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
 *
 *   https://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;
import java.util.Objects;

/**
 * Helper classes to manipulate maps to pass substitution 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) {
        return source == null ? null : new HashMap<>(source);
    }

    /**
     * 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;
    }

    /**
     * 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()) {
            result.put(prefix + '.' + Objects.toString(entry.getKey(), ""), entry.getValue());
        }
        return result;
    }

    /**
     * Constructs a new instance.
     *
     * @deprecated Will be private in the next major version.
     */
    @Deprecated
    public MapUtils() {
        // empty
    }
}