content: /*
   * 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.beam.sdk.util;
  
  import org.apache.beam.sdk.annotations.Internal;
  
  /**
   * A trivial boxing of a value, used when nullability needs to be added to a generic type. (Optional
   * does not work for this)
   *
   * <p>Example: For a generic type `T` the actual parameter may be nullable or not. So you cannot
   * check values for null to determine presence/absence. Instead you can store a {@code @Nullable
   * Holder<T>}.
   */
  @Internal
  public class Holder<T> {
    private T value;
  
    private Holder(T value) {
      this.value = value;
    }
  
    public static <ValueT> Holder<ValueT> of(ValueT value) {
      return new Holder<>(value);
    }
  
    public T get() {
      return value;
    };
  }
  