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package java.util.function;

import java.util.Objects;

/**
 * Represents an operation on a single {@code byte}-valued operand that produces
 * a {@code byte}-valued result. This is the primitive type specialization of
 * {@link UnaryOperator} for {@code byte}.
 * <p>
 * This is a <a href="package-summary.html">functional interface</a>
 * whose functional method is {@link #applyAsByte(byte)}.
 *
 * @see UnaryOperator
 * @author AqD
 */
@FunctionalInterface
public interface ByteUnaryOperator {

    /**
     * Applies this operator to the given operand.
     *
     * @param operand the operand
     * @return the operator result
     */
    byte applyAsByte(byte operand);

    /**
     * Returns a composed operator that first applies the {@code before}
     * operator to its input, and then applies this operator to the result.
     * If evaluation of either operator throws an exception, it is relayed to
     * the caller of the composed operator.
     *
     * @param before the operator to apply before this operator is applied
     * @return a composed operator that first applies the {@code before}
     *         operator and then applies this operator
     * @throws NullPointerException if before is null
     * @see #andThen(ByteUnaryOperator)
     */
    default ByteUnaryOperator compose(ByteUnaryOperator before) {
        Objects.requireNonNull(before);
        return (byte v) -> applyAsByte(before.applyAsByte(v));
    }

    /**
     * Returns a composed operator that first applies this operator to
     * its input, and then applies the {@code after} operator to the result.
     * If evaluation of either operator throws an exception, it is relayed to
     * the caller of the composed operator.
     *
     * @param after the operator to apply after this operator is applied
     * @return a composed operator that first applies this operator and then
     *         applies the {@code after} operator
     * @throws NullPointerException if after is null
     * @see #compose(ByteUnaryOperator)
     */
    default ByteUnaryOperator andThen(ByteUnaryOperator after) {
        Objects.requireNonNull(after);
        return (byte t) -> after.applyAsByte(applyAsByte(t));
    }

    /**
     * Returns a unary operator that always returns its input argument.
     *
     * @return a unary operator that always returns its input argument
     */
    static ByteUnaryOperator identity() {
        return t -> t;
    }
}