1    /* 
2     program featuring an array to store and interactively manipulate a list of words. 
3     */
4    
5    package arrayplay;
6    
7    import java.io.File;
8    import java.io.FileNotFoundException;
9    import java.util.Scanner;
10   
11   public class WordList {
12       // variables local to the class and thus global to the method
13       private static final int LIMIT = 1000;
14       private static String inputFileName = "WordSet.txt";
15       private static String[] words = new String [LIMIT];
16       private static int numberOfWords = 0;
17       private static Scanner commandReader = new Scanner(System.in);
18   
19       public static void main(String[] args) {
20           try {
21               // establish the array of words
22               readWordsFromFile();
23               // check the data
24               System.out.println("The original list of words ...");
25               displayWords();
26               // enter the interpreter
27               interpreter();
28           } catch (FileNotFoundException ex) {
29               System.out.println("The file was not found. Please think again.");
30               System.exit(-1);
31           }
32       }
33   
34       // assuming that the data file will be found in 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 readWordsFromFile() throws FileNotFoundException {
45           // equate a scanner with the input file
46           Scanner scanner = establishScanner(inputFileName);
47           // read the words from the file into an over-sized array
48           String[] temp = new String[LIMIT];
49           int index = 0;
50           while (scanner.hasNext()) {
51               String word = scanner.next();
52               temp[index] = word;
53               index = index + 1;
54           }
55           numberOfWords = index;
56           // transfer the words into a perfectly sized array
57           for (int x = 0; x < numberOfWords; x = x+1) {
58               words[x] = temp[x];
59           }
60       }
61   
62       private static void displayWords() {
63           for (int x = 0; x < numberOfWords; x = x + 1) {
64               System.out.println(words[x]);
65           }
66       }
67   
68       private static void interpreter() {
69           System.out.print(">>>");
70           String command = commandReader.next();
71           if (command.equalsIgnoreCase("DISPLAY")) {
72               interpreterDisplayCommand();
73           } else if (command.equalsIgnoreCase("PRINT")) {
74               interpretPrintCommand();
75           } else if (command.equalsIgnoreCase("SWAP")) {
76              interpretSwapCommand();
77           } else if (command.equalsIgnoreCase("ADD")) {
78               interpretAddCommand();
79           } else if (command.equalsIgnoreCase("HELP")) {
80               interpretHelpCommand();
81           } else if (command.equalsIgnoreCase("EXIT")) {
82               System.exit(0);
83           } else {
84               System.out.println("### Unrecognizable command: " + command);
85           }
86           interpreter();
87       }
88   
89       private static void interpreterDisplayCommand() {
90           displayWords();
91       }
92   
93       private static void interpretPrintCommand() {
94           String operand = commandReader.next();
95           if (operand.equalsIgnoreCase("FIRST")) {
96               System.out.println(words[0]);
97           } else if (operand.equalsIgnoreCase("LAST")) {
98               System.out.println(words[numberOfWords-1]);
99           } else {
100              int index = Integer.valueOf(operand);
101              System.out.println(words[index-1]);
102          }
103      }
104  
105      private static void interpretHelpCommand() {
106          System.out.println("HELP - display a menu of commands");
107          System.out.println("DISPLAY - display the list of numbers");
108          System.out.println("PRINT - print a number (FIRST;LAST;nth)");
109          System.out.println("SWAP - exchange two elements (nth;mth)");
110          System.out.println("ADD - add a number to the list (FIRST;LAST)");
111          System.out.println("EXIT - terminate execution of the program");
112      }
113  
114      private static void interpretSwapCommand() {
115          int position1 = commandReader.nextInt();
116          int position2 = commandReader.nextInt();
117          String temp = words[position1 - 1];
118          words[position1 - 1] = words[position2 - 1];
119          words[position2 - 1] = temp;
120      }
121  
122      private static void interpretAddCommand() {
123          String position = commandReader.next();
124          if (position.equalsIgnoreCase("LAST")) {
125              addLast();
126          } else if (position.equalsIgnoreCase("FIRST")) {
127              addFirst();
128          } else {
129              System.out.println("### invalid operand for add command");
130          }
131          numberOfWords = numberOfWords + 1;
132      }
133  
134      private static void addLast() {
135          words[numberOfWords] = commandReader.next();
136      }
137  
138      private static void addFirst() {
139          for (int x = numberOfWords; x > 0; x = x-1) {
140              words[x] = words[x -1];
141          }
142          words[0] = commandReader.next();
143      }
144  }