Bank.java

package og11bank;


//import og11bank.Konto;

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author Tobi
 */
public class Bank {

    public Konto testKonto=new Konto();
    
    
    

}

Konto.java

package og11bank;

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
/**
 *
 * @author Tobi
 */
public class Konto {

    private int kontostand;
    private boolean gesperrt = false;

    public int abheben(int betrag) {

        if (gesperrt == true) {

            return -1;

        }
        if (kontostand >= betrag) {

            kontostand = kontostand - betrag;     //kurz: kontostand -= betrag;

            return kontostand;

        } else {
            gesperrt = true;
            return -1;

        }

    }

    public int getKontostand() {
        return kontostand;
    }

    public void setKontostand(int egal) {
        if (egal >= 0) {
            kontostand = egal;
        } else {
            //erschiesseAnwender();
            System.out.println("Der uebergebene Anfangskontostand muss groesser 0 sein!");
        }

    }

    public boolean getGesperrt() {
        return gesperrt;

    }

}

OG11Bank.java

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package og11bank;

/**
 *
 * @author Tobi
 */
public class OG11Bank {

    private static boolean kontoGesperrt(Konto ed4) {

        boolean hack = ed4.getGesperrt();
        
        return hack;
    }

    public static void main(String[] args) {

        Bank bank1saar = new Bank();
        Bank bank2palz = new Bank();

        bank1saar.testKonto.setKontostand(109);
        bank2palz.testKonto.setKontostand(11025);

        int xyz = 0;
        while (xyz != -1) {
            xyz = bank1saar.testKonto.abheben(23);
            System.out.println("Kontostand: " + xyz);
            
              if (kontoGesperrt(bank1saar.testKonto)) {
            System.out.println("Konto ist gesperrt!");
        } else {
            System.out.println("Konto ist NICHT gesperrt.");
        
    
        }

        }

      
    }

}