(NEW) Module "retry"

(NEW) Illustrative classes:
      - App: simulates a production application
      - BusinessOperation<T>: abstraction over any operation that can
        potentially fail
      - FindCustomer <: BusinessOperation<String>: illustrative
        operation that can throw an error
      - Retry <: BusinessOperation<T>: transparently implements the
        retry mechanism
      - Several "business" exceptions:
        - BusinessException: top-level
        - CustomerNotFoundException: can be ignored
        - DatabaseNotAvailableException: fatal error
(NEW) .puml and .png for UML

retry/etc/retry.urm.puml

@@ -0,0 +1,38 @@
+@startuml
+package com.iluwatar.retry {
+  class App {
+    - LOG : Logger {static}
+    - op : BusinessOperation<String> {static}
+    + App()
+    - errorNoRetry() {static}
+    - errorWithRetry() {static}
+    + main(args : String[]) {static}
+    - noErrors() {static}
+  }
+  interface BusinessOperation<T> {
+    + perform() : T {abstract}
+  }
+  class FindCustomer {
+    - customerId : String
+    - errors : Deque<BusinessException>
+    + FindCustomer(customerId : String, errors : BusinessException[])
+    + perform() : String
+  }
+  class Retry<T> {
+    - attempts : AtomicInteger
+    - delay : long
+    - errors : List<Exception>
+    - maxAttempts : int
+    - op : BusinessOperation<T>
+    - test : Predicate<Exception>
+    + Retry<T>(op : BusinessOperation<T>, maxAttempts : int, delay : long, ignoreTests : Predicate<Exception>[])
+    + attempts() : int
+    + errors() : List<Exception>
+    + perform() : T
+  }
+}
+Retry -->  "-op" BusinessOperation
+App -->  "-op" BusinessOperation
+FindCustomer ..|> BusinessOperation 
+Retry ..|> BusinessOperation 
+@enduml