package org.lsst.ccs.utilities.beanutils;
   
   import java.util.NoSuchElementException;
   import java.util.Objects;
   
   /**
    * a Pre-java8 optional class to be replaced by java8 when needed.
    *
    * @author bamade
   */
  // Date: 09/12/2013
  
  public class Optional<T> {
      private static final Optional<?> EMPTY = new Optional<>();
  
      /**
       * If non-null, the value; if null, indicates no value is present
       */
      private final T value;
  
      private Optional() {
          this.value = null;
      }
  
      public static <T> Optional<T> empty() {
          @SuppressWarnings("unchecked")
          Optional<T> t = (Optional<T>) EMPTY;
          return t;
      }
  
      private Optional(T value) {
          this.value = Objects.requireNonNull(value);
      }
  
      public static <T> Optional<T> of(T value) {
          return new Optional<>(value);
      }
  
      public static <T> Optional<T> ofNullable(T value) {
          if (value == null) {
              return empty();
          }
          return of(value);
      }
  
      public T get() {
          if (value == null) {
              throw new NoSuchElementException("No value present");
          }
          return value;
      }
  
      public boolean isPresent() {
          return value != null;
      }
  
      public T orElse(T other) {
          return value != null ? value : other;
      }
  
      @Override
      public boolean equals(Object obj) {
          if (this == obj) {
              return true;
          }
  
          if (!(obj instanceof Optional)) {
              return false;
          }
  
          Optional<?> other = (Optional<?>) obj;
          return Objects.equals(value, other.value);
      }
  
      @Override
      public int hashCode() {
          return Objects.hashCode(value);
      }
  
  
      @Override
      public String toString() {
          return value != null
                  ? String.format("Optional[%s]", value)
                  : "Optional.empty";
      }
  
  
  }