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PONullPointerException when trying to get input for a serializable object
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copied!<p>I have 3 classes: Main, ContactLibrary, and ContactInfo. ContactLibrary contains an ArrayList called myPhoneBook. ContactInfo is made up of a bunch of strings containing name, address, etc.</p> <p>The user wants to search for a name, for example, or anything involving input. The input is done from within the ContactLibrary and ContactInfo classes--both serializable objects.</p> <p>I get a NPE error when it hits that point, however.</p> <pre><code>You have 3 entry(s) saved to disc. Hello, and welcome to Team 6's contact list. What would you like to do? Enter the corresponding number of choice. 1: Add an entry to the contact list. 2: Print the entire contact list. 3: Search for a contact. 4: Exit the program. Please enter a number from 1-4. 3 What would you like to search by? Exception in thread "main" java.lang.NullPointerException at ContactLibrary.searchByCriteria(ContactLibrary.java:62) at Main.optionsPrompt(Main.java:62) at Main.main(Main.java:25) 1: Last Names. 2: Emails. 3: Zip codes. </code></pre> <p>What am I to do?</p> <p>Here is my Main: <a href="http://ideone.com/uvfK4U" rel="nofollow">http://ideone.com/uvfK4U</a> (Contains the other two classes in the top comments) Here is a UML diagram: <a href="http://imgur.com/9W3TS" rel="nofollow">http://imgur.com/9W3TS</a></p> <p>The ContactLibrary class, as requested:</p> <pre><code>/** * ContactLibrary, when constructed, creates an ArrayList of ContactLibrary * references called myPhoneBook. Every index is made to fill in objects * of ContactInfo, which contains entries and credentials. * * Contains methods to create a new entry, search and print by criteria, and print list. */ import java.util.*; public class ContactLibrary implements java.io.Serializable { private static final long serialVersionUID = 1L; private ArrayList<ContactInfo> myPhoneBook; private Scanner libraryInput = new Scanner(System.in); /** Constructs the ArrayList that will hold references to ContactInfo. */ public ContactLibrary() { myPhoneBook = new ArrayList<ContactInfo>(); } /** * Adds an entry to the ArrayList and utilizes the set methods in * ContactInfo. */ public void addEntry() { int doAgain = 1; do { myPhoneBook.add(new ContactInfo()); System.out.println("Would you like to enter another contact?"); System.out.println("1: Yes."); System.out.println("2: No."); doAgain = libraryInput.nextInt(); } while (doAgain == 1); } /** * Goes through every index in myPhoneBook and runs ArrayList.get() on them. */ public void printList() { for (int i = 0; i < myPhoneBook.size(); i++) { System.out.println(myPhoneBook.get(i)); } } /** Counts the number of objects within myPhoneBook and returns a string. */ public String scanDisc() { int entryCount = myPhoneBook.size(); return "You have " + entryCount + " entry(s) saved to disc.\n"; } /** * The prompt for having the user search the database via criteria. Asks the * user to enter in their search criteria. */ public void searchByCriteria() { String criteria; //libraryInput = new Scanner("System.in"); int subSubMenuChoice = 0; System.out.println("What would you like to search by?"); System.out.println("1: Last Names."); System.out.println("2: Emails."); System.out.println("3: Zip codes."); subSubMenuChoice = libraryInput.nextInt(); switch (subSubMenuChoice) { case 1: System.out .println("Please enter the last name you'd like to search for:"); criteria = libraryInput.next(); searchByLastName(criteria); break; case 2: System.out .println("Please enter the e-mail you'd like to search for:"); criteria = libraryInput.next(); searchByEmail(criteria); break; case 3: System.out .println("Please enter the zip code you'd like to search for:"); criteria = libraryInput.next(); searchByZip(criteria); break; default: System.out.println("Exiting"); break; } } /** * Loops through every element in the array and returns a toString of that * index for comparing with the search criteria via contains(). */ public void searchByEmail(String criteria) { for (int i = 0; i < myPhoneBook.size(); i++) { if (criteria.compareTo((myPhoneBook.get(i)).getEmail()) == 0) { System.out.println(myPhoneBook.get(i)); } else { System.out.print(""); } } } /** * Loops through every element in the array and returns a toString of that * index for comparing with the search criteria via contains(). */ public void searchByLastName(String criteria) { for (int i = 0; i < myPhoneBook.size(); i++) { if (criteria.compareTo((myPhoneBook.get(i)).getLastName()) == 0) { System.out.println(myPhoneBook.get(i)); } else { System.out.print(""); } } } /** * Loops through every element in the array and returns a toString of that * index for comparing with the search criteria via contains(). */ public void searchByZip(String criteria) { for (int i = 0; i < myPhoneBook.size(); i++) { if (criteria.compareTo((myPhoneBook.get(i)).getZipcode()) == 0) { System.out.println(myPhoneBook.get(i)); } else { System.out.print(""); } } } /** Reorganizes the array in order by last name. */ public void sortData() { Collections.sort(myPhoneBook); } } </code></pre>

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