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 * Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package com.sun.javafx.scene.control;

import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.beans.value.WeakChangeListener;

import java.util.HashMap;
import java.util.Map;
import java.util.function.Consumer;

public final class LambdaMultiplePropertyChangeListenerHandler {

    private final Map<ObservableValue<?>, Consumer<ObservableValue<?>>> propertyReferenceMap;
    private final ChangeListener<Object> propertyChangedListener;
    private final WeakChangeListener<Object> weakPropertyChangedListener;

    private static final Consumer<ObservableValue<?>> EMPTY_CONSUMER = e -> {};

    public LambdaMultiplePropertyChangeListenerHandler() {
        this.propertyReferenceMap = new HashMap<>();
        this.propertyChangedListener = (observable, oldValue, newValue) -> {
            // because all consumers are chained, this calls each consumer for the given property
            // in turn.
            propertyReferenceMap.getOrDefault(observable, EMPTY_CONSUMER).accept(observable);
        };
        this.weakPropertyChangedListener = new WeakChangeListener<>(propertyChangedListener);
    }

    
Subclasses can invoke this method to register that we want to listen to
property change events for the given property.
Params:
property – /**
     * Subclasses can invoke this method to register that we want to listen to
     * property change events for the given property.
     *
     * @param property
     */
    public final void registerChangeListener(ObservableValue<?> property, Consumer<ObservableValue<?>> consumer) {
        if (consumer == null) return;

        // we only add a listener if the propertyReferenceMap does not contain the property
        // (that is, we've added a consumer to this specific property for the first
        // time).
        if (!propertyReferenceMap.containsKey(property)) {
            property.addListener(weakPropertyChangedListener);
        }

        propertyReferenceMap.merge(property, consumer, Consumer::andThen);
    }

    // need to be careful here - removing all listeners on the specific property!
    public final Consumer<ObservableValue<?>> unregisterChangeListeners(ObservableValue<?> property) {
        property.removeListener(weakPropertyChangedListener);
        return propertyReferenceMap.remove(property);
    }

    public void dispose() {
        // unhook listeners
        for (ObservableValue<?> value : propertyReferenceMap.keySet()) {
            value.removeListener(weakPropertyChangedListener);
        }
        propertyReferenceMap.clear();
    }
}