jdk/src/share/classes/java/util/function/LongUnaryOperator.java

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package java.util.function;

import java.util.Objects;

/**
 * An operation on a single {@code long} operand yielding a {@code long} result.
 * This is the primitive type specialization of {@link UnaryOperator} for
 * {@code long}.
 *
 * @see UnaryOperator
 * @since 1.8
 */
@FunctionalInterface
public interface LongUnaryOperator {

    /**
     * Returns the {@code long} result of the operation upon the {@code long}
     * operand.
     *
     * @param operand the operand value
     * @return the operation result value
     */
    long applyAsLong(long operand);

    /**
     * Compose a new function which applies the provided function followed by
     * this function.  If either function throws an exception, it is relayed
     * to the caller.
     *
     * @param before An additional function to be applied before this function
     * is applied
     * @return A function which performs the provided function followed by this
     * function
     * @throws NullPointerException if before is null
     */
    default LongUnaryOperator compose(LongUnaryOperator before) {
        Objects.requireNonNull(before);
        return (long v) -> applyAsLong(before.applyAsLong(v));
    }

    /**
     * Compose a new function which applies this function followed by the
     * provided function.  If either function throws an exception, it is relayed
     * to the caller.
     *
     * @param after An additional function to be applied after this function is
     * applied
     * @return A function which performs this function followed by the provided
     * function followed
     * @throws NullPointerException if after is null
     */
    default LongUnaryOperator andThen(LongUnaryOperator after) {
        Objects.requireNonNull(after);
        return (long t) -> after.applyAsLong(applyAsLong(t));
    }

    /**
     * Returns a unary operator that provides its input value as the result.
     *
     * @return a unary operator that provides its input value as the result
     */
    static LongUnaryOperator identity() {
        return t -> t;
    }
}