/**
* Licensed to jclouds, Inc. (jclouds) under one or more
* contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. jclouds 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.jclouds.util;
import static com.google.common.base.Preconditions.checkNotNull;
import java.util.Map;
import java.util.Map.Entry;
import com.google.common.base.Function;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableMap.Builder;
/**
* General utilities used in jclouds code for {@link Map Maps}.
*
* @author Adrian Cole
*/
public class Maps2 {
/**
* change the keys but keep the values in-tact.
*
* @param <K1>
* input key type
* @param <K2>
* output key type
* @param <V>
* value type
* @param in
* input map to transform
* @param fn
* how to transform the values
* @return immutableMap with the new keys.
*/
public static <K1, K2, V> Map<K2, V> transformKeys(Map<K1, V> in, Function<K1, K2> fn) {
checkNotNull(in, "input map");
checkNotNull(fn, "function");
Builder<K2, V> returnVal = ImmutableMap.builder();
for (Entry<K1, V> entry : in.entrySet())
returnVal.put(fn.apply(entry.getKey()), entry.getValue());
return returnVal.build();
}
}