1. Exception Handling in Java
Mr Hanley, Shenendehowa High School 9/22/2014
Filled out 10/17/2016

2. What is exception handling?
A: Java taking exception to the code you type in
A: All your code working except the important stuff
A: Handling mail messages that go awry
A: A robust mechanism for responding to run time errors

3. Throwing Exceptions
Java has defined a class Exception, which allows control of the program to go to catch blocks of code that are designed to act as safeguards
For example, when taking in a negative value a method can throw an exception to reject the negative value

4. Example public class Aircraft { private int altitude, fuel;
public void setAltitude(int alt) throws IllegalArgumentException {
if (alt < 0 ) throw new IllegalArgumentException(“Out of range”);
altitude = alt; //throw means quit the method look for a catch }

5. Flow
A try catch block should be used by the caller of methods that throw Exceptions so they program can jump back to the catch block when thrown
public class Client {
public static void main(String[] args){
Aircraft a1 = new Aircraft();
//To do: finish with a try catch and assignment
Scanner input = new Scanner(System.in);
int newAlt = input.nextInt();
try { a1.setAltitude(newAlt); } catch(IllegalArgumentException iae) { //This is the handling block System.out.println(“Naughy, naughty”); }

6. Finally Block
Use a finally block in order to clean up issues regardless of whether exceptions are thrown or not
try {
inVal = scan.nextDouble();
} catch (Exception e) {
System.out.println(" Bad Character");
errorSnd.play(); }
finally {
scan.nextLine(); //This fixes the problem of the Scanner looping with same value

7. Checked and Unchecked Exceptions
Checked exceptions: Checked exceptions are checked at compile-time. It means if a method is throwing a checked exception then it should handle the exception using try-catch block or it should declare the exception using throws keyword, otherwise the program will give a compilation error. It is named as checked exception because these exceptions are checked at Compile time. Opening a text file Unchecked exceptions: Unchecked exceptions are not checked at compile time. It means if your program is throwing an unchecked exception and even if you didn’t handle/declare that exception, the program won’t give a compilation error.  ArithmeticException Arithmetic error, such as divide-by-zero. ArrayIndexOutOfBoundsException Array index is out-of-bounds.

8. The End
throw new EndOfPowerPointException (“I’m out”);
The End