Basic question to formatting custom error Messages

Question

i needed some help understanding the best practice for this scenario.

I have a custom exception class I created that has 3 child classes.I was overriding the message to fit my need . Now the child classes also need to have a custom message. Can I somehow find a way to leverage using the parent class but with a different format ?

Parent Exception Class

public class customException extends RuntimeException {

String myFormat = " Custom Exception message here , %s, %s";

private String A;

public customException(String A, String message){
this.A= A;
super(message);
}

@Override
public String getMessage() {
return String.Format(myFormat, A, super.getMessage());
}

Child Exception class example

public class childException extends customException {

String myFormat = " ChildException message here , %s, %s";

public customException(String A, String message){
super(A, message);
}

@Override
public String getMessage() {
return super.getMessage();    // find a way to format using the ChildClass myFormat? 
    }

EDIT :

The workaround i had currently looked something like this.

Child Exception class example

public class childException extends customException {

String myFormat = " ChildException message here , %s, %s";

private String A;

public customException(String A, String message){
super(message);  // have another constructor in the Parent exception class
this.A=A;
} 

@Override
public String getMessage() {
return String.Format(myFormat, A, super.getMessage()); 
    }

And to avoid the super.getMessage() above, to print the format of the parent exception as well I was checking on the getMessage() method in the super class to see if the class is an instance of the child class. Not a suitable solution.

@Override
public String getMessage() {
if( this instanceOf childException)
return super.getMessage();
else
return String.Format(myFormat, A, super.getMessage());
}

Answer 1

Why dont you change the return super.getMessage() line in childException class.

Instead of:

@Override
public String getMessage() {
    return   super.getMessage();    // find a way to format using the ChildClass myFormat? 
}

Try:

@Override
public String getMessage() {
  this.myFormat = this.myFormat.append("hello");
  return this.myFormat; // find a way to format using the ChildClass myFormat? 
}