Something

import uk.ac.warwick.dcs.util.io.IO;

public class test
{
    
    public static void main(String[] args)
	{
		double bankBalance;
		double spending;
		
		bankBalance = IO.readdouble("Enter opening balance: ");
		
		while (bankBalance >= -400) {
			spending = IO.readdouble("Enter amount spent: ");	
			bankBalance = bankBalance - spending;
		}
		System.out.println("Warning: your balance is now " + bankBalance + ". Put some money in the bank!");
	}
}