Java: Trouble incrementing static integer for a class

Question

For an assignment, we need to create a simplified BankAccount class with unique IDs for each object created from it. It would seem like the best means to do so would be a static int belonging to the class itself, but attempts to increment it are not increasing its value from 0. What mistake am I making here? I assume it's likely something trivial, but I can't seem to see it.

public class BankAccount {

// instance fields

/**
 * each BankAccount instance should have
 * a unique account number
 */

private int accountNumber;
private String accountHolder;
private double currentBalance;
private double overdraftLimit;

// static fields

private static int nextID;

// constructors

public void BankAccount(){
    this.accountNumber = BankAccount.nextID++;
    this.currentBalance = 0;
    this.overdraftLimit = 0;
}

public void BankAccount(String accountHolder, double overdraftLimit){
    this.accountNumber = BankAccount.nextID++;
    this.currentBalance = 0;
    this.accountHolder = accountHolder;
    this.overdraftLimit = overdraftLimit;
}
}

I defined a main method solely to test the object definition; it's superfluous to the class itself. Any help would be greatly appreciated!

EDIT: For reference, not a duplicate of the other linked issue. This concerns a badly initialised constructor, not a for loop.

Answer 1

It's not the constructors

// this is method: 'bankAccountInstance.BankAccount()' 
public void BankAccount() 
{
    this.accountNumber = BankAccount.nextID++;
    //
}

// and this is method: 'bankAccountInstance.BankAccount("str", 5.1)' 
public void BankAccount(String accountHolder, double overdraftLimit)
{
    this.accountNumber = BankAccount.nextID++;
    //
}  

That are consturctors

// this is constructor 'BankAccount b = new BankAccount()'
public BankAccount() 
{
    this.accountNumber = BankAccount.nextID++;
    //
}

// and this is constructor 'BankAccount b = new BankAccount("Account", 1.0)'
public BankAccount(String accountHolder, double overdraftLimit)
{
    this.accountNumber = BankAccount.nextID++;
    //
}   

You can read more about constructors here

Answer 2

The problem is that what you think you've defined as constructors aren't constructors. They are just methods, and they aren't called ever. So Java inserted a default constructor, and by default it initialized your accountNumber to 0 always.

Change

public void BankAccount(){
public void BankAccount(String accountHolder, double overdraftLimit){

to

public BankAccount(){
public BankAccount(String accountHolder, double overdraftLimit){

Answer 3

Some issues:

• Below are not the constructers.

   public void BankAccount(){ this.accountNumber = BankAccount.nextID++; this.currentBalance = 0; this.overdraftLimit = 0; 

  }

   public void BankAccount(String accountHolder, double overdraftLimit){ this.accountNumber = BankAccount.nextID++; this.currentBalance = 0; this.accountHolder = accountHolder; this.overdraftLimit = overdraftLimit; 

  }

For constructers please follow the below lines :

public BankAccount(){
        this.accountNumber = BankAccount.nextID++;
        this.currentBalance = 0;
        this.overdraftLimit = 0;
    }

• the nextID should be declared as AtomicInteger:

    Integer currentInteger = atomicInteger.get(); Integer nextInteger; do { currentInteger = atomicInteger.get(); nextInteger = currentInteger + 1; } while (atomicInteger.compareAndSet(currentInteger, nextInteger)); 

• it's good to initialize the static variables like below (not mandatory) :

   private static int nextID; static{ nextID=0; } 

• It's good to increment first than assign rather than reverse (not mandatory) .

    this.accountNumber = ++BankAccount.nextID;