CS1 Standard Demo Page

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package arraylistplay;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Scanner;

/**
 *
 * @author ecuevas
 */
public class WordList {

    /**
     * @param args the command line arguments
     */

    private static ArrayList words = new ArrayList<>();
    private static int numberOfWords = 0;
    private static Scanner commandReader = new Scanner(System.in);

    /**
     * @param args the command line arguments
     */
   
    public static void main(String[] args) {
        try {
            readWords();
            interpreter();
        } catch (FileNotFoundException ex) {
            System.out.println("The file was not found. Please think again.");
            System.exit(-1);
        }
    }

    private static Scanner establishScanner(String fn) throws FileNotFoundException {
        String separator = System.getProperty("file.separator");
        String homeDirectory = System.getProperty("user.home");
        String path = homeDirectory + separator + "CS1Files" + separator + "data" + separator;
        String fullFileName = path + fn;
        return new Scanner(new File(fullFileName));
    }

    private static void readWords() throws FileNotFoundException {
        Scanner scanner = establishScanner("WordSet2.text");
        while (scanner.hasNext()) {
            words.add(numberOfWords,scanner.next());
            numberOfWords = numberOfWords + 1;
        }
    }

    private static void displayWords() {
        for (String word : words) {
            System.out.println(word);
        }
    }

    private static void interpreter() {
        System.out.print(">>>");
        String command = commandReader.next();
        if (command.equalsIgnoreCase("DISPLAY")) {
            interpreterDisplayCommand();
        } else if (command.equalsIgnoreCase("PRINT")) {
            interpreterPrintCommand();
        } else if (command.equalsIgnoreCase("SWAP")) {
            interpreterSwapCommand();
        } else if (command.equalsIgnoreCase("ADD")) {
            interpreterAddCommand();
        } else if (command.equalsIgnoreCase("HELP")) {
            interpreterHelpCommand();
        } else if (command.equalsIgnoreCase("EXIT")) {
            System.exit(0);
        } else {
            System.out.println("### Unrecognizable command: " + command);
        }
        System.out.print("\n");
        interpreter();
    }

    private static void interpreterDisplayCommand() {
        displayWords();
    }

    private static void interpreterPrintCommand() {
        String operand = commandReader.next();
        if (operand.equalsIgnoreCase("FIRST")) {
            System.out.println(words.get(0));
        } else if (operand.equalsIgnoreCase("LAST")) {
            System.out.println(words.get(words.size() - 1));
        } else {
            int index = Integer.valueOf(operand);
            System.out.println(words.get(index-1));
        }
    }

    private static void interpreterSwapCommand() {
        int position1 = commandReader.nextInt();
        int position2 = commandReader.nextInt();
        String temp = words.get(position1);
        words.set(position1,words.get(position2));
        words.set(position2,temp);
    }

    private static void interpreterAddCommand() {
        if(isNumeric()) {
            int index = commandReader.nextInt()-1;
            String nextWord = commandReader.next();
            if (index > numberOfWords) {
                System.out.println("### invalid operand for add command");
            } else {
                words.add(index,nextWord);
            }
        } else{
        }
        String position = commandReader.next();
        if (position.equalsIgnoreCase("Last")) {
            words.add(words.size(), commandReader.next());
        } else if (position.equalsIgnoreCase("FIRST")) {
            words.add(0,commandReader.next());
        } else {
            System.out.println("### invalid operand for add command");
        }
        numberOfWords = numberOfWords + 1;
    }

    private static void interpreterHelpCommand() {
        System.out.println("HELP    - display menu of commands");
        System.out.println("DISPLAY - display the list of numbers");
        System.out.println("PRINT   - print a word (FIRST; LAST; nth)");
        System.out.println("SWAP    - exchange two elements (nth; mth)");
        System.out.println("ADD     - add a word to the list (FIRST; LAST)");
        System.out.println("EXIT    - terminate execution of the program");
        
    }

    private static boolean isNumeric() {
        return commandReader.hasNextInt();
    }

}