Java, confused with Exception(String message)

Question

hi, I am very confused with " exception(String message)".

Why when the above exception is triggered, the "message" will be printed out?? I did not see a function that literally says" System.out.print(message)"? Don't we need to add this function ourselves?? Or did I miss it in Throwable or Exception??

I saw some code, for example:

public class LabyrinthException extends Exception {

/**
* Creates a new exception and defines the message.
*
* @param description the description of the problem.
*/
LabyrinthException(String description) {
super(description);
}

/**
* Creates a new exception caused by another exception and defines the message.
*
* @param description the description of the problem.
* @param cause the cause for this exception.
*/
LabyrinthException(String description, Throwable cause) {
super(description, cause);
}
}

//and:

public final class NoGameFieldException extends LabyrinthException {

private static final String MESSAGE_INVALID_GAME_FIELD =
"The position (%d,%d) is not a valid game field.";

/**
* @param pawnPosX the horizontal position accessed.
* @param pawnPosY the vertical position accessed.
*/
public NoGameFieldException(int pawnPosX, int pawnPosY) {
super(MESSAGE_INVALID_GAME_FIELD.formatted(pawnPosX, pawnPosY));
}
}

//and:

private void validatePosition(int posX, int posY) throws LabyrinthException {
if (0 > posX || 0 > posY || horizontalSize <= posX || verticalSize <= posY) {
throw new NoGameFieldException(posX, posY);
}
}

So it seems that if the function validatePosition triggers the "NoGameFieldException", which is inherited from "LabyrinthException ", then the error message ""The position (%d,%d) is not a valid game field." will be printed out.

My question is why??

I go through java manual, it does not explain why this error message, that is , the thi

Answer 1

validatePosition() method is checked, so there is catch() and catch can print LabyrinthException object

try {
new ExceptionTest()
.validatePosition( 100,100);

} catch (LabyrinthException ex) {
System.out.println( ex); // here
}

println() calls Exception.toString() method
inherited from Throwable

public String toString() {
String s = getClass().getName();
String message = getLocalizedMessage();
return (message != null) ? (s + ": " + message) : s;
}

Throwable has our message from constructor of
NoGameFieldException(...)
where is super(msg)