#9 error-handling + exceptions + generics

Question 1

how to exit the program if an error occurred

Answer 1

if(condition indicating error){
system.err.println (“Goodbye Cruel JVM”);
system.exit(-1);
}

Question 2

error handling with exceptions
(you don’t have to throw an exception, you could just do if (exception occurred){
return whatever code you please;}

Answer 2

void method1(){
if(exception occurred)
throw new ExceptionType();
}

void method2(){
try{
method1();
} catch (ExceptionType e) {
}
}

Question 3

exceptions are objects derived from which class?

Answer 3

throwable
Throwable (); //no error message
Throwable(String msg); // with error message
String getMessage (); //return error message
void printStackTrace(); //record methods called, and location

Question 4

two types of errors

Answer 4

checked errors: must be handled by the programmer

unchecked errors: serious errors that a typical program should not be required to handle

Question 5

IO Exception(java.io)

Answer 5

used for generic I/O errors

Question 6

IllegalArgumentException(java.lang)

Answer 6

if method has passed in an illegal or inappropriate argument

Question 7

NullPointerException(java.lang)

Answer 7

a null reference is dereferenced

Question 8

ArrayIndexOutOfBoundsException(java.lang)

Answer 8

array subscript is invalid

Question 9

UnsupportedOperationException

Answer 9

a called operation does not exist