export declare class StringHelper {
    static firstUpper(v?: string | null): string | null | undefined;
    static isNullOrEmpty(value?: string | null): boolean;
    static isNullOrWhiteSpace(value?: string | null): boolean;
    static tryTrim(val: string | undefined | null): string | null | undefined;
    static ifNullEmpty(value?: string | null): string;
    static join(val: string | undefined | null, separator: string, part: string | undefined | null): string | null | undefined;
    static trim(val: string | null, ch: string): string | null;
    static trimStart(val: string | null, ch: string): string | null;
    static trimEnd(val: string | null, ch: string): string | null;
    /**
     *
     * @param val source string
     * @param chars trim any character
     * @returns
     */
    static trimAny(val: string | null, chars: string): string | null;
    static split(val: string | null | undefined, ...separator: string[]): string[];
}