What to do when readString() fails and String[] out of bounds ?

Question

Dear Java People,
I have a runtime error message that says:
stan_ch13_page523.InvalidUserInputException: readString() failed. Input data is not a string
java.lang.StringIndexOutOfBoundsException: String index out of range: 0
below is the program
thank you in advance
Norman
import java.io.*;
import java.util.*;
public class FormattedInput
    // Method to read an int value
    public int readInt()
      for(int i = 0; i < 2; i ++)
      if(readToken() == tokenizer.TT_NUMBER)
        return (int)tokenizer.nval;   // value is numeric so return as int
      else
        System.out.println("Incorrect input: " + tokenizer.sval +
           " Re-enter as integer");
        continue;         //retry the read operation
      } // end of for loop
      System.out.println("Five failures reading an int value" + " - program terminated");
      System.exit(1);  // end the program
      return 0;
     public double readDouble() throws InvalidUserInputException
       if(readToken() != tokenizer.TT_NUMBER)
          throw new InvalidUserInputException(" readDouble() failed. " + " Input data not numeric");
       return tokenizer.nval;
     public String readString() throws InvalidUserInputException
       if(readToken() == tokenizer.TT_WORD || ttype == '\"' ||  ttype == '\'')
        return tokenizer.sval;
       else
         throw new InvalidUserInputException(" readString() failed. " + " Input data is not a string");
       //helper method to read the next token
       private int readToken()
         try
           ttype = tokenizer.nextToken();
           return ttype;
         catch(IOException e)
           e.printStackTrace(System.err);
           System.exit(1);
          return 0;
       //object to tokenize input from the standard input stream
       private StreamTokenizer tokenizer = new StreamTokenizer(
                                            new BufferedReader(
                                             new InputStreamReader(System.in)));
       private int ttype;                  //stores the token type code
import java.io.*;
import java.util.*;
public class TryVectorAndSort
     public static void main(String[] args)
    Person aPerson;           // a Person object
    Crowd filmCast = new Crowd();
    //populate the crowd
    for( ; ;)
      aPerson = readPerson();
      if(aPerson == null)
        break;   // if null is obtained we break out of the for loop
      filmCast.add(aPerson);
    int count = filmCast.size();
    System.out.println("You added " + count + (count == 1 ? " person":  " people ") + "to the cast.\n");
    //Show who is in the cast using an iterator
     Iterator myIter = filmCast.iterator();
    //output all elements
    while(myIter.hasNext() )
      System.out.println(myIter.next());
    }//end of main
      //read a person from the keyboard
      static public Person readPerson()
     FormattedInput in = new FormattedInput();
        //read in the first name and remove blanks front and back
        System.out.println("\nEnter first name or ! to end:");
        String firstName = "";
        try
        firstName = in.readString().trim(); //read and trim a string
        catch(InvalidUserInputException e)
        e.printStackTrace(System.err);
        //check for a ! entered. If so we are done
        if(firstName.charAt(0) == '!')
          return null;
        //read the last name also trimming the blanks
        System.out.println("Enter last name:");
        String lastName= "";
        try
          lastName = in.readString().trim(); //read and trim a string
        catch(InvalidUserInputException e)
         e.printStackTrace(System.err);
        return new Person(firstName, lastName);
//when I ran the program the output I received was:
import java.io.StreamTokenizer;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.BufferedReader;
public class InvalidUserInputException extends Exception
   public InvalidUserInputException() { }
      public InvalidUserInputException(String message)
          super(message);
import java.util.*;
class Crowd
  public Crowd()
    //Create default Vector object to hold people
     people = new Vector();
  public Crowd(int numPersons)
    //create Vector object to hold  people with given capacity
     people = new Vector(numPersons);
    //add a person to the crowd
    public boolean add(Person someone)
      return people.add(someone);
     //get the person at the given index
      Person get(int index)
      return (Person)people.get(index);
     //get the numbers of persons in the crowd
      public int size()
        return people.size();
      //get  people store capacity
      public int capacity()
        return people.capacity();
      //get a listIterator for the crowd
      public Iterator iterator()
        return people.iterator();
        //A Vector implements the List interface (that has the static sort() method
        public void sort()
          Collections.sort(people);
      //Person store - only accessible through methods of this class
      private Vector people;
public class Person implements Comparable
  public Person(String firstName, String lastName)
    this.firstName = firstName;
    this.lastName = lastName;
  public String toString()
    return firstName + "  " + lastName;
   //Compare Person objects
    public int compareTo(Object person)
       int result = lastName.compareTo(((Person)person).lastName);
       return result == 0 ? firstName.compareTo(((Person)person).firstName):result;
  private String firstName;
  private String lastName;

Answer 1

Dear Nasch,
ttype is declared in the last line of the FormattedInput class
see below
Norman
import java.io.*;
import java.util.*;
public class FormattedInput
    // Method to read an int value
    public int readInt()
      for(int i = 0; i < 2; i ++)
      if(readToken() == tokenizer.TT_NUMBER)
        return (int)tokenizer.nval;   // value is numeric so return as int
      else
        System.out.println("Incorrect input: " + tokenizer.sval +
           " Re-enter as integer");
        continue;         //retry the read operation
      } // end of for loop
      System.out.println("Five failures reading an int value" + " - program terminated");
      System.exit(1);  // end the program
      return 0;
     public double readDouble() throws InvalidUserInputException
       if(readToken() != tokenizer.TT_NUMBER)
          throw new InvalidUserInputException(" readDouble() failed. " + " Input data not numeric");
       return tokenizer.nval;
     public String readString() throws InvalidUserInputException
       if(readToken() == tokenizer.TT_WORD || ttype == '\"' ||  ttype == '\'')
         System.out.println(tokenizer.sval);
        return tokenizer.sval;
       else
         throw new InvalidUserInputException(" readString() failed. " + " Input data is not a string");
       //helper method to read the next token
       private int readToken()
         try
           ttype = tokenizer.nextToken();
           return ttype;
         catch(IOException e)
           e.printStackTrace(System.err);
           System.exit(1);
          return 0;
       //object to tokenize input from the standard input stream
       private StreamTokenizer tokenizer = new StreamTokenizer(
                                            new BufferedReader(
                                             new InputStreamReader(System.in)));
       private int ttype;                  //stores the token type code
     }