ToString() method in my User defined Exception...How is it getting called ?

Question

CustomException.java
public class CustomException extends Exception
     private int age;
     public CustomException(int age)
     this.age = age;
     public String toString()
     return "this is my exception";
ExceptionTest.java
public class ExceptionTest
     static int age=-1;
     public static void main(String args[]) throws Exception
          if(age<0)
          throw new CustomException(age);
After executing ExceptionTest.java , the result is
Exception in thread "main" this is my exception at ExceptionTest.main(ExceptionTest.java:8)
I am just throwing CustomException , to my knowledge only the constructor should run ?
What i see is message "this is my exception" is within the toString() method - which i never called.
From where is the toString() method getting called ?
Also ,
If I want an object of my class to be thrown as an exception object, what should I do?

Answer 1

Your main method is defined as throwing Exception, so the JVM catches the Exception (since nothing in your code does). And it does the equivalent of e.printStackTrace() which, among other things, outputs the result of toString().