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.Scanner; 10 11 public class WordList { 12 // VARIABLES LOCAL TO THE CLASS, AND HENCE GLOBAL TO THE METHODS 13 private static final int LIMIT = 1000; 14 private static ArrayList<String> words = new ArrayList<>(LIMIT); 15 private static int numberOfNumbers = 0; 16 private static Scanner commandReader = new Scanner(System.in); 17 18 public static void main(String[] args) { 19 try { 20 // ESTABLISH THE ARRAY OF NUMBERS 21 readNumbers(); 22 // CHECK THE DATA 23 // System.out.println("nThe original list of numbers ..."); 24 // displayNumbers(); 25 // ENTER THE INTERPRETER 26 interpreter(); 27 } catch (FileNotFoundException ex) { 28 System.out.println("The file was not found. Please think again."); 29 System.exit(-1); 30 } 31 } 32 33 // Assuming that the data file will be found in the public_html/data 34 // subdirectory of the user’s home directory. 35 private static Scanner establishScanner(String fn) throws FileNotFoundException { 36 String separator = File.separator; 37 String homeDirectory = System.getProperty("user.home"); 38 String path = homeDirectory + separator + "public_html" + separator + "data" + separator; 39 String fullFileName = path + fn; 40 return new Scanner(new File(fullFileName)); 41 } 42 43 private static void readNumbers() throws FileNotFoundException { 44 Scanner scanner = establishScanner("WordSet.txt"); 45 while (scanner.hasNext()) { 46 words.add(scanner.nextLine()); 47 numberOfNumbers = numberOfNumbers + 1; 48 } 49 } 50 51 private static void displayNumbers() { 52 53 for (int x = 0; x < numberOfNumbers; 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.get(numberOfNumbers-1)); 89 } else { 90 int index = Integer.valueOf(operand); 91 System.out.println(words.get(index-1)); 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(position1-1); 108 words.set(position1-1,words.get(position2-1)); 109 words.set(position2-1,temp); 110 } 111 112 private static void interpretAddCommand() { 113 String position = commandReader.next(); 114 if (position.equalsIgnoreCase("LAST")) { 115 addLast(); 116 } else if (position.equalsIgnoreCase("FIRST")) { 117 addFirst(); 118 } else { 119 System.out.println("### invalid operand for add command"); 120 } 121 numberOfNumbers = numberOfNumbers + 1; 122 } 123 124 private static void addLast() { words.add(commandReader.nextLine()); 125 } 126 127 private static void addFirst() { 128 for (int x = numberOfNumbers; x > 0; x = x - 1) { 129 words.set(x,words.get(x-1)); 130 } 131 words.add(commandReader.nextLine()); 132 } 133 } 134