http://fastutil.di.unimi.it/: fastutil extends the Java Collections Framework by providing type-specific maps, sets, lists and priority queues with a small memory footprint and fast access and insertion; provides also big (64-bit) arrays, sets and lists, and fast, practical I/O classes for binary and text files.
  • Sebastiano Vigna 
/*
	* Copyright (C) 2002-2019 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.doubles;
import it.unimi.dsi.fastutil.Function;

A class providing static methods and objects that do useful things with
type-specific functions.

See Also:
/**
 * 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 Double2IntFunctions {
	private Double2IntFunctions() {
	}
	
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.

/**
	 * An immutable class representing an empty type-specific function.
	 *
	 * <p>
	 * This class may be useful to implement your own in case you subclass a
	 * type-specific function.
	 */
	public static class EmptyFunction extends AbstractDouble2IntFunction implements java.io.Serializable, Cloneable {
		private static final long serialVersionUID = -7046029254386353129L;
		protected EmptyFunction() {
		}
		@Override
		public int get(final double k) {
			return (0);
		}
		@Override
		public boolean containsKey(final double k) {
			return false;
		}
		@Override
		public int defaultReturnValue() {
			return (0);
		}
		@Override
		public void defaultReturnValue(final int 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.

/**
	 * An empty type-specific function (immutable). It is serializable and
	 * cloneable.
	 */

	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.

/**
	 * An immutable class representing a type-specific singleton function. Note that
	 * the default return value is still settable.
	 *
	 * <p>
	 * Note that albeit the function is immutable, its default return value may be
	 * changed.
	 *
	 * <p>
	 * This class may be useful to implement your own in case you subclass a
	 * type-specific function.
	 */
	public static class Singleton extends AbstractDouble2IntFunction implements java.io.Serializable, Cloneable {
		private static final long serialVersionUID = -7046029254386353129L;
		protected final double key;
		protected final int value;
		protected Singleton(final double key, final int value) {
			this.key = key;
			this.value = value;
		}
		@Override
		public boolean containsKey(final double k) {
			return (Double.doubleToLongBits(key) == Double.doubleToLongBits(k));
		}
		@Override
		public int get(final double k) {
			return (Double.doubleToLongBits(key) == Double.doubleToLongBits(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.

Params:
  • key – 
           the only key of the returned function.
  • value – 
           the only value of the returned function.
Returns:a type-specific immutable function containing just the pair &lt;key,value&gt;.
/**
	 * Returns a type-specific immutable function containing only the specified
	 * pair. The returned function is serializable and cloneable.
	 *
	 * <p>
	 * 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 &lt;key,value&gt;}.
	 */
	public static Double2IntFunction singleton(final double key, int value) {
		return new Singleton(key, value);
	}
	
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.

Params:
  • key – 
           the only key of the returned function.
  • value – 
           the only value of the returned function.
Returns:a type-specific immutable function containing just the pair &lt;key,value&gt;.
/**
	 * Returns a type-specific immutable function containing only the specified
	 * pair. The returned function is serializable and cloneable.
	 *
	 * <p>
	 * 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 &lt;key,value&gt;}.
	 */
	public static Double2IntFunction singleton(final Double key, final Integer value) {
		return new Singleton((key).doubleValue(), (value).intValue());
	}
	
A synchronized wrapper class for functions. 
/** A synchronized wrapper class for functions. */
	public static class SynchronizedFunction implements Double2IntFunction, java.io.Serializable {
		private static final long serialVersionUID = -7046029254386353129L;
		protected final Double2IntFunction function;
		protected final Object sync;
		protected SynchronizedFunction(final Double2IntFunction f, final Object sync) {
			if (f == null)
				throw new NullPointerException();
			this.function = f;
			this.sync = sync;
		}
		protected SynchronizedFunction(final Double2IntFunction f) {
			if (f == null)
				throw new NullPointerException();
			this.function = f;
			this.sync = this;
		}
		@Override
		public int applyAsInt(double operand) {
			synchronized (sync) {
				return function.applyAsInt(operand);
			}
		}
		
{@inheritDoc}

Deprecated:Please use the corresponding type-specific method instead.
/**
		 * {@inheritDoc}
		 * 
		 * @deprecated Please use the corresponding type-specific method instead.
		 */
		@Deprecated
		@Override
		public Integer apply(final Double key) {
			synchronized (sync) {
				return function.apply(key);
			}
		}
		@Override
		public int size() {
			synchronized (sync) {
				return function.size();
			}
		}
		@Override
		public int defaultReturnValue() {
			synchronized (sync) {
				return function.defaultReturnValue();
			}
		}
		@Override
		public void defaultReturnValue(final int defRetValue) {
			synchronized (sync) {
				function.defaultReturnValue(defRetValue);
			}
		}
		@Override
		public boolean containsKey(final double k) {
			synchronized (sync) {
				return function.containsKey(k);
			}
		}
		@Deprecated
		@Override
		public boolean containsKey(final Object k) {
			synchronized (sync) {
				return function.containsKey(k);
			}
		}
		@Override
		public int put(final double k, final int v) {
			synchronized (sync) {
				return function.put(k, v);
			}
		}
		@Override
		public int get(final double k) {
			synchronized (sync) {
				return function.get(k);
			}
		}
		@Override
		public int remove(final double k) {
			synchronized (sync) {
				return function.remove(k);
			}
		}
		@Override
		public void clear() {
			synchronized (sync) {
				function.clear();
			}
		}
		
{@inheritDoc}

Deprecated:Please use the corresponding type-specific method instead.
/**
		 * {@inheritDoc}
		 * 
		 * @deprecated Please use the corresponding type-specific method instead.
		 */
		@Deprecated
		@Override
		public Integer put(final Double k, final Integer v) {
			synchronized (sync) {
				return function.put(k, v);
			}
		}
		
{@inheritDoc}

Deprecated:Please use the corresponding type-specific method instead.
/**
		 * {@inheritDoc}
		 * 
		 * @deprecated Please use the corresponding type-specific method instead.
		 */
		@Deprecated
		@Override
		public Integer get(final Object k) {
			synchronized (sync) {
				return function.get(k);
			}
		}
		
{@inheritDoc}

Deprecated:Please use the corresponding type-specific method instead.
/**
		 * {@inheritDoc}
		 * 
		 * @deprecated Please use the corresponding type-specific method instead.
		 */
		@Deprecated
		@Override
		public Integer remove(final Object k) {
			synchronized (sync) {
				return function.remove(k);
			}
		}
		@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.

Params:
  • f – 
           the function to be wrapped in a synchronized function.
See Also:
Returns:a synchronized view of the specified function.
/**
	 * 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 Double2IntFunction synchronize(final Double2IntFunction f) {
		return new SynchronizedFunction(f);
	}
	
Returns a synchronized type-specific function backed by the given
type-specific function, using an assigned object to synchronize.

Params:
  • f – 
           the function to be wrapped in a synchronized function.
  • sync – 
           an object that will be used to synchronize the access to the
           function.
See Also:
Returns:a synchronized view of the specified function.
/**
	 * 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 Double2IntFunction synchronize(final Double2IntFunction f, final Object sync) {
		return new SynchronizedFunction(f, sync);
	}
	
An unmodifiable wrapper class for functions. 
/** An unmodifiable wrapper class for functions. */
	public static class UnmodifiableFunction extends AbstractDouble2IntFunction implements java.io.Serializable {
		private static final long serialVersionUID = -7046029254386353129L;
		protected final Double2IntFunction function;
		protected UnmodifiableFunction(final Double2IntFunction f) {
			if (f == null)
				throw new NullPointerException();
			this.function = f;
		}
		@Override
		public int size() {
			return function.size();
		}
		@Override
		public int defaultReturnValue() {
			return function.defaultReturnValue();
		}
		@Override
		public void defaultReturnValue(final int defRetValue) {
			throw new UnsupportedOperationException();
		}
		@Override
		public boolean containsKey(final double k) {
			return function.containsKey(k);
		}
		@Override
		public int put(final double k, final int v) {
			throw new UnsupportedOperationException();
		}
		@Override
		public int get(final double k) {
			return function.get(k);
		}
		@Override
		public int remove(final double k) {
			throw new UnsupportedOperationException();
		}
		@Override
		public void clear() {
			throw new UnsupportedOperationException();
		}
		
{@inheritDoc}

Deprecated:Please use the corresponding type-specific method instead.
/**
		 * {@inheritDoc}
		 * 
		 * @deprecated Please use the corresponding type-specific method instead.
		 */
		@Deprecated
		@Override
		public Integer put(final Double k, final Integer v) {
			throw new UnsupportedOperationException();
		}
		
{@inheritDoc}

Deprecated:Please use the corresponding type-specific method instead.
/**
		 * {@inheritDoc}
		 * 
		 * @deprecated Please use the corresponding type-specific method instead.
		 */
		@Deprecated
		@Override
		public Integer get(final Object k) {
			return function.get(k);
		}
		
{@inheritDoc}

Deprecated:Please use the corresponding type-specific method instead.
/**
		 * {@inheritDoc}
		 * 
		 * @deprecated Please use the corresponding type-specific method instead.
		 */
		@Deprecated
		@Override
		public Integer remove(final Object k) {
			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.

Params:
  • f – 
           the function to be wrapped in an unmodifiable function.
See Also:
Returns:an unmodifiable view of the specified function.
/**
	 * 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 Double2IntFunction unmodifiable(final Double2IntFunction f) {
		return new UnmodifiableFunction(f);
	}
	
An adapter for mapping generic total functions to partial primitive
functions.

/**
	 * An adapter for mapping generic total functions to partial primitive
	 * functions.
	 */
	public static class PrimitiveFunction implements Double2IntFunction {
		protected final java.util.function.Function<? super Double, ? extends Integer> function;
		protected PrimitiveFunction(java.util.function.Function<? super Double, ? extends Integer> function) {
			this.function = function;
		}
		@Override
		public boolean containsKey(double key) {
			return function.apply(Double.valueOf(key)) != null;
		}

		@Deprecated
		@Override
		public boolean containsKey(Object key) {
			if (key == null)
				return false;
			return function.apply((Double) (key)) != null;
		}

		@Override
		public int get(double key) {
			Integer v = function.apply(Double.valueOf(key));
			if (v == null)
				return defaultReturnValue();
			return (v).intValue();
		}

		@Deprecated
		@Override
		public Integer get(Object key) {
			if (key == null)
				return null;
			return function.apply((Double) key);
		}
		@Deprecated
		@Override
		public Integer put(final Double key, final Integer value) {
			throw new UnsupportedOperationException();
		}
	}
	
Returns a (partial) type-specific function based on the given total generic
function.

 The returned function contains all keys which are not mapped to null. If the function already is a primitive function, it is returned without changes. 

Warning: If the given function is a “widened” primitive function (e.g. an Int2IntFunction given to Short2ShortFunctions), it still is wrapped into a proxy, decreasing performance. 
Params:
  • f – 
           the function to be converted to a type-specific function.
Throws:
See Also:
Returns:a primitive view of the specified function.
Since:8.1.0
/**
	 * Returns a (partial) type-specific function based on the given total generic
	 * function.
	 * <p>
	 * The returned function contains all keys which are not mapped to {@code null}.
	 * If the function already is a primitive function, it is returned without
	 * changes.
	 * <p>
	 * <strong>Warning</strong>: If the given function is a &ldquo;widened&rdquo;
	 * primitive function (e.g. an {@code Int2IntFunction} given to
	 * {@code Short2ShortFunctions}), it still is wrapped into a proxy, decreasing
	 * performance.
	 *
	 * @param f
	 *            the function to be converted to a type-specific function.
	 * @return a primitive view of the specified function.
	 * @throws NullPointerException
	 *             if {@code f} is null.
	 * @see PrimitiveFunction
	 * @since 8.1.0
	 */

	public static Double2IntFunction primitive(final java.util.function.Function<? super Double, ? extends Integer> f) {
		java.util.Objects.requireNonNull(f);
		if (f instanceof Double2IntFunction)
			return (Double2IntFunction) f;
		if (f instanceof java.util.function.DoubleToIntFunction)
			return ((java.util.function.DoubleToIntFunction) f)::applyAsInt;
		return new PrimitiveFunction(f);
	}
}