package com.jiang.android.architecture.utils;

import android.support.annotation.Nullable;

final class Preconditions {

    /**
     * Ensures that an object reference passed as a parameter to the calling method is not null.
     *
     * @param reference an object reference
     * @return the non-null reference that was validated
     * @throws NullPointerException if {@code reference} is null
     */
    static <T> T checkNotNull(T reference) {
        if (reference == null) {
            throw new NullPointerException();
        }
        return reference;
    }

    /**
     * Ensures that an object reference passed as a parameter to the calling method is not null.
     *
     * @param reference    an object reference
     * @param errorMessage the exception message to use if the check fails; will be converted to a
     *                     string using {@link String#valueOf(Object)}
     * @return the non-null reference that was validated
     * @throws NullPointerException if {@code reference} is null
     */
    static <T> T checkNotNull(T reference, @Nullable Object errorMessage) {
        if (reference == null) {
            throw new NullPointerException(String.valueOf(errorMessage));
        }
        return reference;
    }
}
