          String position1Word = words.get(position1-1);
107          String position2Word = words.get(position2-1);
108          words.set(position1-1, position2Word);
109          words.set(position2-1, position1Word);
110      }
111  
112      private static void interpreterAddCommand() {
113          String position = commandReader.next();
114          if (position.equalsIgnoreCase("LAST")) {
115              addLast();
116          } else if (position.equalsIgnoreCase("FIRST")) {
117              addFirst();
118          } else {
119              System.out.println("### invalid operand for add command");
120          }
121          numberOfWords = numberOfWords + 1;
122      }
123  
124      private static void addLast() {
125          words.add(commandReader.next());
126      }
127  
128      private static void addFirst() {
129          words.add(words.get(numberOfWords-1));
130          for (int x = numberOfWords; x > 0; x = x - 1) {
131             words.set(x, words.get(x-1));
132          }
133          words.set(0,commandReader.next());
134      }
135  }
136