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

Requirements

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

Demo

/*
 * Copyright 2013 Kay Stenschke/* w  ww  . j av a  2  s. c om*/
 *
 * 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 trailChar = "com";
        System.out.println(removePostfixChar(sourceStr, trailChar));
    }

    /**
     * Remove given char if it post-fixes the given string
     *
     * @param   sourceStr
     * @param   trailChar
     * @param   trailMustExist   true: if trail isn't the given one: return null / otherwise return as is
     * @return   String
     */
    private static String removePostfixChar(String sourceStr,
            String trailChar, Boolean trailMustExist) {
        if (sourceStr != null
                && sourceStr.lastIndexOf(trailChar) == sourceStr.length() - 1) {
            return sourceStr.substring(0, sourceStr.length() - 1);
        }

        return trailMustExist ? null : sourceStr;
    }

    private static String removePostfixChar(String sourceStr,
            String trailChar) {
        return removePostfixChar(sourceStr, trailChar, true);
    }
}