public class CreditCard {
  public String acctNo = "0001 0002 0003 0004";
}

public class TestCreditCard {
  public static void main(String args[]) {
    CreditCard cc = new CreditCard( ); // (1)
    System.out.println("Your account number is " + cc.acctNo); // (2)
  }
}

public class CreditCard {
  private String acctNo = "0001 0002 0003 0004";
}

It throws IllegalAccessException at line (2).

The behavior of JVM is not specified for such cases, it depends on implementation.

It prints account number in spite of private specifier.

It throws ClassNotFoundException at line (1).

JVM will refuse to run TestCreditCard as it uses CreditCard and
it should be recompiled to use newer version of CreditCard.

It throws SecurityException at line (2).