/*
* Copyright 2015 MongoDB, Inc.
*
* 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.bson.codecs.configuration;
import java.util.NoSuchElementException;
abstract class Optional<T> {
private static final Optional<Object> NONE = new Optional<Object>() {
@Override
public Object get() {
throw new NoSuchElementException(".get call on None!");
}
@Override
public boolean isEmpty() {
return true;
}
};
@SuppressWarnings("unchecked")
public static <T> Optional<T> empty() {
return (Optional<T>) NONE;
}
@SuppressWarnings("unchecked")
public static <T> Optional<T> of(final T it) {
if (it == null) {
return (Optional<T>) Optional.NONE;
} else {
return new Some<T>(it);
}
}
public abstract T get();
public abstract boolean isEmpty();
@Override
public String toString() {
return "None";
}
public boolean isDefined() {
return !isEmpty();
}
public static class Some<T> extends Optional<T> {
private final T value;
Some(final T value) {
this.value = value;
}
@Override
public T get() {
return value;
}
@Override
public boolean isEmpty() {
return false;
}
@Override
public String toString() {
return String.format("Some(%s)", value);
}
}
}