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package org.uic.barcode.asn1.datatypes;
import java.util.NoSuchElementException;
import java.util.Objects;
/** Represents optional values.
*
* Should be replaced by java.util.Optional from Java 8, when project moves to Java 8.
*
* @param <T> type of contained elements */
public class Optional<T> {
private final T element;
private final boolean isPresent;
private Optional(T element, boolean isPresent) {
this.element = element;
this.isPresent = isPresent;
}
/** @return true if the Option contains a value */
public boolean isPresent() {
return isPresent;
}
/** @return the element if the option is not empty
* @throws java.util.NoSuchElementException if the option is empty */
public T get() {
if (isPresent) {
return element;
} else {
throw new NoSuchElementException("None.get");
}
}
/** @return the value, if present, otherwise return {@code other}
* @param other the value to be returned if there is no value present */
public T orElse(T other) {
return isPresent() ? get() : other;
}
/**
* Indicates whether some other object is "equal to" this Optional. The
* other object is considered equal if:
* <ul>
* <li>it is also an {@code Optional} and;
* <li>both instances have no value present or;
* <li>the present values are "equal to" each other via {@code equals()}.
* </ul>
*
* @param obj an object to be tested for equality
* @return {code true} if the other object is "equal to" this object
* otherwise {@code false}
*/
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (!(obj instanceof Optional)) {
return false;
}
Optional<?> other = (Optional<?>) obj;
return Objects.equals(element, other.element);
}
/**
* Returns the hash code value of the present value, if any, or 0 (zero) if
* no value is present.
*
* @return hash code value of the present value or 0 if no value is present
*/
@Override
public int hashCode() {
return Objects.hashCode(element);
}
/** Returns an Option containing the value.
*
* @param <A> the type of the value
* @param element contained value
* @return a new Option that contains the value */
public static <A> Optional<A> of(final A element) {
return new Optional<A>(element, true);
}
/** Returns an empty option.
*
* @param <A>
* @return an empty Option */
public static <A> Optional<A> empty() {
return new Optional<A>(null, false);
}
}
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