Improve null tests in 'concurrent.when'

Author: nicolaiparlog

src/main/java/org/codefx/libfx/concurrent/when/ExecuteAlwaysWhen.java

@@ -110,6 +110,10 @@ public class ExecuteAlwaysWhen<T> {
 	 *            the action which will be executed
 	 */
 	ExecuteAlwaysWhen(ObservableValue<T> observable, Predicate<? super T> condition, Consumer<? super T> action) {
+		assert observable != null : "The argument 'observable' must not be null.";
+		assert condition != null : "The argument 'condition' must not be null.";
+		assert action != null : "The argument 'action' must not be null.";
+
 		this.observable = observable;
 		this.condition = condition;
 		this.action = action;

src/main/java/org/codefx/libfx/concurrent/when/ExecuteOnceWhen.java

@@ -25,7 +25,7 @@
  * value (the one tested during {@code executeWhen()}) or one of several which were set by those threads.
  * <p>
  * Use {@link ExecuteWhen} to build an instance of this class.
- * 
+ *
  * @param <T>
  *            the type the observed {@link ObservableValue}'s wraps
  */
@@ -96,6 +96,10 @@ public class ExecuteOnceWhen<T> {
 	 *            the action which will be executed
 	 */
 	ExecuteOnceWhen(ObservableValue<T> observable, Predicate<? super T> condition, Consumer<? super T> action) {
+		assert observable != null : "The argument 'observable' must not be null.";
+		assert condition != null : "The argument 'condition' must not be null.";
+		assert action != null : "The argument 'action' must not be null.";
+
 		this.observable = observable;
 		this.condition = condition;
 		this.action = action;

src/main/java/org/codefx/libfx/concurrent/when/ExecuteWhen.java

@@ -49,6 +49,8 @@ public class ExecuteWhen<T> {
 	 *            the {@link ObservableValue} which will be observed by the created {@code Execute...When} instances
 	 */
 	private ExecuteWhen(ObservableValue<T> observable) {
+		Objects.requireNonNull(observable, "The argument 'observable' must not be null.");
+
 		this.observable = observable;
 		condition = Optional.empty();
 	}
@@ -79,6 +81,7 @@ public static <T> ExecuteWhen<T> on(ObservableValue<T> observable) {
 	 */
 	public ExecuteWhen<T> when(Predicate<? super T> condition) {
 		Objects.requireNonNull(condition, "The argument 'condition' must not be null.");
+
 		this.condition = Optional.of(condition);
 		return this;
 	}
@@ -104,6 +107,8 @@ public ExecuteWhen<T> when(Predicate<? super T> condition) {
 	 *             if {@link #when(Predicate)} was not called
 	 */
 	public ExecuteOnceWhen<T> thenOnce(Consumer<? super T> action) throws IllegalStateException {
+		Objects.requireNonNull(action, "The argument 'action' must not be null.");
+
 		ensureConditionWasSet();
 		return new ExecuteOnceWhen<T>(observable, condition.get(), action);
 	}
@@ -125,6 +130,8 @@ public ExecuteOnceWhen<T> thenOnce(Consumer<? super T> action) throws IllegalSta
 	 *             if {@link #when(Predicate)} was not called
 	 */
 	public ExecuteAlwaysWhen<T> thenAlways(Consumer<? super T> action) throws IllegalStateException {
+		Objects.requireNonNull(action, "The argument 'action' must not be null.");
+
 		ensureConditionWasSet();
 		return new ExecuteAlwaysWhen<T>(observable, condition.get(), action);
 	}
@@ -139,7 +146,7 @@ private void ensureConditionWasSet() throws IllegalStateException {
 		boolean noCondition = !condition.isPresent();
 		if (noCondition)
 			throw new IllegalStateException(
-					"Set a condition with 'when(Predicate<? super T>)' before calling any 'then' method.");
+					"Set a condition with 'when(Predicate<? super T>)' before calling any 'then...' method.");
 	}
 
 	// #end BUILD