java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference

This error occurs when you are trying to invoke the 'toString()' method on a null object reference. The 'toString()' method is used to convert an object to a string representation. However, if the object is null, then there is no object to convert and this error is thrown.

To fix this error, you need to make sure that the object you are calling the 'toString()' method on is not null. You can do this by checking for null before calling the method, like this:

if (object != null) {
String stringRepresentation = object.toString();
// Do something with the string representation
}

Alternatively, you can use the null-safe operator '?' to avoid a NullPointerException like this:

String stringRepresentation = object?.toString();