src/main/java/org/apache/commons/exec/util/MapUtils.java

/*
 * 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.exec.util;

import java.util.HashMap;
import java.util.Map;

/**
 * Helper classes to manipulate maps to pass substition map to the CommandLine. This class is not part of the public API
 * and could change without warning.
 *
 */
public class MapUtils
{
    /**
     * Clones a map.
     *
     * @param source
     *            the Map to clone
     * @param <K>
     *            the map key type
     * @param <V>
     *            the map value type
     * @return the cloned map
     */
   public static <K, V> Map<K, V> copy(final Map<K, V> source) {

        if (source == null) {
            return null;
        }

        final Map<K, V> result = new HashMap<>();
        result.putAll(source);
        return result;
    }

    /**
     * Clones a map and prefixes the keys in the clone, e.g. for mapping "JAVA_HOME" to "env.JAVA_HOME" to simulate the
     * behavior of Ant.
     *
     * @param source
     *            the source map
     * @param prefix
     *            the prefix used for all names
     * @param <K>
     *            the map key type
     * @param <V>
     *            the map value type
     * @return the clone of the source map
     */
    public static <K, V> Map<String, V> prefix(final Map<K, V> source, final String prefix) {

        if (source == null) {
            return null;
        }

        final Map<String, V> result = new HashMap<>();

        for (final Map.Entry<K, V> entry : source.entrySet()) {
            final K key = entry.getKey();
            final V value = entry.getValue();
            result.put(prefix + '.' + key.toString(), value);
        }

        return result;
    }

    /**
     * Clones the lhs map and add all things from the rhs map.
     *
     * @param lhs
     *            the first map
     * @param rhs
     *            the second map
     * @param <K>
     *            the map key type
     * @param <V>
     *            the map value type
     * @return the merged map
     */
    public static <K, V> Map<K, V> merge(final Map<K, V> lhs, final Map<K, V> rhs) {

        Map<K, V> result = null;

        if (lhs == null || lhs.isEmpty()) {
            result = copy(rhs);
        }
        else if (rhs == null || rhs.isEmpty()) {
            result = copy(lhs);
        }
        else {
            result = copy(lhs);
            result.putAll(rhs);
        }

        return result;
    }
}