export declare class StringUtil {
    static isNotBlank(stringToCheck: string | undefined | null): boolean;
    static isBlank(stringToCheck: string | undefined | null): boolean;
    static requireNonBlank(stringToCheck: string | undefined | null, message: string): void;
    static isPositiveInteger(value: string): boolean;
    static isNonNegativeInteger(value: string): boolean;
}