CS1 Standard Demo Page

/*
*Program featuring an array to store and interactively manipulate a list
*of numbers.
*/
package arrayplay;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.Scanner;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
*
*@authorblue
*/
public class NumberList {
// VARIABLES LOCAL TO THE CLASS, AND HENCE GLOBAL TO THE METHODS
private static final int LIMIT = 1000;
private static int[] numbers = new int[LIMIT];
private static int numberOfNumbers = 0;
private static Scanner commandReader = new Scanner(System.in);
/**
     * @param args
*@paramargsthecommandlinearguments
*/
public static void main(String[] args) {
try {
// ESTABLISH THE ARRAY OF NUMBERS                            
readNumbers();
// CHECK THE DATA
   System.out.println("\nThe original list of numbers ...");
   displayNumbers();
// ENTER THE INTERPRETER
interpreter();
}catch (FileNotFoundException ex){
System.out.println("The file was not found. Please think again.");
System.exit(-1);
}
}
// Assuming that the data file will be found in the public_html/data
// subdirectory of the user’s home directory.
private static Scanner establishScanner(String fn) throws FileNotFoundException {
String separator = System.getProperty("file.separator");
String home = System.getProperty("user.home");
String path = home + separator + "CS1Files" + separator + "data" + separator;
String NumberSet = path + fn;
return new Scanner(new File(NumberSet));
}
private static void readNumbers() throws FileNotFoundException {
Scanner scanner = establishScanner("NumberSet");
while ( scanner.hasNext() ) {
numbers[numberOfNumbers] = scanner.nextInt();
numberOfNumbers = numberOfNumbers + 1;
}
}
private static void displayNumbers() {
for ( int x = 0; x < numberOfNumbers;x=x+1){
System.out.println(numbers[x]);
}
}
private static void interpreter() {
System.out.print(">>> ");
String command = commandReader.next();
if ( command.equalsIgnoreCase("DISPLAY") ) {
interpreterDisplayCommand();
} else if(command.equalsIgnoreCase("PRINT")){
interpretPrintCommand();
}else if(command.equalsIgnoreCase("SWAP")){
interpretSwapCommand();
}else if(command.equalsIgnoreCase("ADD")){
interpretAddCommand();
}else if(command.equalsIgnoreCase("HELP")){
interpretHelpCommand();
}else if(command.equalsIgnoreCase("EXIT")){
System.exit(0);
}else{
System.out.println("### Unrecognizable command: " + command);
}
interpreter();
}
private static void interpreterDisplayCommand() {
displayNumbers();
}
private static void interpretPrintCommand() {
String operand = commandReader.next();
if ( operand.equalsIgnoreCase("FIRST") ) {
System.out.println(numbers[0]);
}else if(operand.equalsIgnoreCase("LAST")){
System.out.println(numbers[numberOfNumbers-1]);
}else{
int index = Integer.valueOf(operand);
System.out.println(numbers[index-1]);
}
}
private static void interpretHelpCommand() {
System.out.println("HELP - display a menu of commands");
System.out.println("DISPLAY - display the list of numbers");
System.out.println("PRINT - print a number (FIRST;LAST;nth)");
System.out.println("SWAP - exchange two elements (nth;mth)");
System.out.println("ADD - add a number to the list (FIRST;LAST)");
System.out.println("EXIT - terminate execution of the program");
}
private static void interpretSwapCommand() {
int position1 = commandReader.nextInt();
int position2 = commandReader.nextInt();
int temp = numbers[position1-1];
numbers[position1-1] = numbers[position2-1];
numbers[position2-1] = temp;
}
private static void interpretAddCommand() {
String position = commandReader.next();
if ( position.equalsIgnoreCase("LAST") ) {
addLast();
}else if(position.equalsIgnoreCase("FIRST")){
addFirst();
}else{
System.out.println("### invalid operand for add command");
}
numberOfNumbers = numberOfNumbers + 1;
}
private static void addLast() {
numbers[numberOfNumbers] = commandReader.nextInt();
}
private static void addFirst() {
for ( int x = numberOfNumbers; x > 0
;x=x-1){
numbers[x] = numbers[x-1];
}
numbers[0] = commandReader.nextInt();
}
}