1    /* 
2     * Program featuring an array to store and 
3     * interactively manipulate a list of strings, 
4     * using an ArrayList object. 
5     */
6    
7    package arraylistplay;
8    
9    import java.io.File;
10   import java.io.FileNotFoundException;
11   import java.util.ArrayList;
12   import java.util.Scanner;
13   
14   public class WordList {
15       // VARIABLES LOCAL TO THE CLASS, AND HENCE GLOBAL TO THE METHODS
16       private static ArrayList<String> words = new ArrayList<>();
17       private static Scanner commandReader = new Scanner(System.in);
18   
19       public static void main(String[] args) {
20           try {
21               // ESTABLISH THE ARRAY OF NUMBERS
22               readWords();
23               // CHECK THE DATA
24               // System.out.println("nThe original list of numbers ..."); 
25               // displayNumbers();
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 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 + "CS1Files" + 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           }
49       }
50   
51       private static void displayNumbers() {
52           for (int x = 0; x < words.size(); 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               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("### Unrecognizable command: " + command);
74           }
75           interpreter();
76       }
77   
78       private static void interpreterDisplayCommand() {
79           displayNumbers();
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(words.size() - 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 numbers");
97           System.out.println("PRINT - print a number (FIRST;LAST;nth)");
98           System.out.println("SWAP - exchange two elements (nth;mth)");
99           System.out.println("ADD - add a number 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      }
121  
122      private static void addLast() {
123          words.add(commandReader.next());
124  
125      }
126  
127      private static void addFirst() {
128          for (int x = words.size()-1; x > 0; x = x - 1) {
129              words.set(x, words.get(x-1));
130          }
131          words.set(0, commandReader.next());
132      }
133  }