de.vandermeer.skb.interfaces.transformers.Transformer.java Source code

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Here is the source code for de.vandermeer.skb.interfaces.transformers.Transformer.java

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/* Copyright 2016 Sven van der Meer <vdmeer.sven@mykolab.com>
 *
 * 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 de.vandermeer.skb.interfaces.transformers;

import java.util.function.Function;
import java.util.function.Predicate;

import org.apache.commons.lang3.Validate;

/**
 * Standard transformer transforming FROM to TO with or with a predicate.
 *
 * @author     Sven van der Meer &lt;vdmeer.sven@mykolab.com&gt;
 * @version    v0.0.2 build 170502 (02-May-17) for Java 1.8
 * @since      v0.0.1
 */
public interface Transformer<FROM, TO> extends Function<FROM, TO> {

    /**
     * Transforms from one representation to another.
     * @param from input representation
     * @return output representation or null if input was null or unexpected class
     * @throws NullPointerException if the argument was null
     */
    default TO transform(FROM from) {
        Validate.notNull(from);
        return null;
    }

    @Override
    default TO apply(FROM from) {
        return transform(from);
    }

    /**
     * Transforms from one representation to another if a given predicate tests true.
     * @param from input representation
     * @param predicate predicate to apply to input before transformation
     * @return output representation or null if input was null or unexpected class
     * @throws NullPointerException if any argument was null
     */
    default TO transform(FROM from, Predicate<FROM> predicate) {
        Validate.notNull(from);
        Validate.notNull(predicate);

        if (predicate.test(from)) {
            return this.transform(from);
        }
        return null;
    }
}