diff --git a/promise/etc/promise.png b/promise/etc/promise.png
new file mode 100644
index 000000000..1a0f67108
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diff --git a/promise/etc/promise.ucls b/promise/etc/promise.ucls
new file mode 100644
index 000000000..fe3c6c2e0
--- /dev/null
+++ b/promise/etc/promise.ucls
@@ -0,0 +1,115 @@
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diff --git a/promise/src/main/java/com/iluwatar/promise/App.java b/promise/src/main/java/com/iluwatar/promise/App.java
index 3390f2a23..6ce7de994 100644
--- a/promise/src/main/java/com/iluwatar/promise/App.java
+++ b/promise/src/main/java/com/iluwatar/promise/App.java
@@ -1,5 +1,28 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
package com.iluwatar.promise;
+import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
@@ -7,14 +30,31 @@ import java.util.concurrent.Executors;
/**
*
- * Application that uses promise pattern.
+ * The Promise object is used for asynchronous computations. A Promise represents an operation that
+ * hasn't completed yet, but is expected in the future.
+ *
+ *
A Promise represents a proxy for a value not necessarily known when the promise is created. It
+ * allows you to associate dependent promises to an asynchronous action's eventual success value or
+ * failure reason. This lets asynchronous methods return values like synchronous methods: instead of the final
+ * value, the asynchronous method returns a promise of having a value at some point in the future.
+ *
+ *
Promises provide a few advantages over callback objects:
+ *
+ * - Functional composition and error handling
+ *
- Prevents callback hell and provides callback aggregation
+ *
+ *
+ * @see CompletableFuture
*/
public class App {
+ private App() {
+ }
+
/**
* Program entry point
* @param args arguments
- * @throws InterruptedException if main thread is interruped.
+ * @throws InterruptedException if main thread is interrupted.
* @throws ExecutionException if an execution error occurs.
*/
public static void main(String[] args) throws InterruptedException, ExecutionException {
diff --git a/promise/src/main/java/com/iluwatar/promise/Promise.java b/promise/src/main/java/com/iluwatar/promise/Promise.java
index 03977c541..fe7dc6f9f 100644
--- a/promise/src/main/java/com/iluwatar/promise/Promise.java
+++ b/promise/src/main/java/com/iluwatar/promise/Promise.java
@@ -1,3 +1,25 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
package com.iluwatar.promise;
import java.util.concurrent.Callable;
@@ -8,6 +30,7 @@ import java.util.function.Function;
/**
* Implements the promise pattern.
+ *
* @param type of result.
*/
public class Promise extends PromiseSupport {
@@ -41,7 +64,7 @@ public class Promise extends PromiseSupport {
postFulfillment();
}
- void postFulfillment() {
+ private void postFulfillment() {
if (fulfillmentAction == null) {
return;
}
diff --git a/promise/src/main/java/com/iluwatar/promise/PromiseSupport.java b/promise/src/main/java/com/iluwatar/promise/PromiseSupport.java
new file mode 100644
index 000000000..dde2ca452
--- /dev/null
+++ b/promise/src/main/java/com/iluwatar/promise/PromiseSupport.java
@@ -0,0 +1,119 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.promise;
+
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+/**
+ * A really simplified implementation of future that allows completing it successfully with a value
+ * or exceptionally with an exception.
+ */
+class PromiseSupport implements Future {
+
+ static final int RUNNING = 1;
+ static final int FAILED = 2;
+ static final int COMPLETED = 3;
+
+ final Object lock;
+
+ volatile int state = RUNNING;
+ T value;
+ Exception exception;
+
+ PromiseSupport() {
+ this.lock = new Object();
+ }
+
+ void fulfill(T value) {
+ this.value = value;
+ this.state = COMPLETED;
+ synchronized (lock) {
+ lock.notifyAll();
+ }
+ }
+
+ void fulfillExceptionally(Exception exception) {
+ this.exception = exception;
+ this.state = FAILED;
+ synchronized (lock) {
+ lock.notifyAll();
+ }
+ }
+
+ @Override
+ public boolean cancel(boolean mayInterruptIfRunning) {
+ return false;
+ }
+
+ @Override
+ public boolean isCancelled() {
+ return false;
+ }
+
+ @Override
+ public boolean isDone() {
+ return state > RUNNING;
+ }
+
+ @Override
+ public T get() throws InterruptedException, ExecutionException {
+ if (state == COMPLETED) {
+ return value;
+ } else if (state == FAILED) {
+ throw new ExecutionException(exception);
+ } else {
+ synchronized (lock) {
+ lock.wait();
+ if (state == COMPLETED) {
+ return value;
+ } else {
+ throw new ExecutionException(exception);
+ }
+ }
+ }
+ }
+
+ @Override
+ public T get(long timeout, TimeUnit unit)
+ throws InterruptedException, ExecutionException, TimeoutException {
+ if (state == COMPLETED) {
+ return value;
+ } else if (state == FAILED) {
+ throw new ExecutionException(exception);
+ } else {
+ synchronized (lock) {
+ lock.wait(unit.toMillis(timeout));
+ if (state == COMPLETED) {
+ return value;
+ } else if (state == FAILED) {
+ throw new ExecutionException(exception);
+ } else {
+ throw new TimeoutException();
+ }
+ }
+ }
+ }
+}
\ No newline at end of file
diff --git a/promise/src/test/java/com/iluwatar/promise/AppTest.java b/promise/src/test/java/com/iluwatar/promise/AppTest.java
index b2628127c..1d1cb061d 100644
--- a/promise/src/test/java/com/iluwatar/promise/AppTest.java
+++ b/promise/src/test/java/com/iluwatar/promise/AppTest.java
@@ -1,3 +1,25 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
package com.iluwatar.promise;
import java.util.concurrent.ExecutionException;
diff --git a/promise/src/test/java/com/iluwatar/promise/PromiseTest.java b/promise/src/test/java/com/iluwatar/promise/PromiseTest.java
index 842558589..de0ecb6d7 100644
--- a/promise/src/test/java/com/iluwatar/promise/PromiseTest.java
+++ b/promise/src/test/java/com/iluwatar/promise/PromiseTest.java
@@ -1,3 +1,25 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
package com.iluwatar.promise;
import static org.junit.Assert.assertEquals;