1    package arraylistplay;
2    
3    import java.io.File;
4    import java.io.FileNotFoundException;
5    import java.util.ArrayList;
6    import java.util.Scanner;
7    
8    public class WordList {
9        // VARIABLES LOCAL TO THE CLASS, AND HENCE GLOBAL TO THE METHODS
10       private static ArrayList<String> Strings = new ArrayList<>();
11       private static Scanner commandReader = new Scanner(System.in);
12   
13       public static void main(String[] args) {
14           try {
15               // ESTABLISH THE ARRAY OF NUMBERS
16               readWords();
17               // CHECK THE DATA
18               System.out.println("nThe original list of numbers ...");
19               displaywords();
20               // ENTER THE INTERPRETER
21               interpreter();
22           } catch (FileNotFoundException ex) {
23               System.out.println("The file was not found. Please think again.");
24               System.exit(-1);
25           }
26       }
27   
28       // Assuming that the data file will be found in the public_html/data
29       // subdirectory of the user’s home directory.
30       private static Scanner establishScanner(String fn) throws FileNotFoundException {
31           String separator = File.separator;
32           String homeDirectory = System.getProperty("user.home");
33           String path = homeDirectory + separator + "public_html" + separator + "data" + separator;
34           String fullFileName = path + fn;
35           return new Scanner(new File(fullFileName));
36       }
37   
38       private static void readWords() throws FileNotFoundException {
39           Scanner scanner = establishScanner("WordSet.txt");
40           while (scanner.hasNext()) {
41              Strings.add(scanner.next());
42           }
43       }
44   
45       private static void displaywords() {
46           for (int x = 0; x < Strings.size(); x = x + 1) {
47               System.out.println(Strings.get(x));
48           }
49       }
50   
51       private static void interpreter() {
52           System.out.print(">>> ");
53           String command = commandReader.next();
54           if (command.equalsIgnoreCase("DISPLAY")) {
55               interpreterDisplayCommand();
56           } else if (command.equalsIgnoreCase("PRINT")) {
57               interpretPrintCommand();
58           } else if (command.equalsIgnoreCase("SWAP")) {
59               interpretSwapCommand();
60           } else if (command.equalsIgnoreCase("ADD")) {
61               interpretAddCommand();
62           } else if (command.equalsIgnoreCase("HELP")) {
63               interpretHelpCommand();
64           } else if (command.equalsIgnoreCase("EXIT")) {
65               System.exit(0);
66           } else {
67               System.out.println("### Unrecognizable command: " + command);
68           }
69           interpreter();
70       }
71   
72       private static void interpreterDisplayCommand() {
73           displaywords();
74       }
75   
76       private static void interpretPrintCommand() {
77           String operand = commandReader.next();
78           if (operand.equalsIgnoreCase("FIRST")) {
79               System.out.println(Strings.get(0));
80           } else if (operand.equalsIgnoreCase("LAST")) {
81               System.out.println(Strings.get(Strings.size() - 1));
82           } else {
83               int index = Integer.valueOf(operand);
84               System.out.println(Strings.get(index - 1));
85           }
86       }
87   
88       private static void interpretHelpCommand() {
89           System.out.println("HELP - display a menu of commands");
90           System.out.println("DISPLAY - display the list of numbers");
91           System.out.println("PRINT - print a number (FIRST;LAST;nth)");
92           System.out.println("SWAP - exchange two elements (nth;mth)");
93           System.out.println("ADD - add a number to the list (FIRST;LAST)");
94           System.out.println("EXIT - terminate execution of the program");
95       }
96   
97       private static void interpretSwapCommand() {
98           int position1 = commandReader.nextInt();
99           int position2 = commandReader.nextInt();
100          String temp = Strings.get(position1 - 1);
101          Strings.set(position1 - 1, Strings.get(position2 - 1));
102          Strings.set(position2 - 1, temp);
103      }
104  
105      private static void interpretAddCommand() {
106          String position = commandReader.next();
107          if (position.equalsIgnoreCase("LAST")) {
108              addLast();
109          } else if (position.equalsIgnoreCase("FIRST")) {
110              addFirst();
111          } else {
112              System.out.println("### invalid operand for add command");
113          }
114      }
115  
116  
117            private static void addLast() {
118                        Strings.add(commandReader.next());
119                    }
120  
121      private static void addFirst() {
122                        Strings.add(0,commandReader.next());
123                    }
124        }
125  
126  
127