aQute.bnd.memoize.CloseableMemoize Maven / Gradle / Ivy
package aQute.bnd.memoize;
import java.util.function.Consumer;
import java.util.function.Supplier;
/**
* Closeable memoizing supplier.
*
* This type extends {@link Memoize} and {@code AutoCloseable}.
*
* @param Type of the value returned.
*/
public interface CloseableMemoize extends Memoize, AutoCloseable {
/**
* Creates an AutoCloseable supplier which memoizes the AutoCloseable value
* returned by the specified supplier.
*
* When the returned supplier is called to get a value, it will call the
* specified supplier at most once to obtain a value.
*
* When {@code close()} is called on the returned supplier, it will call
* {@code close()} on the memoized value, if present, and dereference the
* value. After {@code close()} is called on the returned supplier, the
* {@link #get()} and {@link #accept(Consumer)} methods of the returned
* supplier will throw an {@code IllegalStateException}.
*
* @param Type of the value returned by the supplier.
* @param supplier The source supplier. Must not be {@code null}. The
* supplier should not return a {@code null} value. If the
* supplier does return a {@code null} value, the returned
* supplier will be marked closed and its {@link #get()} and
* {@link #accept(Consumer)} methods will throw an
* {@code IllegalStateException}.
* @return A memoized supplier wrapping the specified supplier.
*/
static CloseableMemoize closeableSupplier(Supplier supplier) {
if (supplier instanceof CloseableMemoizingSupplier) {
@SuppressWarnings("unchecked")
CloseableMemoize memoized = (CloseableMemoize) supplier;
return memoized;
}
return new CloseableMemoizingSupplier<>(supplier);
}
/**
* Returns whether this memoizing supplier is closed.
*
* @return {@code true} If this memoizing supplier is closed; otherwise
* {@code false}.
*/
boolean isClosed();
/**
* Get the memoized AutoCloseable value.
*
* @return The memoized AutoCloseable value.
* @throws IllegalStateException If this memoizing supplier
* {@link #isClosed() is closed}.
*/
@Override
S get();
/**
* Call the consumer with the value of this memoizing supplier.
*
* This method will block closing this memoizing supplier while the consumer
* is executing.
*
* @param consumer The consumer to accept the value of this memoizing
* supplier. Must not be {@code null}.
* @return This memoizing supplier.
* @throws IllegalStateException If this memoizing supplier
* {@link #isClosed() is closed}.
*/
@Override
CloseableMemoize accept(Consumer consumer);
/**
* If a value is memoized, call the consumer with the value of this
* memoizing supplier. Otherwise do nothing.
*
* This method will block closing this memoizing supplier while the consumer
* is executing.
*
* @param consumer The consumer to accept the value of this memoizing
* supplier if a value is memoized. Must not be {@code null} if a
* value is memoized.
* @return This memoizing supplier.
*/
@Override
CloseableMemoize ifPresent(Consumer consumer);
}