1    /* 
2     program featuring an ArrayList to store and interactively manipulate a list of words. 
3     */
4    
5    package arraylistplay;
6    
7    import java.io.File;
8    import java.io.FileNotFoundException;
9    import java.util.ArrayList;
10   import java.util.Scanner;
11   
12   public class WordList {
13       // variables local to the class and thus global to the method
14       private static String inputFileName = "WordSet.txt";
15       private static ArrayList<String> words = new ArrayList<>();
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 the ArrayList
48           while (scanner.hasNext()) {
49               words.add(scanner.next());
50               // numberOfWords = numberOfWords + 1;
51           }
52       }
53   
54       private static void displayWords() {
55           for (int x = 0; x < words.size(); x = x + 1) {
56               System.out.println(words.get(x));
57           }
58       }
59   
60       private static void interpreter() {
61           System.out.print(">>>");
62           String command = commandReader.next();
63           if (command.equalsIgnoreCase("DISPLAY")) {
64               interpreterDisplayCommand();
65           } else if (command.equalsIgnoreCase("PRINT")) {
66               interpretPrintCommand();
67           } else if (command.equalsIgnoreCase("SWAP")) {
68               interpretSwapCommand();
69           } else if (command.equalsIgnoreCase("ADD")) {
70               interpretAddCommand();
71           } else if (command.equalsIgnoreCase("HELP")) {
72               interpretHelpCommand();
73           } else if (command.equalsIgnoreCase("EXIT")) {
74               System.exit(0);
75           } else {
76               System.out.println("### Unrecognizable command: " + command);
77           }
78           interpreter();
79       }
80   
81       private static void interpreterDisplayCommand() {
82           displayWords();
83       }
84   
85       private static void interpretPrintCommand() {
86           String operand = commandReader.next();
87           if (operand.equalsIgnoreCase("FIRST")) {
88               System.out.println(words.get(0));
89           } else if (operand.equalsIgnoreCase("LAST")) {
90               System.out.println(words.get(words.size()-1));
91           } else {
92               int index = Integer.valueOf(operand);
93               System.out.println(words.get(index-1));
94           }
95       }
96   
97       private static void interpretHelpCommand() {
98           System.out.println("HELP - display a menu of commands");
99           System.out.println("DISPLAY - display the list of numbers");
100          System.out.println("PRINT - print a number (FIRST;LAST;nth)");
101          System.out.println("SWAP - exchange two elements (nth;mth)");
102          System.out.println("ADD - add a number to the list (FIRST;LAST)");
103          System.out.println("EXIT - terminate execution of the program");
104      }
105  
106      private static void interpretSwapCommand() {
107          int position1 = commandReader.nextInt();
108          int position2 = commandReader.nextInt();
109          String temp = words.get(position2-1);
110          words.set(position2 - 1, words.get(position1 - 1));
111          //System.out.println(temp);
112          words.set(position1 - 1, temp);
113      }
114  
115      private static void interpretAddCommand() {
116          String position = commandReader.next();
117          if (position.equalsIgnoreCase("LAST")) {
118              addLast();
119          } else if (position.equalsIgnoreCase("FIRST")) {
120              addFirst();
121          } else {
122              System.out.println("### invalid operand for add command");
123          }
124      }
125  
126      private static void addLast() {
127          words.set(words.size()-1,commandReader.next());
128      }
129  
130      private static void addFirst() {
131          words.add(0,commandReader.next());
132      }
133  }