// concurrent/CatchCompletableExceptions.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
import java.util.concurrent.*;

public class CatchCompletableExceptions {
 static void handleException(int failcount) {
 // Call the Function only if there's an
 // exception, must produce same type as came in:
 CompletableExceptions
 .test("exceptionally", failcount)
 .exceptionally((ex) -> { // Function
 if(ex == null)
 System.out.println("I don't get it yet");
 return new Breakable(ex.getMessage(), 0);
 })
 .thenAccept(str ->
 System.out.println("result: " + str));

 // Create a new result (recover):
 CompletableExceptions
 .test("handle", failcount)
 .handle((result, fail) -> { // BiFunction
 if(fail != null)
 return "Failure recovery object";
 else
 return result + " is good";
 })
 .thenAccept(str ->
 System.out.println("result: " + str));

 // Do something but pass the same result through:
 CompletableExceptions
 .test("whenComplete", failcount)
 .whenComplete((result, fail) -> { // BiConsumer
 if(fail != null)
 System.out.println("It failed");
 else
 System.out.println(result + " OK");
 })
 .thenAccept(r ->
 System.out.println("result: " + r));
 }
 public static void main(String[] args) {
 System.out.println("**** Failure Mode ****");
 handleException(2);
 System.out.println("**** Success Mode ****");
 handleException(0);
 }
}
/* Output:
**** Failure Mode ****
Breakable_exceptionally [1]
Throwing Exception for exceptionally
result: Breakable_java.lang.RuntimeException:
Breakable_exceptionally failed [0]
Breakable_handle [1]
Throwing Exception for handle
result: Failure recovery object
Breakable_whenComplete [1]
Throwing Exception for whenComplete
It failed
**** Success Mode ****
Breakable_exceptionally [-1]
Breakable_exceptionally [-2]
Breakable_exceptionally [-3]
Breakable_exceptionally [-4]
result: Breakable_exceptionally [-4]
Breakable_handle [-1]
Breakable_handle [-2]
Breakable_handle [-3]
Breakable_handle [-4]
result: Breakable_handle [-4] is good
Breakable_whenComplete [-1]
Breakable_whenComplete [-2]
Breakable_whenComplete [-3]
Breakable_whenComplete [-4]
Breakable_whenComplete [-4] OK
result: Breakable_whenComplete [-4]
*/