com.g2forge.alexandria.java.fluent.optional.AOptional Maven / Gradle / Ivy

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Standard Java library and the basis of the ${alexandria.name} project.

There is a newer version: 0.0.18

package com.g2forge.alexandria.java.fluent.optional;

import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;

import com.g2forge.alexandria.java.fluent.IFluent1_;

public abstract class AOptional implements IOptional {
	protected final T value;

	protected AOptional() {
		this.value = null;
	}

	protected AOptional(T value) {
		this.value = require(value);
	}

	protected abstract  AOptional create();

	protected  AOptional create(IFluent1_ value) {
		if (getClass().isInstance(value)) return (NonNullOptional) value;
		return value.isEmpty() ? create() : create(value.get());
	}

	protected abstract  AOptional create(U value);

	@Override
	public boolean equals(Object obj) {
		if (this == obj) { return true; }
		if (!(obj instanceof AOptional)) { return false; }

		final AOptional that = (AOptional) obj;
		return Objects.equals(isEmpty(), that.isEmpty()) && Objects.equals(value, that.value);
	}

	public AOptional filter(Predicate predicate) {
		Objects.requireNonNull(predicate);
		if (isEmpty()) return this;
		else return predicate.test(value) ? this : create();
	}

	public  IOptional flatMap(Function> mapper) {
		Objects.requireNonNull(mapper);
		if (isEmpty()) return create();
		else return create(Objects.requireNonNull(mapper.apply(value)));
	}

	public T get() {
		if (isEmpty()) {
			throw new NoSuchElementException("No value present");
		}
		return value;
	}

	@Override
	public int hashCode() {
		return Objects.hash(Boolean.valueOf(isEmpty()), value);
	}

	public  AOptional map(Function mapper) {
		Objects.requireNonNull(mapper);
		if (isEmpty()) return create();
		else return create(mapper.apply(value));
	}

	public T or(T other) {
		return isEmpty() ? other : value;
	}

	public T orGet(Supplier other) {
		return isEmpty() ? other.get() : value;
	}

	public  T orThrow(Supplier exception) throws X {
		if (isEmpty()) throw exception.get();
		else return value;
	}

	protected <_T> _T require(_T value) {
		return value;
	}

	@Override
	public String toString() {
		final String name = getClass().getSimpleName();
		return isEmpty() ? String.format("%s.empty", name) : String.format("%s[%s]", name, value);
	}

	public void visit(Consumer consumer) {
		if (!isEmpty()) consumer.accept(value);
	}
}