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/**
 *  Copyright 2011 Alexandru Craciun, Eyal Kaspi
 *
 *  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.stjs.generator.utils;

import static java.lang.String.format;

import java.util.Iterator;
import java.util.NoSuchElementException;

public abstract class Option implements Iterable {

	/**
	 * The singleton representing none.
	 */
	private final static Option NONE = new Option() {

		@Override
		public Object getOrNull() {
			return null;
		};

		@Override
		public Object getOrElse(Object defaultValue) {
			return defaultValue;
		}

		@Override
		public Object getOrThrow() {
			return getOrThrow(new IllegalArgumentException());
		}

		@Override
		public Object getOrThrow(String message) {
			return getOrThrow(new IllegalArgumentException(message));
		}

		@Override
		public  Object getOrThrow(E e) throws E {
			throw e;
		}

		@Override
		public String toStringOr(String defaultValue) {
			return defaultValue;
		}

		@Override
		public boolean isEmpty() {
			return true;
		}

		@Override
		public int hashCode() {
			return 0;
		}

		@Override
		public boolean equals(Object that) {
			return this == that;
		}

		@Override
		public String toString() {
			return "Option.None";
		}

		@Override
		public Iterator iterator() {
			return new Iterator() {

				@Override
				public boolean hasNext() {
					return false;
				}

				@Override
				public Object next() {
					throw new NoSuchElementException();
				}

				@Override
				public void remove() {
					throw new NoSuchElementException();
				}
			};
		}

	};

	/**
	 * The object representing some result.
	 */
	private final static class Some extends Option {

		private final U u;

		private Some(U u) {
			super();
			PreConditions.checkNotNull(u);
			this.u = u;
		}

		@Override
		public U getOrNull() {
			return u;
		}

		@Override
		public U getOrElse(U defaultValue) {
			return u;
		}

		@Override
		public U getOrThrow() {
			return u;
		}

		@Override
		public U getOrThrow(String message) {
			return u;
		}

		@Override
		public  U getOrThrow(E e) throws E {
			return u;
		}

		@Override
		public String toStringOr(String defaultValue) {
			return u.toString();
		}

		@Override
		public boolean isEmpty() {
			return false;
		}

		@Override
		public int hashCode() {
			return u.hashCode();
		}

		@Override
		public boolean equals(Object that) {
			if (this == that) {
				return true;
			}
			if (!(that instanceof Some)) {
				return false;
			}
			return this.u.equals(((Some) that).u);
		}

		@Override
		public String toString() {
			return format("Option.Some(%s)", u);
		}

		@Override
		public Iterator iterator() {
			return new Iterator() {
				private boolean produce = true;

				@Override
				public boolean hasNext() {
					return produce;
				}

				@Override
				public U next() {
					if (produce) {
						produce = false;
						return u;
					}
					throw new NoSuchElementException();
				}

				@Override
				public void remove() {
					throw new NoSuchElementException();
				}
			};
		}

	}

	/**
	 * If the option is nonempty returns its value, otherwise returns {@code null}.
	 */
	public abstract T getOrNull();

	/**
	 * If the option is nonempty returns its value, otherwise returns {@code defaultValue}. Note that
	 * {@code defaultValue} is eagerly evaluated.
	 */
	public abstract T getOrElse(T defaultValue);

	/**
	 * Gets the value of this option. If this is a Some(T) the value is returned, otherwise an
	 * {@link IllegalArgumentException} is thrown.
	 */
	public abstract T getOrThrow();

	/**
	 * Gets the value of this option. If this is a Some(T) the value is returned, otherwise an
	 * {@link IllegalArgumentException} is thrown with the specifed message.
	 */
	public abstract T getOrThrow(String message);

	/**
	 * Returns its value if not empty, otherwise throws {@code e}.
	 */
	public abstract  T getOrThrow(E e) throws E;

	public abstract String toStringOr(String defaultValue);

	/**
	 * Returns {@code true} if the option is the {@code None} value.
	 */
	public abstract boolean isEmpty();

	/**
	 * Returns {@code true} if the option is a {@code Some(...)}.
	 */
	public boolean isDefined() {
		return !isEmpty();
	}

	/**
	 * Gets the none object for the given type. Note: using a freely parameterized type {@code T} with an unchecked
	 * warning allows to simulate a bottom type in Java.
	 */
	@SuppressWarnings("unchecked")
	public static  Option none() {
		return (Option) NONE;
	}

	/**
	 * Gets the some object wrapping the given value.
	 */
	public static  Option some(T t) {
		return new Option.Some(t);
	}

	/**
	 * Wraps anything.
	 * 
	 * @param 
	 * @param t
	 * @return if null, none(), some(t) otherwise
	 */
	public static  Option of(T t) {
		return t == null ? Option.none() : some(t);
	}
}
    

    

    

            

    

            



    
    






    
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