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package javafx.beans.binding;

import javafx.beans.value.ObservableValue;
import javafx.collections.ObservableList;
import com.sun.javafx.collections.annotations.ReturnsUnmodifiableCollection;

/**
 * A {@code Binding} calculates a value that depends on one or more sources. The
 * sources are usually called the dependency of a binding. A binding observes
 * its dependencies for changes and updates its value automatically.
 * 

* While a dependency of a binding can be anything, it is almost always an * implementation of {@link javafx.beans.value.ObservableValue}. {@code Binding} * implements {@code ObservableValue} allowing to use it in another binding. * With that one can assemble very complex bindings from simple bindings. *

* All bindings in the JavaFX 2.0 runtime are calculated lazily. That means, if * a dependency changes, the result of a binding is not immediately * recalculated, but it is marked as invalid. Next time the value of an invalid * binding is requested, it is recalculated. *

* It is recommended to use one of the base classes defined in this package * (e.g. {@link DoubleBinding}) to define a custom binding, because these * classes already provide most of the needed functionality. See * {@link DoubleBinding} for an example. * * @see DoubleBinding * * * @since JavaFX 2.0 */ public interface Binding extends ObservableValue { /** * Checks if a binding is valid. * * @return {@code true} if the {@code Binding} is valid, {@code false} * otherwise */ boolean isValid(); /** * Mark a binding as invalid. This forces the recalculation of the value of * the {@code Binding} next time it is request. */ void invalidate(); /** * Returns the dependencies of a binding in an unmodifiable * {@link javafx.collections.ObservableList}. The implementation is * optional. The main purpose of this method is to support developers during * development. It allows to explore and monitor dependencies of a binding * during runtime. *

* Because this method should not be used in production code, it is * recommended to implement this functionality as sparse as possible. For * example if the dependencies do not change, each call can generate a new * {@code ObservableList}, avoiding the necessity to store the result. * * @return an unmodifiable {@code} ObservableList of the dependencies */ @ReturnsUnmodifiableCollection ObservableList getDependencies(); /** * Signals to the {@code Binding} that it will not be used anymore and any * references can be removed. A call of this method usually results in the * binding stopping to observe its dependencies by unregistering its * listener(s). The implementation is optional. *

* All bindings in our implementation use instances of * {@link javafx.beans.WeakInvalidationListener}, which means usually * a binding does not need to be disposed. But if you plan to use your * application in environments that do not support {@code WeakReferences} * you have to dispose unused {@code Bindings} to avoid memory leaks. */ void dispose(); }





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