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Java example source code file (TransformerMap.java)

This example Java source code file (TransformerMap.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

collection, defaulttransformer, hashmap, mathillegalargumentexception, numbertransformer, override, serializable, set, string, transformermap, util

The TransformerMap.java Java example source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.math3.util;

import java.io.Serializable;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

import org.apache.commons.math3.exception.MathIllegalArgumentException;

/**
 * This TansformerMap automates the transformation of mixed object types.
 * It provides a means to set NumberTransformers that will be selected
 * based on the Class of the object handed to the Maps
 * <code>double transform(Object o) method.
 */
public class TransformerMap implements NumberTransformer, Serializable {

    /** Serializable version identifier */
    private static final long serialVersionUID = 4605318041528645258L;

    /**
     * A default Number Transformer for Numbers and numeric Strings.
     */
    private NumberTransformer defaultTransformer = null;

    /**
     * The internal Map.
     */
    private Map<Class map = null;

    /**
     * Build a map containing only the default transformer.
     */
    public TransformerMap() {
        map = new HashMap<Class();
        defaultTransformer = new DefaultTransformer();
    }

    /**
     * Tests if a Class is present in the TransformerMap.
     * @param key Class to check
     * @return true|false
     */
    public boolean containsClass(Class<?> key) {
        return map.containsKey(key);
    }

    /**
     * Tests if a NumberTransformer is present in the TransformerMap.
     * @param value NumberTransformer to check
     * @return true|false
     */
    public boolean containsTransformer(NumberTransformer value) {
        return map.containsValue(value);
    }

    /**
     * Returns the Transformer that is mapped to a class
     * if mapping is not present, this returns null.
     * @param key The Class of the object
     * @return the mapped NumberTransformer or null.
     */
    public NumberTransformer getTransformer(Class<?> key) {
        return map.get(key);
    }

    /**
     * Sets a Class to Transformer Mapping in the Map. If
     * the Class is already present, this overwrites that
     * mapping.
     * @param key The Class
     * @param transformer The NumberTransformer
     * @return the replaced transformer if one is present
     */
    public NumberTransformer putTransformer(Class<?> key, NumberTransformer transformer) {
        return map.put(key, transformer);
    }

    /**
     * Removes a Class to Transformer Mapping in the Map.
     * @param key The Class
     * @return the removed transformer if one is present or
     * null if none was present.
     */
    public NumberTransformer removeTransformer(Class<?> key) {
        return map.remove(key);
    }

    /**
     * Clears all the Class to Transformer mappings.
     */
    public void clear() {
        map.clear();
    }

    /**
     * Returns the Set of Classes used as keys in the map.
     * @return Set of Classes
     */
    public Set<Class classes() {
        return map.keySet();
    }

    /**
     * Returns the Set of NumberTransformers used as values
     * in the map.
     * @return Set of NumberTransformers
     */
    public Collection<NumberTransformer> transformers() {
        return map.values();
    }

    /**
     * Attempts to transform the Object against the map of
     * NumberTransformers. Otherwise it returns Double.NaN.
     *
     * @param o the Object to be transformed.
     * @return the double value of the Object.
     * @throws MathIllegalArgumentException if the Object can not be
     * transformed into a Double.
     * @see org.apache.commons.math3.util.NumberTransformer#transform(java.lang.Object)
     */
    public double transform(Object o) throws MathIllegalArgumentException {
        double value = Double.NaN;

        if (o instanceof Number || o instanceof String) {
            value = defaultTransformer.transform(o);
        } else {
            NumberTransformer trans = getTransformer(o.getClass());
            if (trans != null) {
                value = trans.transform(o);
            }
        }

        return value;
    }

    /** {@inheritDoc} */
    @Override
    public boolean equals(Object other) {
        if (this == other) {
            return true;
        }
        if (other instanceof TransformerMap) {
            TransformerMap rhs = (TransformerMap) other;
            if (! defaultTransformer.equals(rhs.defaultTransformer)) {
                return false;
            }
            if (map.size() != rhs.map.size()) {
                return false;
            }
            for (Map.Entry<Class entry : map.entrySet()) {
                if (! entry.getValue().equals(rhs.map.get(entry.getKey()))) {
                    return false;
                }
            }
            return true;
        }
        return false;
    }

    /** {@inheritDoc} */
    @Override
    public int hashCode() {
        int hash = defaultTransformer.hashCode();
        for (NumberTransformer t : map.values()) {
            hash = hash * 31 + t.hashCode();
        }
        return hash;
    }

}

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