1    /* 
2     * Program featuring an array to store and interactively manipulate a list of numbers. 
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 WordsList {
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 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       // 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               String word = scanner.next();
47               words.add(word);
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   
58       private static void interpreter() {
59           System.out.print(">>> ");
60           String command = commandReader.next();
61           if (command.equalsIgnoreCase("DISPLAY")) {
62               interpreterDisplayCommand();
63           } else if (command.equalsIgnoreCase("PRINT")) {
64               interpretPrintCommand();
65           } else if (command.equalsIgnoreCase("SWAP")) {
66               interpretSwapCommand();
67           } else if (command.equalsIgnoreCase("ADD")) {
68               interpretAddCommand();
69           } else if (command.equalsIgnoreCase("HELP")) {
70               interpretHelpCommand();
71           } else if (command.equalsIgnoreCase("EXIT")) {
72               System.exit(0);
73           } else {
74               System.out.println("### Unrecognizable command: " + command);
75           }
76           interpreter();
77       }
78   
79       private static void interpreterDisplayCommand() {
80           displayWords();
81       }
82   
83       private static void interpretPrintCommand() {
84           String operand = commandReader.next();
85           if (operand.equalsIgnoreCase("FIRST")) {
86               System.out.println(words.get(0));
87           } else if (operand.equalsIgnoreCase("LAST")) {
88               System.out.println(words.get(numberOfWords - 1));
89           } else {
90               int index = Integer.valueOf(operand);
91               System.out.println(words.get(index-1));
92           }
93       }
94   
95       private static void interpretHelpCommand() {
96           System.out.println("HELP - display a menu of commands");
97           System.out.println("DISPLAY - display the list of numbers");
98           System.out.println("PRINT - print a number (FIRST;LAST;nth)");
99           System.out.println("SWAP - exchange two elements (nth;mth)");
100          System.out.println("ADD - add a number to the list (FIRST;LAST)");
101          System.out.println("EXIT - terminate execution of the program");
102      }
103  
104      private static void interpretSwapCommand() {
105          int position1 = commandReader.nextInt();
106          int position2 = commandReader.nextInt();
107          String temp = words.get(position1 - 1);
108          words.set(position1 - 1,words.get(position2 - 1));
109          words.set(position2 - 1, temp);
110      }
111  
112      private static void interpretAddCommand() {
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(0, commandReader.next());
130      }
131  }
132