statefun-flink/statefun-flink-core/src/main/java/org/apache/flink/statefun/flink/core/common/Maps.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.flink.statefun.flink.core.common;

import java.util.HashMap;
import java.util.Map;
import java.util.function.BiFunction;
import java.util.function.Function;

public final class Maps {
  private Maps() {}

  public static <K, V, U> Map<K, U> transformValues(Map<K, V> map, Function<V, U> fn) {
    Map<K, U> result = new HashMap<>();

    for (Map.Entry<K, V> entry : map.entrySet()) {
      U u = fn.apply(entry.getValue());
      result.put(entry.getKey(), u);
    }

    return result;
  }

  public static <K, V, U> Map<U, V> transformKeys(Map<K, V> map, Function<K, U> fn) {
    Map<U, V> result = new HashMap<>(map.size());

    for (Map.Entry<K, V> entry : map.entrySet()) {
      U u = fn.apply(entry.getKey());
      result.put(u, entry.getValue());
    }

    return result;
  }

  public static <K, V, U> Map<K, U> transformValues(Map<K, V> map, BiFunction<K, V, U> fn) {
    Map<K, U> result = new HashMap<>();

    for (Map.Entry<K, V> entry : map.entrySet()) {
      U u = fn.apply(entry.getKey(), entry.getValue());
      result.put(entry.getKey(), u);
    }

    return result;
  }

  public static <K, T> Map<K, T> index(Iterable<T> elements, Function<T, K> indexBy) {
    Map<K, T> index = new HashMap<>();
    for (T element : elements) {
      index.put(indexBy.apply(element), element);
    }
    return index;
  }
}