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

  /**
   * Factory method used to construct a new instance of {@link SystemPropertyValue} initialized with
   * the given system property.
   *
   * @param systemProperty Java system property.
   * @return a new instance of the {@link SystemPropertyValue} initialized with the given system property.
   * @throws IllegalArgumentException if system property is {@literal null}.
   * @see #SystemPropertyValue(String)
   */
  public static SystemPropertyValue newSystemPropertyValue(String systemProperty) {
    return new SystemPropertyValue(systemProperty);
  }

  /**
   * Constructs a new instance of {@link SystemPropertyValue} initialized with the given system property.
   *
   * @param systemProperty Java system property.
   * @throws IllegalArgumentException if system property is {@literal null}.
   */
  public SystemPropertyValue(String systemProperty) {
    super(systemProperty);
  }

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