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/*
* Copyright (C) 2002-2022 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 V getOrDefault(final Object k, final V defaultValue) { return defaultValue; }
@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 V getOrDefault(final Object k, final V defaultValue) { return java.util.Objects.equals(key, k) ? value : defaultValue; }
@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 getOrDefault(final Object k, final V defaultValue) { synchronized(sync) { return function.getOrDefault(k, defaultValue); } }
@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
@SuppressWarnings("unchecked")
public V getOrDefault(final Object k, final V defaultValue) { return ((Object2ObjectFunction ) function).getOrDefault(k, defaultValue); }
@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); }
}