functions.java
/*
* Java Genetic Algorithm Library (@__identifier__@).
* Copyright (c) @__year__@ Franz Wilhelmstötter
*
* 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.
*
* Author:
* Franz Wilhelmstötter (franz.wilhelmstoetter@gmx.at)
*/
package org.jenetics.util;
import static java.lang.String.format;
import static java.util.Objects.requireNonNull;
import java.io.Serializable;
import java.util.Objects;
import org.jscience.mathematics.number.Float64;
import org.jscience.mathematics.number.Integer64;
/**
* This class contains some short general purpose functions.
*
* @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
* @since 1.0
* @version 1.0 — <em>$Date: 2014-02-27 $</em>
*/
public final class functions extends StaticObject {
private functions() {}
/**
* Convert an object to a string by calling the objects {@link Object#toString()}
* method.
*/
public static final Function<Object, String>
ObjectToString = new Function<Object, String>() {
@Override public String apply(final Object value) {
return Objects.toString(value);
}
};
/**
* Convert a string value to its length.
*/
public static final Function<String, Integer>
StringLength = new Function<String, Integer>() {
@Override public Integer apply(final String value) {
return value.length();
}
};
/**
* Convert a string to an integer. If the string can't be converted, an
* {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
* method.
*/
public static final Function<String, Integer>
StringToInteger = new Function<String, Integer>() {
@Override public Integer apply(final String value) {
return Integer.parseInt(value);
}
};
/**
* Convert a string to a long. If the string can't be converted, an
* {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
* method.
*/
public static final Function<String, Long>
StringToLong = new Function<String, Long>() {
@Override public Long apply(final String value) {
return Long.parseLong(value);
}
};
/**
* Convert a string to an Integer64. If the string can't be converted, an
* {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
* method.
*
* @deprecated Will be removed.
*/
@Deprecated
public static final Function<String, Integer64>
StringToInteger64 = new Function<String, Integer64>() {
@Override public Integer64 apply(final String value) {
return Integer64.valueOf(value);
}
};
/**
* Convert a string to a float. If the string can't be converted, an
* {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
* method.
*/
public static final Function<String, Float>
StringToFloat = new Function<String, Float>() {
@Override public Float apply(final String value) {
return Float.parseFloat(value);
}
};
/**
* Convert a string to a double. If the string can't be converted, an
* {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
* method.
*/
public static final Function<String, Double>
StringToDouble = new Function<String, Double>() {
@Override public Double apply(final String value) {
return Double.parseDouble(value);
}
};
/**
* Convert a string to a Float64. If the string can't be converted, an
* {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
* method.
*
* @deprecated Will be removed.
*/
@Deprecated
public static final Function<String, Float64>
StringToFloat64 = new Function<String, Float64>() {
@Override public Float64 apply(final String value) {
return Float64.valueOf(value);
}
};
/**
* Convert a {@link Float64} value to a {@link Double} value.
*
* @deprecated Will be removed.
*/
@Deprecated
public static final Function<Float64, Double>
Float64ToDouble = new Function<Float64, Double>() {
@Override public Double apply(final Float64 value) {
return value.doubleValue();
}
};
/**
* Convert a {@link Double} value to a {@link Float64} value.
*
* @deprecated Will be removed.
*/
@Deprecated
public static final Function<Double, Float64>
DoubleToFloat64 = new Function<Double, Float64>() {
@Override public Float64 apply(final Double value) {
return Float64.valueOf(value);
}
};
/**
* Convert a {@link Integer64} value to a {@link Long} value.
*
* @deprecated Will be removed.
*/
@Deprecated
public static final Function<Integer64, Long>
Integer64ToLong = new Function<Integer64, Long>() {
@Override public Long apply(final Integer64 value) {
return value.longValue();
}
};
/**
* Convert a {link Long} value to a {@link Integer64} value.
*
* @deprecated Will be removed.
*/
@Deprecated
public static final Function<Long, Integer64>
LongToInteger64 = new Function<Long, Integer64>() {
@Override public Integer64 apply(final Long value) {
return Integer64.valueOf(value);
}
};
/**
* A predicate which return {@code true} if an given value is {@code null}.
*/
public static final Function<Object, Boolean>
Null = new Function<Object, Boolean>() {
@Override public Boolean apply(final Object object) {
return object == null ? Boolean.TRUE : Boolean.FALSE;
}
@Override public String toString() {
return format("%s", getClass().getSimpleName());
}
};
/**
* Return a predicate which negates the return value of the given predicate.
*
* @param <T> the value type to check.
* @param a the predicate to negate.
* @return a predicate which negates the return value of the given predicate.
* @throws NullPointerException if the given predicate is {@code null}.
*/
public static <T> Function<T, Boolean> not(final Function<? super T, Boolean> a) {
requireNonNull(a);
return new Function<T, Boolean>() {
@Override public Boolean apply(final T object) {
return a.apply(object) ? Boolean.FALSE : Boolean.TRUE;
}
@Override public String toString() {
return format("%s[%s]", getClass().getSimpleName(), a);
}
};
}
/**
* Return a {@code and} combination of the given predicates.
*
* @param <T> the value type to check.
* @param a the first predicate
* @param b the second predicate
* @return a {@code and} combination of the given predicates.
* @throws NullPointerException if one of the given predicates is
* {@code null}.
*/
public static <T> Function<T, Boolean> and(
final Function<? super T, Boolean> a,
final Function<? super T, Boolean> b
) {
requireNonNull(a);
requireNonNull(b);
return new Function<T, Boolean>() {
@Override public Boolean apply(final T object) {
return a.apply(object) && b.apply(object);
}
@Override public String toString() {
return format("%s[%s, %s]", getClass().getSimpleName(), a, b);
}
};
}
/**
* Return a {@code or} combination of the given predicates.
*
* @param <T> the value type to check.
* @param a the first predicate
* @param b the second predicate
* @return a {@code and} combination of the given predicates.
* @throws NullPointerException if one of the given predicates is
* {@code null}.
*/
public static <T> Function<T, Boolean> or(
final Function<? super T, Boolean> a,
final Function<? super T, Boolean> b
) {
requireNonNull(a);
requireNonNull(b);
return new Function<T, Boolean>() {
@Override public Boolean apply(final T object) {
return a.apply(object) || b.apply(object);
}
@Override public String toString() {
return format(
"%s[%s, %s]",
getClass().getSimpleName(), a, b
);
}
};
}
private static final class Identity
implements Function<Object, Object>, Serializable
{
private static final long serialVersionUID = 1L;
@Override
public Object apply(final Object value) {
return value;
}
}
private static Function<Object, Object> IDENTITY = new Identity();
/**
* Return the identity function for the given type.
*
* @return the identity function for the given type.
*/
@SuppressWarnings("unchecked")
public static <T> Function<T, T> Identity() {
return (Function<T, T>)IDENTITY;
}
public static <A, B, C> Function<A, C> compose(
final Function<A, B> f1,
final Function<B, C> f2
) {
requireNonNull(f1, "Function 1");
requireNonNull(f2, "Function 2");
return new Function<A, C>() {
@Override public C apply(A value) {
return f2.apply(f1.apply(value));
}
};
}
public static <A, B, C, D> Function<A, D> compose(
final Function<A, B> f1,
final Function<B, C> f2,
final Function<C, D> f3
) {
return compose(compose(f1, f2), f3);
}
public static <A, B, C, D, E> Function<A, E> compose(
final Function<A, B> f1,
final Function<B, C> f2,
final Function<C, D> f3,
final Function<D, E> f4
) {
return compose(compose(compose(f1, f2), f3), f4);
}
public static <A, B, C, D, E, F> Function<A, F> compose(
final Function<A, B> f1,
final Function<B, C> f2,
final Function<C, D> f3,
final Function<D, E> f4,
final Function<E, F> f5
) {
return compose(compose(compose(compose(f1, f2), f3), f4), f5);
}
}