Java - Write code to Remove given char if it pre-fixes the given string

Requirements

Write code to Remove given char if it pre-fixes the given string
Demo

/*
 * Copyright 2013 Kay Stenschke// w  w  w  . j  a v a2 s .  c o  m
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
//package com.book2s;

public class Main {
    public static void main(String[] argv) {
        String sourceStr = "book2s.com";
        String prefixChar = "b";
        System.out.println(removePrefixChar(sourceStr, prefixChar));
    }

    /**
     * Remove given char if it pre-fixes the given string
     *
     * @param   sourceStr
     * @param   prefixChar
     * @param   prefixMustExist   true: if prefix isn't the given one: return null / otherwise return as is
     * @return   String
     */
    private static String removePrefixChar(String sourceStr,
            String prefixChar, Boolean prefixMustExist) {
        if (sourceStr != null && sourceStr.indexOf(prefixChar) == 0) {
            return sourceStr.substring(1);
        }

        return prefixMustExist ? null : sourceStr;
    }

    private static String removePrefixChar(String sourceStr,
            String prefixChar) {
        return removePrefixChar(sourceStr, prefixChar, true);
    }
}