io.github.oliviercailloux.jaris.throwing.TOptional Maven / Gradle / Ivy
package io.github.oliviercailloux.jaris.throwing;
import io.github.oliviercailloux.jaris.exceptions.Throwing;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.Optional;
import java.util.stream.Stream;
/**
* An enhanced version of {@link Optional}, with methods that accept throwing functionals.
*
* Much of the code and documentation here has been adapted from the OpenJDK specification and
* implementation of {@link Optional}.
*
* TODO adapt doc and check signatures.
*
* @param the type of value
* @see Optional
*/
@SuppressWarnings("checkstyle:AbbreviationAsWordInName")
public class TOptional {
/**
* Common instance for {@code empty()}.
*/
private static final TOptional EMPTY = new TOptional<>(null);
public static TOptional wrapping(Optional delegate) {
return delegate.>map(TOptional::of).orElse(empty());
}
/**
* Returns an empty {@code TOptional} instance.
*
* @param The type of the non-existent value
* @return an empty {@code TOptional}
*/
public static TOptional empty() {
@SuppressWarnings("unchecked")
final TOptional t = (TOptional) EMPTY;
return t;
}
/**
* Returns a {@code TOptional} describing the given non-{@code null} value.
*
* @param value the value to describe, which must be non-{@code null}
* @param the type of the value
* @return a {@code TOptional} with the value present
* @throws NullPointerException if value is {@code null}
*/
public static TOptional of(T value) {
return new TOptional<>(Objects.requireNonNull(value));
}
/**
* Returns a {@code TOptional} describing the given value, if non-{@code null}, otherwise returns
* an empty {@code TOptional}.
*
* @param value the possibly-{@code null} value to describe
* @param the type of the value
* @return a {@code TOptional} with a present value if the specified value is non-{@code null},
* otherwise an empty {@code TOptional}
*/
public static TOptional ofNullable(T value) {
return value == null ? empty() : new TOptional<>(value);
}
private T value;
/**
* Constructs an instance with the described value.
*
* @param value {@code null} iff empty.
*/
private TOptional(T value) {
this.value = value;
}
/**
* If a value is present, returns {@code true}, otherwise {@code false}.
*
* @return {@code true} if a value is present, otherwise {@code false}
*/
public boolean isPresent() {
return value != null;
}
/**
* If a value is not present, returns {@code true}, otherwise {@code false}.
*
* @return {@code true} if a value is not present, otherwise {@code false}
*/
public boolean isEmpty() {
return value == null;
}
/**
* If a value is present, performs the given action with the value, otherwise does nothing.
*
* @param action the action to be performed, if a value is present
* @throws NullPointerException if value is present and the given action is {@code null}
*/
public void ifPresent(Throwing.Consumer action) throws X {
if (value != null) {
action.accept(value);
}
}
/**
* If a value is present, performs the given action with the value, otherwise performs the given
* empty-based action.
*
* @param action the action to be performed, if a value is present
* @param emptyAction the empty-based action to be performed, if no value is present
* @throws NullPointerException if a value is present and the given action is {@code null}, or no
* value is present and the given empty-based action is {@code null}.
*/
public void ifPresentOrElse(
Throwing.Consumer action, Throwing.Runnable emptyAction)
throws X {
if (value != null) {
action.accept(value);
} else {
emptyAction.run();
}
}
/**
* If a value is present, and the value matches the given predicate, returns an {@code Optional}
* describing the value, otherwise returns an empty {@code Optional}.
*
* @param predicate the predicate to apply to a value, if present
* @return an {@code Optional} describing the value of this {@code Optional}, if a value is
* present and the value matches the given predicate, otherwise an empty {@code Optional}
* @throws NullPointerException if the predicate is {@code null}
*/
public TOptional filter(Throwing.Predicate predicate)
throws X {
Objects.requireNonNull(predicate);
if (!isPresent()) {
return this;
}
return predicate.test(value) ? this : empty();
}
/**
* If a value is present, returns an {@code Optional} describing (as if by {@link #ofNullable})
* the result of applying the given mapping function to the value, otherwise returns an empty
* {@code Optional}.
*
*
* If the mapping function returns a {@code null} result then this method returns an empty
* {@code Optional}.
*
* @param mapper the mapping function to apply to a value, if present
* @param The type of the value returned from the mapping function
* @return an {@code Optional} describing the result of applying a mapping function to the value
* of this {@code Optional}, if a value is present, otherwise an empty {@code Optional}
* @throws NullPointerException if the mapping function is {@code null}
*/
public TOptional
map(Throwing.Function mapper) throws X {
Objects.requireNonNull(mapper);
if (!isPresent()) {
return empty();
}
return TOptional.ofNullable(mapper.apply(value));
}
/**
* If a value is present, returns the result of applying the given {@code Optional}-bearing
* mapping function to the value, otherwise returns an empty {@code Optional}.
*
* @param The type of value of the {@code Optional} returned by the mapping function
* @param mapper the mapping function to apply to a value, if present
* @return the result of applying an {@code Optional}-bearing mapping function to the value of
* this {@code Optional}, if a value is present, otherwise an empty {@code Optional}
* @throws NullPointerException if the mapping function is {@code null} or returns a {@code null}
* result
*/
public TOptional
flatMap(Throwing.Function, X> mapper) throws X {
Objects.requireNonNull(mapper);
if (!isPresent()) {
return empty();
}
@SuppressWarnings("unchecked")
final TOptional r = (TOptional) mapper.apply(value);
return Objects.requireNonNull(r);
}
/**
* If a value is present, returns an {@code Optional} describing the value, otherwise returns an
* {@code Optional} produced by the supplying function.
*
* @param supplier the supplying function that produces an {@code Optional} to be returned
* @return returns an {@code Optional} describing the value of this {@code Optional}, if a value
* is present, otherwise an {@code Optional} produced by the supplying function.
* @throws NullPointerException if the supplying function is {@code null} or produces a
* {@code null} result
*/
public TOptional
or(Throwing.Supplier, X> supplier) throws X {
Objects.requireNonNull(supplier);
if (isPresent()) {
return this;
}
@SuppressWarnings("unchecked")
final TOptional r = (TOptional) supplier.get();
return Objects.requireNonNull(r);
}
/**
* If a value is present, returns a sequential {@link Stream} containing only that value,
* otherwise returns an empty {@code Stream}.
*
* @return the optional value as a {@code Stream}
*/
public Stream stream() {
if (!isPresent()) {
return Stream.empty();
}
return Stream.of(value);
}
/**
* If a value is present, returns the value, otherwise returns {@code other}.
*
* @param other the value to be returned, if no value is present. May be {@code null}.
* @return the value, if present, otherwise {@code other}
*/
public T orElse(T other) {
return value != null ? value : other;
}
/**
* If a value is present, returns the value, otherwise returns the result produced by the
* supplying function.
*
* @param supplier the supplying function that produces a value to be returned
* @return the value, if present, otherwise the result produced by the supplying function
* @throws NullPointerException if no value is present and the supplying function is {@code null}
*/
public T orElseGet(Throwing.Supplier supplier) throws X {
return value != null ? value : supplier.get();
}
/**
* If a value is present, returns the value, otherwise throws {@code NoSuchElementException}.
*
* @return the non-{@code null} value described by this {@code Optional}
* @throws NoSuchElementException if no value is present
*/
public T orElseThrow() {
if (value == null) {
throw new NoSuchElementException("No value present");
}
return value;
}
/**
* If a value is present, returns the value, otherwise throws an exception produced by the
* exception supplying function.
*
* @param Type of the exception to be thrown
* @param exceptionSupplier the supplying function that produces an exception to be thrown
* @return the value, if present
* @throws X if no value is present
* @throws NullPointerException if no value is present and the exception supplying function is
* {@code null}
*/
public T
orElseThrow(Throwing.Supplier exceptionSupplier) throws X, Y {
if (value != null) {
return value;
}
throw exceptionSupplier.get();
}
/**
* Indicates whether some other object is "equal to" this {@code Optional}. The other object is
* considered equal if:
*
* - it is also an {@code Optional} and;
*
- both instances have no value present or;
*
- the present values are "equal to" each other via {@code equals()}.
*
*
* @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;
}
return obj instanceof TOptional other && Objects.equals(value, other.value);
}
/**
* Returns the hash code of the value, if present, otherwise {@code 0} (zero) if no value is
* present.
*
* @return hash code value of the present value or {@code 0} if no value is present
*/
@Override
public int hashCode() {
return Objects.hashCode(value);
}
/**
* Returns a non-empty string representation of this {@code Optional} suitable for debugging. The
* exact presentation format is unspecified and may vary between implementations and versions.
*
* @return the string representation of this instance
*/
@Override
public String toString() {
return value != null ? String.format("Optional[%s]", value) : "Optional.empty";
}
}