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/*
* Copyright (C) 2002-2020 Sebastiano Vigna
*
* 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 it.unimi.dsi.fastutil.objects;
import it.unimi.dsi.fastutil.Function;
/**
* A class providing static methods and objects that do useful things with
* type-specific functions.
*
* @see it.unimi.dsi.fastutil.Function
* @see java.util.Collections
*/
public final class Object2ObjectFunctions {
private Object2ObjectFunctions() {
}
/**
* An immutable class representing an empty type-specific function.
*
*
* This class may be useful to implement your own in case you subclass a
* type-specific function.
*/
public static class EmptyFunction extends AbstractObject2ObjectFunction
implements
java.io.Serializable,
Cloneable {
private static final long serialVersionUID = -7046029254386353129L;
protected EmptyFunction() {
}
@Override
public V get(final Object k) {
return (null);
}
@Override
public boolean containsKey(final Object k) {
return false;
}
@Override
public V defaultReturnValue() {
return (null);
}
@Override
public void defaultReturnValue(final V defRetValue) {
throw new UnsupportedOperationException();
}
@Override
public int size() {
return 0;
}
@Override
public void clear() {
}
@Override
public Object clone() {
return EMPTY_FUNCTION;
}
@Override
public int hashCode() {
return 0;
}
@Override
public boolean equals(final Object o) {
if (!(o instanceof Function))
return false;
return ((Function) o).size() == 0;
}
@Override
public String toString() {
return "{}";
}
private Object readResolve() {
return EMPTY_FUNCTION;
}
}
/**
* An empty type-specific function (immutable). It is serializable and
* cloneable.
*/
@SuppressWarnings("rawtypes")
public static final EmptyFunction EMPTY_FUNCTION = new EmptyFunction();
/**
* An immutable class representing a type-specific singleton function. Note that
* the default return value is still settable.
*
*
* Note that albeit the function is immutable, its default return value may be
* changed.
*
*
* This class may be useful to implement your own in case you subclass a
* type-specific function.
*/
public static class Singleton extends AbstractObject2ObjectFunction
implements
java.io.Serializable,
Cloneable {
private static final long serialVersionUID = -7046029254386353129L;
protected final K key;
protected final V value;
protected Singleton(final K key, final V value) {
this.key = key;
this.value = value;
}
@Override
public boolean containsKey(final Object k) {
return java.util.Objects.equals(key, k);
}
@Override
public V get(final Object k) {
return java.util.Objects.equals(key, k) ? value : defRetValue;
}
@Override
public int size() {
return 1;
}
@Override
public Object clone() {
return this;
}
}
/**
* Returns a type-specific immutable function containing only the specified
* pair. The returned function is serializable and cloneable.
*
*
* Note that albeit the returned function is immutable, its default return value
* may be changed.
*
* @param key
* the only key of the returned function.
* @param value
* the only value of the returned function.
* @return a type-specific immutable function containing just the pair
* {@code <key,value>}.
*/
public static Object2ObjectFunction singleton(final K key, V value) {
return new Singleton<>(key, value);
}
/** A synchronized wrapper class for functions. */
public static class SynchronizedFunction implements Object2ObjectFunction, java.io.Serializable {
private static final long serialVersionUID = -7046029254386353129L;
protected final Object2ObjectFunction function;
protected final Object sync;
protected SynchronizedFunction(final Object2ObjectFunction f, final Object sync) {
if (f == null)
throw new NullPointerException();
this.function = f;
this.sync = sync;
}
protected SynchronizedFunction(final Object2ObjectFunction f) {
if (f == null)
throw new NullPointerException();
this.function = f;
this.sync = this;
}
@Override
public V apply(final K key) {
synchronized (sync) {
return function.apply(key);
}
}
@Override
public int size() {
synchronized (sync) {
return function.size();
}
}
@Override
public V defaultReturnValue() {
synchronized (sync) {
return function.defaultReturnValue();
}
}
@Override
public void defaultReturnValue(final V defRetValue) {
synchronized (sync) {
function.defaultReturnValue(defRetValue);
}
}
@Override
public boolean containsKey(final Object k) {
synchronized (sync) {
return function.containsKey(k);
}
}
@Override
public V put(final K k, final V v) {
synchronized (sync) {
return function.put(k, v);
}
}
@Override
public V get(final Object k) {
synchronized (sync) {
return function.get(k);
}
}
@Override
public V remove(final Object k) {
synchronized (sync) {
return function.remove(k);
}
}
@Override
public void clear() {
synchronized (sync) {
function.clear();
}
}
@Override
public int hashCode() {
synchronized (sync) {
return function.hashCode();
}
}
@Override
public boolean equals(final Object o) {
if (o == this)
return true;
synchronized (sync) {
return function.equals(o);
}
}
@Override
public String toString() {
synchronized (sync) {
return function.toString();
}
}
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
synchronized (sync) {
s.defaultWriteObject();
}
}
}
/**
* Returns a synchronized type-specific function backed by the given
* type-specific function.
*
* @param f
* the function to be wrapped in a synchronized function.
* @return a synchronized view of the specified function.
* @see java.util.Collections#synchronizedMap(java.util.Map)
*/
public static Object2ObjectFunction synchronize(final Object2ObjectFunction f) {
return new SynchronizedFunction<>(f);
}
/**
* Returns a synchronized type-specific function backed by the given
* type-specific function, using an assigned object to synchronize.
*
* @param f
* the function to be wrapped in a synchronized function.
* @param sync
* an object that will be used to synchronize the access to the
* function.
* @return a synchronized view of the specified function.
* @see java.util.Collections#synchronizedMap(java.util.Map)
*/
public static Object2ObjectFunction synchronize(final Object2ObjectFunction f,
final Object sync) {
return new SynchronizedFunction<>(f, sync);
}
/** An unmodifiable wrapper class for functions. */
public static class UnmodifiableFunction extends AbstractObject2ObjectFunction
implements
java.io.Serializable {
private static final long serialVersionUID = -7046029254386353129L;
protected final Object2ObjectFunction function;
protected UnmodifiableFunction(final Object2ObjectFunction f) {
if (f == null)
throw new NullPointerException();
this.function = f;
}
@Override
public int size() {
return function.size();
}
@Override
public V defaultReturnValue() {
return function.defaultReturnValue();
}
@Override
public void defaultReturnValue(final V defRetValue) {
throw new UnsupportedOperationException();
}
@Override
public boolean containsKey(final Object k) {
return function.containsKey(k);
}
@Override
public V put(final K k, final V v) {
throw new UnsupportedOperationException();
}
@Override
public V get(final Object k) {
return function.get(k);
}
@Override
public V remove(final Object k) {
throw new UnsupportedOperationException();
}
@Override
public void clear() {
throw new UnsupportedOperationException();
}
@Override
public int hashCode() {
return function.hashCode();
}
@Override
public boolean equals(Object o) {
return o == this || function.equals(o);
}
@Override
public String toString() {
return function.toString();
}
}
/**
* Returns an unmodifiable type-specific function backed by the given
* type-specific function.
*
* @param f
* the function to be wrapped in an unmodifiable function.
* @return an unmodifiable view of the specified function.
* @see java.util.Collections#unmodifiableMap(java.util.Map)
*/
public static Object2ObjectFunction unmodifiable(final Object2ObjectFunction f) {
return new UnmodifiableFunction<>(f);
}
}