Merge pull request #121 from shannah/add_Observer_and_Observable

Add observer and observable

teavm-classlib/src/main/java/org/teavm/classlib/java/util/TObservable.java

@@ -0,0 +1,141 @@
+/*
+ * Copyright 2015 Steve Hannah.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.teavm.classlib.java.util;
+
+/**
+ *
+ * @author shannah
+ */
+public class TObservable {
+    TList<TObserver> observers = new TArrayList<TObserver>();
+
+    boolean changed = false;
+
+    /**
+     * Constructs a new {@code Observable} object.
+     */
+    public TObservable() {
+        super();
+    }
+
+    /**
+     * Adds the specified observer to the list of observers. If it is already
+     * registered, it is not added a second time.
+     * 
+     * @param observer
+     *            the Observer to add.
+     */
+    public void addObserver(TObserver observer) {
+        if (observer == null) {
+            throw new NullPointerException();
+        }
+        synchronized (this) {
+            if (!observers.contains(observer))
+                observers.add(observer);
+        }
+    }
+
+    /**
+     * Clears the changed flag for this {@code Observable}. After calling
+     * {@code clearChanged()}, {@code hasChanged()} will return {@code false}.
+     */
+    protected void clearChanged() {
+        changed = false;
+    }
+
+    /**
+     * Returns the number of observers registered to this {@code Observable}.
+     * 
+     * @return the number of observers.
+     */
+    public int countObservers() {
+        return observers.size();
+    }
+
+    /**
+     * Removes the specified observer from the list of observers. Passing null
+     * won't do anything.
+     * 
+     * @param observer
+     *            the observer to remove.
+     */
+    public synchronized void deleteObserver(TObserver observer) {
+        observers.remove(observer);
+    }
+
+    /**
+     * Removes all observers from the list of observers.
+     */
+    public synchronized void deleteObservers() {
+        observers.clear();
+    }
+
+    /**
+     * Returns the changed flag for this {@code Observable}.
+     * 
+     * @return {@code true} when the changed flag for this {@code Observable} is
+     *         set, {@code false} otherwise.
+     */
+    public boolean hasChanged() {
+        return changed;
+    }
+
+    /**
+     * If {@code hasChanged()} returns {@code true}, calls the {@code update()}
+     * method for every observer in the list of observers using null as the
+     * argument. Afterwards, calls {@code clearChanged()}.
+     * <p>
+     * Equivalent to calling {@code notifyObservers(null)}.
+     */
+    public void notifyObservers() {
+        notifyObservers(null);
+    }
+
+    /**
+     * If {@code hasChanged()} returns {@code true}, calls the {@code update()}
+     * method for every Observer in the list of observers using the specified
+     * argument. Afterwards calls {@code clearChanged()}.
+     * 
+     * @param data
+     *            the argument passed to {@code update()}.
+     */
+    @SuppressWarnings("unchecked")
+    public void notifyObservers(Object data) {
+        int size = 0;
+        TObserver[] arrays = null;
+        synchronized (this) {
+            if (hasChanged()) {
+                clearChanged();
+                size = observers.size();
+                arrays = new TObserver[size];
+                observers.toArray(arrays);
+            }
+        }
+        if (arrays != null) {
+            for (TObserver observer : arrays) {
+                observer.update(this, data);
+            }
+        }
+    }
+
+    /**
+     * Sets the changed flag for this {@code Observable}. After calling
+     * {@code setChanged()}, {@code hasChanged()} will return {@code true}.
+     */
+    protected void setChanged() {
+        changed = true;
+    }
+}

teavm-classlib/src/main/java/org/teavm/classlib/java/util/TObserver.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2015 Steve Hannah.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.teavm.classlib.java.util;
+
+
+/**
+ *
+ * @author shannah
+ */
+public interface TObserver {
+    /**
+     * This method is called if the specified {@code Observable} object's
+     * {@code notifyObservers} method is called (because the {@code Observable} 
+     * object has been updated.
+     * 
+     * @param observable
+     *            the {@link Observable} object.
+     * @param data
+     *            the data passed to {@link Observable#notifyObservers(Object)}.
+     */
+    void update(TObservable observable, Object data);
+}