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.List;
10       import java.util.Scanner;
11   
12       public class WordArrayList {
13           // VARIABLES LOCAL TO THE CLASS, AND HENCE GLOBAL TO THE METHODS
14           private static final int LIMIT = 1000;
15           private static List<String> words = new ArrayList<>(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 NUMBERS
22                   readNumbers();
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 + "data" + separator;
40               String fullFileName = path + fn;
41               return new Scanner(new File(fullFileName));
42           }
43   
44           private static void readNumbers() throws FileNotFoundException {
45               Scanner scanner = establishScanner("WordSet.txt");
46               while (scanner.hasNext()) {
47                   String word = scanner.next();
48                   words.add(word);
49               }
50           }
51   
52           private static void displayNumbers() {
53               for (int x = 0; x <words.size() - 1; 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               displayNumbers();
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.size()- 1);
89               } else {
90                   int index = Integer.valueOf(operand);
91                   System.out.println(words.get(index));
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);
108              String temp2 = words.get(position2);
109              words.set(position2, temp);
110              words.set(position1, temp2);
111          }
112  
113          private static void interpretAddCommand() {
114              String position = commandReader.next();
115              if (position.equalsIgnoreCase("LAST")) {
116                  addLast();
117              } else if (position.equalsIgnoreCase("FIRST")) {
118                  addFirst();
119              } else {
120                  System.out.println("### invalid operand for add command");
121              }
122              numberOfWords = numberOfWords + 1;
123          }
124  
125          private static void addLast() {
126              words.add(words.size() - 1, commandReader.next());
127          }
128  
129          private static void addFirst() {
130              words.add(0, commandReader.next());
131          }
132      }