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/*
* Copyright (c) 2023 Qualcomm Innovation Center, Inc.
* and other copyright owners as documented in the project's IP log.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.internal.util;
import java.lang.ref.SoftReference;
import java.util.Optional;
/**
* Interface representing a reference to a potentially mutable optional object.
*
* @param <T>
* type of the mutable optional object
*
* @since 6.7
*/
public interface Optionally<T> {
/**
* A permanently empty Optionally
*
* @param <T>
* type of the mutable optional object
*
*/
public class Empty<T> implements Optionally<T> {
@Override
public void clear() {
// empty
}
@Override
public Optional<T> getOptional() {
return Optional.empty();
}
}
/**
* A permanent(hard) reference to an object
*
* @param <T>
* type of the mutable optional object
*
*/
public class Hard<T> implements Optionally<T> {
/**
* The mutable optional object
*/
protected T element;
/**
* @param element
* the mutable optional object
*/
public Hard(T element) {
this.element = element;
}
@Override
public void clear() {
element = null;
}
@Override
public Optional<T> getOptional() {
return Optional.ofNullable(element);
}
}
/**
* A SoftReference Optionally
*
* @param <T>
* type of the mutable optional object
*
*/
public class Soft<T> extends SoftReference<T> implements Optionally<T> {
/**
* @param t
* the mutable optional object
*/
public Soft(T t) {
super(t);
}
@Override
public Optional<T> getOptional() {
return Optional.ofNullable(get());
}
}
/**
* The empty Optionally
*/
public static final Optionally<?> EMPTY = new Empty<>();
/**
* @param <T>
* type of the empty Optionally
* @return the empty Optionally
*/
@SuppressWarnings("unchecked")
public static <T> Optionally<T> empty() {
return (Optionally<T>) EMPTY;
}
/**
* Clear the object
*
*/
void clear();
/**
* Get an Optional representing the current state of the object
*
* @return the mutable optional object
*/
Optional<T> getOptional();
}
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