1    package arrayplay;
2    
3    import java.io.*;
4    import java.util.*;
5    
6    public class NumberList {
7    
8        private static final int LIMIT = 1000;
9        private static int[] numbers = new int[LIMIT];
10       private static int numberOfNumbers = 0;
11       private static Scanner commandReader = new Scanner(System.in);
12   
13       public static void main(String [] args){
14           try{
15               readNumbers();
16               interpreter();
17           } catch (FileNotFoundException ex){
18               System.out.println("The file was not found. Please think again.");
19               System.exit(-1);
20           }
21       }
22   
23       private static Scanner establishScanner(String fn) throws FileNotFoundException{
24           String separator = File.separator;
25           String homeDirectory = System.getProperty("user.home");
26           String path = homeDirectory + separator + "public_html" + separator + "data" + separator;
27           String fullFileName = path + fn;
28           return new Scanner((new File(fullFileName)));
29       }
30   
31       private static void readNumbers() throws FileNotFoundException{
32           Scanner scanner = establishScanner("NumberSet.txt");
33           while(scanner.hasNext()){
34               numbers[numberOfNumbers] = scanner.nextInt();
35               numberOfNumbers = numberOfNumbers + 1;
36           }
37       }
38   
39       private static void displayNumbers(){
40           for(int x = 0; x < numberOfNumbers; x = x + 1){
41               System.out.println(numbers[x]);
42           }
43       }
44   
45       private static void interpreter() {
46           System.out.print(">>> ");
47           String command = commandReader.next();
48           if(command.equalsIgnoreCase("DISPLAY")){
49               interpreterDisplayCommand();
50           } else if (command.equalsIgnoreCase("PRINT")){
51               interpreterPrintCommand();
52           }else if (command.equalsIgnoreCase("SWAP")){
53               interpreterSwapCommand();
54           }else if (command.equalsIgnoreCase("ADD")){
55               interpreterAddCommand();
56           }else if (command.equalsIgnoreCase("HELP")){
57               interpreterHelpCommand();
58           }else if (command.equalsIgnoreCase("EXIT")){
59               System.exit(0);
60           }else {
61               System.out.println("### Unrecognizable command: " + command);
62           }
63           interpreter();
64       }
65   
66       private static void interpreterHelpCommand() {
67           System.out.println("HELP - display a menu of commands");
68           System.out.println("DISPLAY - display the list of numbers");
69           System.out.println("PRINT - print a number (FIRST;LAST;nth");
70           System.out.println("SWAP - excahnge two elements (nth;mth)");
71           System.out.println("ADD - add a number to the lidt (FIRST;LAST");
72           System.out.println("EXIT - terminate execution of the program");
73       }
74   
75       private static void interpreterAddCommand() {
76           String position = commandReader.next();
77           if (position.equalsIgnoreCase("LAST")){
78               addLast();
79           } else if (position.equalsIgnoreCase("FIRST")){
80               addFirst();
81           } else {
82               System.out.println("### invalid operand for add command");
83           }
84           numberOfNumbers = numberOfNumbers + 1;
85       }
86   
87       private static void addFirst() {
88           for (int x = numberOfNumbers; x > 0; x = x - 1){
89               numbers[x] = numbers[x - 1];
90           }
91           numbers[0] = commandReader.nextInt();
92       }
93   
94       private static void addLast() {
95           numbers[numberOfNumbers] = commandReader.nextInt();
96       }
97   
98       private static void interpreterSwapCommand() {
99           int position1 = commandReader.nextInt();
100          int position2 = commandReader.nextInt();
101          int temp = numbers[position1 - 1];
102          numbers[position1 - 1] = numbers[position2 - 1];
103          numbers[position2 - 1] = temp;
104      }
105  
106      private static void interpreterPrintCommand() {
107          String operand = commandReader.next();
108          if (operand.equalsIgnoreCase("FIRST")){
109              System.out.println(numbers[0]);
110          } else if (operand.equalsIgnoreCase("LAST")){
111              System.out.println(numbers[numberOfNumbers - 1]);
112          } else {
113              int index = Integer.valueOf(operand);
114              System.out.println(numbers[index - 1]);
115          }
116      }
117  
118      private static void interpreterDisplayCommand() {
119          displayNumbers();
120      }
121  
122  
123  }
124