raise() method to expose(throw) exceptions

README.md

@@ -49,6 +49,7 @@ The Try api is meant to be similar to the Optional type so has the same function
 - filter((x) -> isTrue(x)) - If Success, returns the same Success if the predicate succeeds, otherwise, returns a Failure with type NoSuchElementException.
 - onSuccess((x) -> f(x)) execute some code on success - takes Consumer (eg requires no return value).
 - onFailure((x) -> f(x)) execute some code on failure - takes Consumer (eg requires no return value).
+- raise(x) -> will throw an exception of type x when it happens
 - orElse(x) will return the success value of the Try in success case or the value x in failure case.
 - orElseTry(f) will return the success value of the Try in success case or a new Try(f) in the failure case.
 - orElseThrow(() -> throw new T) gets result or on failure will throw checked exception of type T

build.sbt

@@ -4,7 +4,7 @@ organization := "com.jason-goodwin"
 
 libraryDependencies ++= Seq(
   "com.novocode" % "junit-interface" % "0.11" % "test",
-  "junit" % "junit" % "4.11" % "test"
+  "junit" % "junit" % "4.12" % "test"
 )
 
 crossPaths := false

src/main/java/com/jasongoodwin/monads/Try.java

@@ -142,6 +142,14 @@ public static <U> Try<U> ofFailable(TrySupplier<U> f) {
      */
     public abstract <E extends Throwable> Try<T> onFailure(TryConsumer<Throwable, E> action) throws E;
 
+    /**
+     * When the clazz failure type happens, that exception is thrown
+     * @param clazz the expected exception class
+     * @return new composed Try
+     * @throws E if the failure type is the on provided
+     */
+    public abstract <E extends Throwable> Try<T> raise(Class<E> clazz) throws E;
+
     /**
      * If a Try is a Success and the predicate holds true, the Success is passed further.
      * Otherwise (Failure or predicate doesn't hold), pass Failure.
@@ -276,6 +284,11 @@ public Optional<T> toOptional() {
     public <E extends Throwable> Try<T> onFailure(TryConsumer<Throwable, E> action) {
       return this;
     }
+
+    @Override
+    public <E extends Throwable> Try<T> raise(Class<E> clazz) throws E {
+      return this;
+    }
 }
 
 
@@ -365,4 +378,14 @@ public <E extends Throwable> Try<T> onFailure(TryConsumer<Throwable, E> action)
       action.accept(e);
       return this;
     }
+
+    @Override
+    public <E extends Throwable> Try<T> raise(Class<E> clazz) throws E {
+        return onFailure( t -> {
+            if (clazz.isAssignableFrom(t.getClass())) {
+                throw (E) t;
+            }
+        } );
+    }
+
 }

src/test/java/com/jasongoodwin/monads/RaiseException.java

@@ -0,0 +1,7 @@
+package com.jasongoodwin.monads;
+
+public class RaiseException extends Exception {
+    public RaiseException(String message) {
+        super(message);
+    }
+}