Please help I have a problem with the code below it says : Exception in thread “main” java.lang.NullPointerException

import java.util.ArrayList; import java.util.Scanner;

public class AddressBookTest {

ArrayList<AddressBook> ABEntry = new ArrayList<>(100); 

public static void main(String[] args) {

AddressBook ABEntry[] = new AddressBook[100];  System.out.println("***PROGRAM INFORMATION*** \nNAME" +         "->  IS THE NAME OF THE PERSON IN THE ADDRESSBOOK \nADDRESS" +         "->  THE ADDRESS OF THE PERSON \nMOBILE NUMBER" +         "->  THE MOBILE NUMBER OF THE PERSON \nEMAIL ADDRESS" +         "->  THE EMAIL ADDRESS OF THE PERSON");  String input; Scanner in = new Scanner(System.in);  AddressBook details = new AddressBook();  boolean stop = false; do {      System.out.println("\nMain Menu");     System.out.println("1. Add an Entry");     System.out.println("2. Delete an Entry");     System.out.println("3. View All Entries");     System.out.println("4. Update an Entry");     System.out.println("5. Exit");     System.out.print("Please enter Choices from 1 to 5: ");     input =(in.next());        switch (input) {         case "1":               System.out.println("==Adding Entry===");              System.out.print("Name: ");             details.setName(in.next());              System.out.print("Address: ");             details.setAddress(in.next());              System.out.print("Mobile Number: ");             details.setMobileNumber(in.nextInt());              System.out.print("Email Address: ");             details.setEmailAddress(in.next()+ "\n");              ABEntry[AddressBook.getABCount()] = (details);              System.out.println("===Added New Entry===");             break;          case "2":             //not yet coded             //System.out.println("Enter the index of the entry, which you want to delete:");             //AB.remove(in.nextInt());              break;          case "3":             if (AddressBook.getABCount()==0)                 System.out.println("===No Entries===");             else                System.out.println("===Your Entries===");                for (int i =0; i <ABEntry.length; i++){                 System.out.println("Name: " + ABEntry[i].getName() + "\nAddress: " + ABEntry[i].getAddress()+ "\nMobile Number: " + ABEntry[i].getMobileNumber()+"\nEmail Address: " + ABEntry[i].getEmailAddress()+"===================");                  }              break;          case "4":             //System.out.println("Enter the index of the entry, which you want to update:");             //get entry at the given index             //AddressBook entryToUpdate = addressBook.get(in.nextInt());              /*System.out.print("First Name (current: " + entryToUpdate.getName() + "):");             entryToUpdate.setName(in.next());              System.out.print("Address: (current: " + entryToUpdate.getAddress() + "):");             entryToUpdate.setAddress(in.next());              System.out.print("Mobile Number: (current: " + entryToUpdate.getMobileNumber() + "):");             entryToUpdate.setMobileNumber(in.nextInt());              System.out.print("Email Address: (current: " + entryToUpdate.getEmailAddress() + "):");             entryToUpdate.setEmailAddress(in.next());*/              break;          default:             break;     } //execute while stop is false } while (!input.equals("5")); System.out.println("***THANK YOU FOR USING MY PROGRAM...***"); 

} }