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Java Simplified. Extensions and Useful Constructs for the Java Platform. Codeprimate Elements (a.k.a. cp-elements) is a Java library and micro-framework used to simplify the development of software applications written in Java. Elements packages several APIs into one library in order to address various application concerns and aspects of software design and development collectively and conveniently. Elements is a highly simple, yet robust and proven library built on solid OO principles, software design patterns and best practices to effectively solve common and reoccurring problems in software development.

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/*
 * Copyright 2016 Author or Authors.
 *
 * Licensed 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.cp.elements.data.struct;

import java.util.Optional;

import org.cp.elements.lang.concurrent.ThreadSafe;

/**
 * The {@link EnvironmentVariableValue} class is {@link KeyValue} data structure providing access to the value
 * of a given System environment variable.
 *
 * @author John Blum
 * @see java.lang.System#getenv()
 * @see org.cp.elements.data.struct.KeyValue
 * @since 1.0.0
 */
@ThreadSafe
@SuppressWarnings("unused")
public class EnvironmentVariableValue extends KeyValue {

  /**
   * Factory method used to construct a new instance of {@link EnvironmentVariableValue} initialized with
   * the given system environment variable.
   *
   * @param environmentVariable System environment variable.
   * @return a new instance of {@link EnvironmentVariableValue} initialized with the given system environment variable.
   * @throws IllegalArgumentException if environment variable is {@literal null}.
   * @see #EnvironmentVariableValue(String)
   */
  public static EnvironmentVariableValue newEnvironmentVariableValue(String environmentVariable) {
    return new EnvironmentVariableValue(environmentVariable);
  }

  /**
   * Constructs a new instance of {@link EnvironmentVariableValue} initialized with the given environment variable.
   *
   * @param environmentVariable System environment variable.
   * @throws IllegalArgumentException if environment variable is {@literal null}.
   */
  public EnvironmentVariableValue(String environmentVariable) {
    super(environmentVariable);
  }

  /**
   * Get the value of this environment variable as a {@literal null-safe} {@link Optional} value.
   *
   * @return the value of this environment variable as a {@literal null-safe} {@link Optional} value.
   * @see java.lang.System#getenv(String)
   * @see java.util.Optional
   */
  @Override
  public Optional getValue() {
    return Optional.ofNullable(System.getenv(getKey()));
  }
}