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ArrayIndexOutOfBounds Exception Error When Displaying Reservations After Booking - Java

I'm making a reservation feature for my events, and I can successfully add the attendee, however when I want to display the details for every attendee, it gives me a ArrayIndexOutOfBounds exception error, which I'm not quite sure how to fix.
Main.java
private static Scanner sc = new Scanner(System.in);
private static int eventCreationLimit = 5;
private static Event[] events = new Event[eventCreationLimit];
private static int eventsCreated;
public static void main(String args[]) {
String input;
// Main menu.
do {
System.out.println("\n~ BOOKING SYSTEM ~");
System.out.println("------------------");
System.out.println("A. Schedule an Event");
System.out.println("B. Add an Attendee");
System.out.println("C. View Reservations");
System.out.println("X. Exit\n");
System.out.print("Select an option: ");
input = sc.nextLine();
switch (input.toUpperCase()) {
case "A":
scheduleAnEvent();
break;
case "B":
addAttendee();
break;
case "C":
displayReservations();
break;
case "X":
System.out.println("INFO: You have exited the booking system.");
break;
default:
System.out.println("ERROR: Invalid input!");
}
} while (!input.equalsIgnoreCase("X"));
}
private static void scheduleAnEvent() {
System.out.println("\n~ SCHEDULE A EVENT ~");
System.out.println("--------------------");
System.out.print("Enter the ID: ");
String ID = sc.nextLine();
...
System.out.print("Enter the attendee limit: ");
int attendeeLimit = Integer.parseInt(sc.nextLine());
// Add the new event to the array.
events[eventsCreated++] = new Event(ID, ..., attendeeLimit, attendeeLimit, ...);
for (int i = 0; i < eventsCreated; i++)
// Set the places available for the specific event being created to subtract it later when an attendee is added.
if (ID.equals(events[i].getID()))
// The number of places available left in the event can be displayed by going to "B. View All Events".
events[i].setPlacesAvailable(attendeeLimit);
// Give the user a confirmation message.
System.out.println("\nINFO: Sucessfully created Event: " + ID + ".");
}
private static void addAttendee() {
Event event = null;
boolean result = false;
System.out.println("\n~ ADD AN ATTENDEE ~");
System.out.println("-------------------");
System.out.print("Enter attendee name: ");
String name = sc.nextLine();
System.out.print("Enter attendee phone number: ");
String phone = sc.nextLine();
Attendee a = new Attendee(name, phone);
System.out.print("Enter event ID: ");
String eventID = sc.nextLine();
// Check if the given ID matches an event.
for (int i = 0; i < eventsCreated; i++)
if (events[i].getID().equals(eventID))
event = events[i];
if (event != null) {
if (event.getID().equals(eventID)) {
result = ((Event) event).addAttendee(a);
if (result) {
// If the event has enough room, then add the attendee.
System.out.println("INFO: Attendee successfully added to Event: " + eventID + ".");
displayReservations();
}
else
// If the event is full, then the attendee will not be added.
System.out.println("ERROR: The Event: " + eventID + " is full, the attendee could not be added.");
} else
System.out.println("ERROR: The given ID does not match any existing event.");
} else
System.out.println("ERROR: The event was not found.");
}
private static void displayReservations() {
System.out.println("\n~ RESERVATIONS ~");
System.out.println("----------------");
String pattern = "%-18s %-18s %-22s %-1s\n";
System.out.printf(pattern, "NAME", "PHONE", "EVENT ID", "FEE");
System.out.println("----------------------------------------------------------------");
// Display all reservations for events.
for (int i = 0; i < events[i].getAttendeeCount(); i++)
events[i].displayReservations();
}
Event.java
...
private String ID;
private int attendeeLimit;
private int attendeeCount;
private int placesAvailable;
private Attendee[] a = new Attendee[attendeeCount];
public Demonstration(..., String ID, int placesAvailable, int attendeeLimit, ...) {
this.ID = ID;
this.placesAvailable = placesAvailable;
this.attendeeLimit = attendeeLimit;
}
public String getID() { return this.ID; }
public int getPlacesAvailable() { return this.placesAvailable; }
public int getAttendeeLimit() { return this.attendeeLimit; }
public void setPlacesAvailable(int placesAvailable) { this.placesAvailable = placesAvailable; }
public boolean addAttendee(Attendee at) {
// Proceed to add the attendee if there is enough room.
if (attendeeCount <= placesAvailable) {
attendeeCount++;
// Decrease the number of places available by one.
setPlacesAvailable(placesAvailable - 1);
return true;
}
return false;
}
public void displayReservations() {
System.out.println("ID: " + ID);
if (attendeeCount > 0)
for (int i = 0; i < attendeeCount; i++)
a[i].attendeeDetails();
}
Attendee.java
private String name;
private String phone;
public Attendee(String name, String phone) {
this.name = name;
this.phone = phone;
}
public String getName() { return this.name; }
public String getPhone() { return this.phone; }
public void attendeeDetails() {
System.out.println("Name: " + name);
System.out.println("Phone: " + phone);
}
The above code gives me a ArrayIndexOutOfBoundsException error in the displayReservations() method (a[i].attendeeDetails()) whenever I try to add an attendee to an event.
Problem: How do I display all reservation details for all events? Thank you for your help!
EDIT
The error:
Index 0 out of bounds for length 0.

There are a couple of issues with your code:
You are maintaining an attendeeCount separately than the size of the Attendee[], but in your addAttendee() method, you never actually add the new Attendee to the array
Because Attendee[] is an array, it can't grow larger than the size when first initialized. If you want to use an array, instead of an ArrayList that can grow dynamically, you need to initialize the array to the maximum size: placesAvailable:
So, my recommendation would be to switch from using an array to an ArrayList by importing java.util.Arraylist, changing the declaration of the Attendee[] to an ArrayList, and updating the rest of the Event.java code to use the ArrayList, as well as making sure you add the new Attendee in the addAttendee() method. Finally, you don't need to maintain the attendee count separately, just ask the attendees ArrayList it's current size.
Event.java
...
import java.util.*; //You can import all java.util classes
private String ID;
private int attendeeLimit;
private int placesAvailable;
private List<Attendee> attendees = new ArrayList<>(); //Initialize the attendees ArrayList
public Demonstration(..., String ID, int placesAvailable, int attendeeLimit, ...) {
this.ID = ID;
this.placesAvailable = placesAvailable;
this.attendeeLimit = attendeeLimit;
}
public String getID() { return this.ID; }
public int getPlacesAvailable() { return this.placesAvailable; }
public int getAttendeeLimit() { return this.attendeeLimit; }
public void setPlacesAvailable(int placesAvailable) { this.placesAvailable = placesAvailable; }
public boolean addAttendee(Attendee at) {
// Proceed to add the attendee if there is enough room.
if (attendeeCount <= placesAvailable) {
attendees.add(at); //Make sure you add the new Attendee to the list
// Decrease the number of places available by one.
setPlacesAvailable(placesAvailable - 1);
return true;
}
return false;
}
public void displayReservations() {
System.out.println("ID: " + ID);
int attendeeCount = attendees.size(); //Calculate the number of Attendees
if (attendeeCount > 0)
for (int i = 0; i < attendeeCount; i++)
attendees.get(i).attendeeDetails();
}

attendeCount does not have a value as at the time you creating the Array "a". For what you are trying to achieve, I suggest:
i. Use an Arraylist.
ii. Initialize you array in the constructor to attendeLimit.
If possible, I also suggest you use parameter methods where neccessary.

integer to word conversion in java using map continue question

This is a probable answer of my question in stack overflow.Integer to word conversion
At first I have started with dictionary. Then I came to know it is obsolete. So now I use Map instead of dictionary. My code is work well for number till Millions. But the approach I take here is a naive approach. The main problem of this code is
First: Huge numbers of variable use
2nd: Redundant code block as per program requirement
3rd: Multiple if else statement
I am thinking about this problems
Solution for 2nd problem: using user define function or macros to eliminate redundant code block
Solution for 3rd problem: Using switch case
My code:
public class IntegerEnglish {
public static void main(String args[]){
Scanner in=new Scanner(System.in);
System.out.println("Enter the integer");
int input_number=in.nextInt();
Map<Integer,String> numbers_converter = new HashMap<Integer,String>();
Map<Integer,String> number_place = new HashMap<Integer,String>();
Map<Integer,String> number_2nd = new HashMap<Integer,String>();
numbers_converter.put(0,"Zero");
numbers_converter.put(1,"One");
numbers_converter.put(2,"Two");
numbers_converter.put(3,"Three");
numbers_converter.put(4,"Four");
numbers_converter.put(5,"Five");
numbers_converter.put(6,"Six");
numbers_converter.put(7,"Seven");
numbers_converter.put(8,"Eight");
numbers_converter.put(9,"Nine");
numbers_converter.put(10,"Ten");
numbers_converter.put(11,"Eleven");
numbers_converter.put(12,"Twelve");
numbers_converter.put(13,"Thirteen");
numbers_converter.put(14,"Fourteen ");
numbers_converter.put(15,"Fifteen");
numbers_converter.put(16,"Sixteen");
numbers_converter.put(17,"Seventeen");
numbers_converter.put(18,"Eighteen");
numbers_converter.put(19,"Nineteen");
number_place.put(3,"Hundred");
number_place.put(4,"Thousand");
number_place.put(7,"Million");
number_place.put(11,"Billion");
number_2nd.put(2,"Twenty");
number_2nd.put(3,"Thirty");
number_2nd.put(4,"Forty");
number_2nd.put(5,"Fifty");
number_2nd.put(6,"Sixty");
number_2nd.put(7,"Seventy");
number_2nd.put(8,"Eighty");
number_2nd.put(9,"Ninty");
if(input_number== 0){
System.out.println("zero");
}
else if(input_number>0 && input_number<19){
System.out.println(numbers_converter.get(input_number));
}
else if(input_number>19 && input_number<100){
int rem=input_number%10;
input_number=input_number/10;
System.out.print(number_2nd.get(input_number));
System.out.print(numbers_converter.get(rem));
}
else if(input_number==100){
System.out.println(number_place.get(3));
}
else if(input_number>100 && input_number<1000){
int reminder=input_number%100;
int r1=reminder%10;
int q1=reminder/10;
int quot=input_number/100;
System.out.print(numbers_converter.get(quot) + "hundred");
if(reminder>0 && reminder<20){
System.out.print(numbers_converter.get(reminder));
}
else{
System.out.println(number_2nd.get(q1) + numbers_converter.get(r1));
}
}
else if(input_number==1000){
System.out.println(number_place.get(4));
}
else if(input_number>1000 && input_number<10000){
int rem=input_number%100;
int rem_two=rem%10;
int quotient =rem/10;
input_number=input_number/100;
int thousand=input_number/10;
int hundred = input_number%10;
System.out.print(numbers_converter.get(thousand) + "thousand" + numbers_converter.get(hundred)+ " hundred");
if(rem >0 && rem<20){
System.out.print(numbers_converter.get(rem));
}
else if(rem >19 && rem <100){
System.out.print(number_2nd.get(quotient) + numbers_converter.get(rem_two));
}
}
else if(input_number>10000 && input_number<1000000000){
//Say number 418,229,356
int third_part=input_number%1000;//hold 356
input_number=input_number/1000;//hold 418,229
int sec_part=input_number%1000;//hold 229
input_number=input_number/1000;// hold 418
int rem_m=third_part%100;//hold 56
int rem_m1=rem_m%10;//hold 6
int rem_q=rem_m/10;// hold 5
int q_m=third_part/100;// hold 3
int sec_part_rem=sec_part%100;// hold 29
int sec_part_rem1=sec_part_rem%10;//9
int sec_part_q=sec_part_rem/10;//hold 2
int sec_q=sec_part/100;// hold 2
int input_q=input_number/100;// hold 4
int input_rem=input_number%100;//hold 18
int input_q_q=input_rem/10;//hold 1
int input_rem1=input_rem%10;// hold 8
System.out.print(numbers_converter.get(input_q) + " hundred ");
if(input_rem>0 && input_rem<20){
System.out.print(numbers_converter.get(input_rem)+ " Million ");
}
else{
System.out.print(number_2nd.get(input_q_q) + " " + numbers_converter.get(input_rem1) + " Million ");
}
System.out.print(numbers_converter.get(sec_q) + " hundred ");
if(sec_part_rem >0 && sec_part_rem<20){
System.out.println(numbers_converter.get(sec_part_rem) + " thousand ");
}
else{
System.out.print(number_2nd.get(sec_part_q) + " " + numbers_converter.get(sec_part_rem1) + " thousand ");
}
System.out.print(numbers_converter.get(q_m) + " hundred ");
if(rem_m>0 && rem_m<20){
System.out.print(numbers_converter.get(rem_m));
}
else{
System.out.print(number_2nd.get(rem_q) + " " + numbers_converter.get(rem_m1));
}
}
}
}
Redundant Code Blocks
int rem=input_number%100;
int rem_two=rem%10;
int quotient =rem/10;
input_number=input_number/100;
int thousand=input_number/10;
int hundred = input_number%10;
This type of code block used almost every where. Taking a number divide it with 100 or 1000 to find out the hundred position then then divide it with 10 to find out the tenth position of the number. Finally using %(modular division) to find out the ones position.
How could I include user define function and switch case to minimize the code block.

Instead of storing the results in variables, use a method call:
int remainder100(int aNumber) {
return aNumber % 100;
}
int remainder10(int aNumber) {
return aNumber % 10;
}
...etc.
System.out.println(numbers_converter.get(remainder100(input_number)));
About 3rd problem: I wouldn't use switch ... case, too many cases.
Instead, take advantage that numbering repeats itself every 3 digits. That means the pattern for thousands and millions is the same (and billions, trillions, etc).
To do that, use a loop like this:
ArrayList<String> partialResult = new ArrayList<String>();
int powersOf1000 = 0;
for (int kiloCounter = input_number; kiloCounter > 0; kiloCounter /= 1000) {
partialResult.add(getThousandsMilionsBillionsEtc(powersOf1000++);
partialResult.add(convertThreeDigits(kiloCounter % 1000));
}
Then you can print out the contents of partialResult in reverse order to get the final number.

I'd suggest you break your single main method down into a couple of classes. And if you haven't already create a few unit tests to allow you to easily test / refactor things. You'll find it quicker than starting the app and reading from stdin.
You'll find it easier to deal with the number as a string. Rather than dividing by 10 all the time you just take the last character of the string. You could have a class that does that bit for you, and a separate one that does the convert.
Here's what I came up with, but I'm sure it can be improved. It has a PoppableNumber class which allows the last character of the initial number to be easily retrieved. And the NumberToString class which has a static convert method to perform the conversion.
An example of a test would be
#Test
public void Convert102356Test() {
assertEquals("one hundred and two thousand three hundred and fifty six", NumberToString.convert(102356));
}
And here's the NumberToString class :
import java.util.HashMap;
import java.util.Map;
public class NumberToString {
// billion is enough for an int, obviously need more for long
private static String[] power3 = new String[] {"", "thousand", "million", "billion"};
private static Map<String,String> numbers_below_twenty = new HashMap<String,String>();
private static Map<String,String> number_tens = new HashMap<String,String>();
static {
numbers_below_twenty.put("0","");
numbers_below_twenty.put("1","one");
numbers_below_twenty.put("2","two");
numbers_below_twenty.put("3","three");
numbers_below_twenty.put("4","four");
numbers_below_twenty.put("5","five");
numbers_below_twenty.put("6","six");
numbers_below_twenty.put("7","seven");
numbers_below_twenty.put("8","eight");
numbers_below_twenty.put("9","nine");
numbers_below_twenty.put("10","ten");
numbers_below_twenty.put("11","eleven");
numbers_below_twenty.put("12","twelve");
numbers_below_twenty.put("13","thirteen");
numbers_below_twenty.put("14","fourteen ");
numbers_below_twenty.put("15","fifteen");
numbers_below_twenty.put("16","sixteen");
numbers_below_twenty.put("17","seventeen");
numbers_below_twenty.put("18","eighteen");
numbers_below_twenty.put("19","nineteen");
number_tens.put(null,"");
number_tens.put("","");
number_tens.put("0","");
number_tens.put("2","twenty");
number_tens.put("3","thirty");
number_tens.put("4","forty");
number_tens.put("5","fifty");
number_tens.put("6","sixty");
number_tens.put("7","seventy");
number_tens.put("8","eighty");
number_tens.put("9","ninty");
}
public static String convert(int value) {
if (value == 0) {
return "zero";
}
PoppableNumber number = new PoppableNumber(value);
String result = "";
int power3Count = 0;
while (number.hasMore()) {
String nextPart = convertUnitTenHundred(number.pop(), number.pop(), number.pop());
nextPart = join(nextPart, " ", power3[power3Count++], true);
result = join(nextPart, " ", result);
}
if (number.isNegative()) {
result = join("minus", " ", result);
}
return result;
}
public static String convertUnitTenHundred(String units, String tens, String hundreds) {
String tens_and_units_part = "";
if (numbers_below_twenty.containsKey(tens+units)) {
tens_and_units_part = numbers_below_twenty.get(tens+units);
}
else {
tens_and_units_part = join(number_tens.get(tens), " ", numbers_below_twenty.get(units));
}
String hundred_part = join(numbers_below_twenty.get(hundreds), " ", "hundred", true);
return join(hundred_part, " and ", tens_and_units_part);
}
public static String join(String part1, String sep, String part2) {
return join(part1, sep, part2, false);
}
public static String join(String part1, String sep, String part2, boolean part1Required) {
if (part1 == null || part1.length() == 0) {
return (part1Required) ? "" : part2;
}
if (part2.length() == 0) {
return part1;
}
return part1 + sep + part2;
}
/**
*
* Convert an int to a string, and allow the last character to be taken off the string using pop() method.
*
* e.g.
* 1432
* Will give 2, then 3, then 4, and finally 1 on subsequent calls to pop().
*
* If there is nothing left, pop() will just return an empty string.
*
*/
static class PoppableNumber {
private int original;
private String number;
private int start;
private int next;
PoppableNumber(int value) {
this.original = value;
this.number = String.valueOf(value);
this.next = number.length();
this.start = (value < 0) ? 1 : 0; // allow for minus sign.
}
boolean isNegative() {
return (original < 0);
}
boolean hasMore() {
return (next > start);
}
String pop() {
return hasMore() ? number.substring(--next, next+1) : "";
}
}
}

setters and getters in java

I have two files one is the driver, I'm having a problem with setters. It looks did set the value .
public class Movie {
private String name;
private int minutes;
protected int tomatoScore;
public Movie(String name, int minutes, int tomatoScore)
{
this.name=name;
this.minutes=minutes;
this.tomatoScore=tomatoScore;
}
public String getName() {return name;}
public void setName(String name) {this.name=name;}
public int getMinutes() {return minutes;}
public boolean setMinutes(int minutes) {return minutes>=0;}
public int getTomatoScore() {return tomatoScore;};
public boolean setTomatoScore(int tomatoScore) {return tomatoScore>=0 &&tomatoScore<=100;};
public boolean isFresh() {return tomatoScore>=60;};
public void display()
{
//this.name = name;
//this.minutes = minutes;
//this.tomatoScore =tomatoScore;
System.out.println("Movie: "+ getName());
System.out.println("Length: "+ getMinutes() +"min.");
if(tomatoScore>=60)
{
System.out.println("TomatoScore: Fresh");
}
else
{
System.out.println("TomatoScore: Rotten");
}
}
}
and bellow is the driver file if you notice the setters did do the job that is supposed to do I believe the problem is movie class, if you run the driver to test the program you see if you set the value to the negative the if statement does not function properly.( setMinutes and setTomatoScore are wrong. They do not set the class fields at all)
public class MovieDriver {
public static void main (String [] args){
Movie[] myCollection = new Movie[5];
myCollection[0] = new Movie("Batman The Dark Knight", 152, 94);
myCollection[1] = new Movie("Guardians of the Galaxy", 125, 91);
myCollection[2] = new Movie("The GodFather", 178, 98);
myCollection[3] = new Movie("Suicide Squad", 137, 27);
myCollection[4] = new Movie("Get out", 104, 99);
//TODO
//Initialize the variable below and add it to myCollection at index 4.
//You can pick any movie you wish.
Movie yourMovie;
System.out.println("Here are all the movies in my collection of movies.\n");
for(int i = 0; i < myCollection.length; i++) {
if(myCollection[i] != null)
myCollection[i].display();
}
System.out.println("_______________________________________________");
System.out.println("\nHere are the Fresh movies.");
for(int i = 0; i < myCollection.length; i++) {
if(myCollection[i] != null && myCollection[i].isFresh()) {
System.out.println(myCollection[i].getName() + " is fresh.");
}
}
System.out.println();
System.out.println("Here are the Rotten movies.");
for(Movie movieTmp: myCollection){
if (movieTmp != null && !movieTmp.isFresh())
System.out.println(movieTmp.getName() + " is rotten.");
}
System.out.println("_______________________________________________\n");
Movie harryPotter = new Movie("Harry Potter and the Prisoner of Azkaban", 144, 91);
System.out.println("The movie " + harryPotter.getName() + " was created.\n");
System.out.println("Is " + harryPotter.getName() + " a long movie?");
if(harryPotter.getMinutes() > 120) {
System.out.println("Yes, it is a bit long.\n");
} else {
System.out.println("Nope, that isn't too bad.\n");
}
System.out.println("Can I set the minutes of " + harryPotter.getName() + " to a negative number?");
harryPotter.setMinutes(-5);
if(harryPotter.getMinutes() == -5) {
System.out.println("It worked. The runtime is -5 minutes.\n");
} else {
System.out.println("It did NOT work. Negative runtimes are not allowed.\n");
}
System.out.println("Can I set tomato score of " + harryPotter.getName() + " to a negative number?");
harryPotter.setTomatoScore(-100);
if(harryPotter.getTomatoScore() == -100) {
System.out.println("It worked. The score is -100. This movie is terrible according to the site.\n");
} else {
System.out.println("It did NOT work. Negative scores are not allowed.\n");
}
System.out.println("Can I set tomato score of " + harryPotter.getName() + " to a number greater than 100?");
harryPotter.setTomatoScore(101);
if(harryPotter.getTomatoScore() == 101) {
System.out.println("It worked. The score is 101. Best Harry Potter movie ever!\n");
} else {
System.out.println("It did NOT work. Still the best Harry Potter movie out all the movies though.\n");
}
}
}

Your setMinutes and setTomatoScore methods don't set anything, they just return a boolean. I assume you've forgotten to add this.tomatoScore = tomatoScore for example.

As rzwitserloot mentioned, setter function for minutes and tomatoScore are not setting any thing.This might be the case.
Additional I would like add, I found it is better to use well known IDE for java programming like intellij, netBean, eclipse. They have provide many feature like auto generate setter, getter , constructor. So we can focus more on core logic and this saves our time and reduce possiblity of manual error.
One more point I would like to add,
It is better to use setter in the constructor, so before setting value is we want to perform any input validation,we can have that in setter and can use that even when setting value via constructor.
For an example,
public class Example {
private int x;
public Movie(int x){setMinutes(x);}
public void setX(int x) {
//some validation on input
if(x >= 0){this.x = x;}
public int getX() {return x;}

Looks like you need this:
public boolean setMinutes(int minutes) {
if(minutes >= 0 && minutes < 60) {
//I'm guessing the <60 part here, but whatever,
//this is how you'd set the 100 limit on your setTomatoScore method
this.minutes = minutes;
return true;
}
return false;
}
Make similar corrections for the setTomatoScore

​You need to set something tomatoScore in the state of methods as shown below​​ :
public boolean setTomatoScore(int tomatoScore) {
if (tomatoScore >= 0 && tomatoScore <= 100) {
this.tomatoScore = tomatoScore;
return true;
}
return false;
}

Cannot read text file into array and write to text file again

This my whole code.
I want to make a simple program that will read a
text file and put it to array then write it to the
same text file,
also can add and delete the existing input and my input.
Problem
The delete and writer part seems not working, only blank text file when I run the code
These are the error after I select the exit.
java.lang.NullPointerException at ContactList.writer(ContactList.java:51) at
ContactListDriver.main(ContactListDriver.java:73) at
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at
sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at
java.lang.reflect.Method.invoke(Unknown Source) at
edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:27‌​2)
public class Contact {
//Each contact stores the name, phone number, and email address
private String name;
private String number;
private String email;
public Contact(String name, String number, String email)
{
this.name = name;
this.number = number;
this.email = email;
}
public String getName()
{
return name;
}
public String getNumber()
{
return number;
}
public String getEmail()
{
return email;
}
public void setName(String name)
{
this.name = name;
}
public void setNumber(String number)
{
this.number = number;
}
public void setEmail(String email)
{
this.email = email;
}
}
class for processing the inputs.
import java.io.*;
import java.lang.*;
import java.util.*;
public class ContactList {
public Contact[] myContacts;
public static final int MAX = 100;
private int numContacts;
public ContactList()
{
myContacts = new Contact[MAX];
numContacts = 0;
}
public void addContact(String name, String number, String email)
{
Contact c = new Contact(name, number, email);
myContacts[numContacts] = c;
numContacts++;
}
public void deleteContact(String name)
{
for ( int i = 0; i <= numContacts-1 ; i++){
if( name == myContacts[i].getName())
{
myContacts[i] = null;
break;
}
}
numContacts--;
}
public void writer(){
String x = "MyContacts.txt";
try {
PrintWriter outputs = new PrintWriter(x);
for( int i=0; i < myContacts.length; i++)
{
Contact c = myContacts[i];
if(c!=null){ // check if c is null before writing to file
outputs.println(""+c.getName()+" "+c.getNumber()+" "+c.getName());
outputs.flush();
}
}
outputs.close();
}catch (IOException e) {
e.printStackTrace();
}
catch(NullPointerException ex){
}
}
public void displayContacts()
{
int i;
for(i=0; i < myContacts.length; i++)
{
Contact c = myContacts[i];
if(null != c){
System.out.println("Name: " + c.getName());
System.out.println("Number: " + c.getNumber());
System.out.println("Email: " + c.getEmail());
System.out.println("------------------------------------");
}
}
}
}
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
The Driver....
public class ContactListDriver {
public static void main(String[] args) throws FileNotFoundException
{
ContactList cList = new ContactList();
File in = new File("MyContacts.txt");
Scanner sc = new Scanner(in);
int option;
char again = 'n';
String name = null;
String number = null;
String email = null;
while(sc.hasNext())
{
//read one line from text file
String entry = sc.nextLine();
//System.out.println(entry);
String[] con = entry.split("\\s+");
//System.out.println(con[0] + " " + con[1] + " " + con[2]);
cList.addContact(con[0], con[1], con[2]);
}
Scanner userIn = new Scanner(System.in);
do{
displayOptions();
option = userIn.nextInt();
switch(option)
{
case 1:
System.out.println(" Name > ");
name = userIn.next();
System.out.println(" Number > ");
number = userIn.next();
System.out.println(" Email Address > ");
email = userIn.next();
cList.addContact(name, number, email);
break;
case 2:
//delete contact
System.out.println("Contact Name > ");
name = userIn.next();
cList.deleteContact(name);
break;
case 3:
//display contact
cList.displayContacts();
break;
case 4:
cList.writer();
System.out.println(" are you sure ? press y ");
String x = userIn.next();
again = x.charAt(0);
break;
}
}while( again == 'n' );
}
private static void displayOptions() {
System.out.println("(1) Add");
System.out.println("(2) Delete");
System.out.println("(3) Show Contacts");
System.out.println("(4) Exit");
}
}

One problem I see is:
You have a extra break; statement inside deleteContact(String name) function
and String comparision name == myContacts[i].getName() should be name.equals(myContacts[i].getName())
public void deleteContact(String name)
{
for ( int i = 0; i <= numContacts-1; i++){
if( name.equals( myContacts[i].getName()))// string comparison uses equals();
{
myContacts[i] = null;
numContacts--; // this line should be inside of if condition
break;
}
// break; No need of breaking the loop here
}
}
Another problem is at writer() function
public void writer(){
String x = "MyContacts.txt";
try {
PrintWriter outputs = new PrintWriter(x);
for( int i=0; i < myContacts.length; i++)
{
Contact c = myContacts[i];
if(c!=null){ // check if c is null before writing to file
outputs.println(""+c.getName()+" "+c.getNumber()+" "+c.getName());
outputs.flush();
}
}
outputs.close();
}catch (IOException e) {
e.printStackTrace();
}
catch(NullPointerException ex){ // Or just catch the NPE
}

You have declared and initialized the Contact array of size MAX. but,it seems to be that you haven't initialized the elements though. i.e. c is null in the below code
Contact c = myContacts[i];
outputs.println(""+c.getName()+" "+c.getNumber()+" "+c.getName());
outputs.flush();
myContacts[i] should return a Contact instance. As said by Meno, there are lot of other problems in your code. You have to always cover all the possible scenarios while writing the code.

Most importantly you need to fix the ContactList class. It is inserting new elements into the last index, and deleting at any location using the name.
For example, let's say the ContactList has three elements in it at 0, 1 and 2 indexes. So numContacts is set to 3.
Now ContactList has elements as:
[0]C0, [1]C1, [2]C2, [3]null, ...
Then if the contact at 0 index is deleted (set to null), then numContacts is set to 2.
Now the ContactList has elements as:
[0]null, [1]C1, [2]C2, [3] null, ...
A new insert will be added to the index 2, and it will override the C2 value.
Simplest solution is to use an ArrayList instead of an array.
As others have mentioned there are few more issues to fix, but above is the most important in my opinion.

There are many issues with your code so not easy to say where to begin.
First: Your public void deleteContact(String name)-method is broken. It compares Strings using == instead of equals(). And worse: It creates null pointers mid in your array which will cause problems in your writer()-method.
Second: Why do you use arrays? You should use java.util.ArrayList which offers out-of-the-box implementations for adding, getting and deleting contacts.
Third: If you are missing your text file, you might have overlooked it because of missing path so you don't know where to look for this file. So please add a full path to file name.
Fourth: I would also use scanner.hasNextLine() instead of scanner.hasNext() if you then call scanner.nextLine().
Since you said you are not allowed to use ArrayList you should study its source code especially for removing elements. It does not only nullify the array bucket, but also to shift all following elements one index backwards so you don't have any null gap until the index given by element count. And two breaks in deleteContact()-method are really not necessary.

Java code written but no expected output after running

This is a programming assignment I am working on. It takes a single string input that represents a sequence of transactions and prints total gain/loss in the end.
I have my code written and think it should do what I want...but doesn't. I don't get any kind of output after running the program with the specified input.
The input I'm using is:
buy 100 share(s) at $20 each;buy 20 share(s) at $24 each;buy 200
share(s) at $36 each;sell 150 share(s) at $30 each;buy 50 share(s) at
$25 each;sell 200 share(s) at $35 each;
import java.util.*;
import java.text.*;
public class Stocks {
private int shares;
private int price;
private int temp;
private static int total;
private int finalPrice;
private int finalShares;
private Queue<Stocks> StockList = new LinkedList<Stocks>();
private static NumberFormat nf = NumberFormat.getCurrencyInstance();
public Stocks()
{
shares = 0;
price = 0;
}
public Stocks(int shares, int price)
{
this.shares = shares;
this.price = price;
}
public int getShares()
{
return this.shares;
}
public int getPrice()
{
return this.price;
}
public void setShares(int shares)
{
this.shares = shares;
}
public void setPrice(int price)
{
this.price = price;
}
public void sell() {
int sharesToSell = this.getShares();
int priceToSell = this.getPrice();
while (!StockList.isEmpty()) {
int numShares = StockList.peek().getShares();
int sharePrice = StockList.peek().getPrice();
if (numShares < sharesToSell || numShares == sharesToSell) {
temp = sharesToSell - numShares; // remaining shares to sell
finalShares = sharesToSell - temp; // # shares selling at price
finalPrice = priceToSell - sharePrice; // shares sold at adjusted price
total += (finalPrice * finalShares); // Calculates total price
StockList.remove();
sharesToSell = temp; // Remaining shares needed to be sold # price
}
if (numShares > sharesToSell) {
temp = numShares - sharesToSell; // Remaining shares that were bought
finalPrice = priceToSell - sharePrice; // Shares sold at adjusted price
total += (finalPrice * sharesToSell); // adds to running total
StockList.peek().setShares(temp);
}
}
}
public void buy() {
int numShares = this.getShares();
int priceToBuy = this.getPrice();
Stocks newStock = new Stocks(numShares,priceToBuy);
StockList.add(newStock); // adds stock to list
int temptotal = (numShares * priceToBuy); // decreases running total
total += (-1 * temptotal);
}
public static int getTotal() { // gets total profit (or loss)
return total;
}
// *****MAIN METHOD*****
public static void main(String[] args){
Scanner scan = new Scanner(System.in);
System.out.println("Enter transaction sequence:");
String input = scan.nextLine().trim();
String[] inputArray = new String[50];
String[] inputArray2 = new String[50];
int numShares, sharePrice;
inputArray = input.split(";");
for (String i : inputArray) {
if (i.toUpperCase().contains("BUY")) {
inputArray2 = i.split(" ");
inputArray2[4] = inputArray2[4].substring(1);
try {
numShares = Integer.parseInt(inputArray2[1]);
sharePrice = Integer.parseInt(inputArray2[4]);
Stocks newStock = new Stocks(numShares,sharePrice);
newStock.buy();
} catch (NumberFormatException e) {
System.out.println("Error");
return;
}
}
else if (i.toUpperCase().contains("SELL")) {
inputArray2 = input.split(" ");
inputArray2[4] = inputArray2[4].substring(1);
try {
numShares = Integer.parseInt(inputArray2[1]);
sharePrice = Integer.parseInt(inputArray2[4]);
Stocks newStock = new Stocks(numShares,sharePrice);
newStock.sell();
} catch (NumberFormatException e) {
System.out.println("Error");
return;
}
} else {
System.out.println("Error - input does not contain buy/sell");
}
} System.out.println(nf.format(getTotal()));
}
}

You can clean up your parsing a lot by taking a look at java.util.regex.Matcher and java.util.regex.Pattern. They will let you match input against regular expressions. In addition, you can place parens in the regex to extract certain parts. So in your example, you really only care about three things: the operation(buy or sell), the quantity, and the price.
Here's a small example
String sentence = "john programs 10 times a day";
// here's our regex - each set of parens is a "group"
Pattern pattern = Pattern.compile("([A-Za-z]+) programs ([0-9]+) times a day");
Matcher matcher = pattern.matcher(sentence);
String person = matcher.group(1); // here we get the first group
String number = Integers.parseInt(matcher.group(2)); // here we get the second group
System.out.println("Person: " + person + " Number: " + number);

Looks like the main method is returning immediately when it parses a BUY transaction. You probably intended to put the return statement inside the catch block.