使用String類的indexOf()和subString方法犯了一個低級的錯誤

     今天在公司開發，在使用String類的字符串操做函數的時候犯了一個比較低級的錯誤。緣由是本身對substring()方法以及indexOf()方法的使用瞭解的不夠深刻。
     錯誤的代碼以下：String frpName = frpName.substring(0, frpName.indexOf("("));用處是：當字符串後面包含(),就將()去掉。由於少判斷了indexOf("(")等於-1的狀況，因此程序編譯沒有出錯，卻在運行的時候致使系統出現了問題。
兩個函數的源代碼以下：

public int indexOf(String str, int fromIndex) {
        return indexOf(value, offset, count,
                       str.value, str.offset, str.count, fromIndex);
    }
 
    //source源字符，sourceOffset源偏移，sourceCount源長度
    //target查找的字符 ...
    static int indexOf(char[] source, int sourceOffset, int sourceCount,
                       char[] target, int targetOffset, int targetCount,
                       int fromIndex) {
        //若是fromIndex比源字符還長(從0算起)，而且查找的字符長度爲0，那就返回源字符的長度，不然返回-1
	if (fromIndex >= sourceCount) {
            return (targetCount == 0 ? sourceCount : -1);
	}
    	if (fromIndex < 0) {
    	    fromIndex = 0;
    	}
        //若是fromIndex比源字符短，查找的字符長度爲0，直接返回fromIndex
	if (targetCount == 0) {
	    return fromIndex;
	}
 
        //先取出第一個字符
        char first  = target[targetOffset];
        int max = sourceOffset + (sourceCount - targetCount);
 
        //循環每個字符
        for (int i = sourceOffset + fromIndex; i <= max; i++) {
            /* 直到找到第一個字符 */
            if (source[i] != first) {
                while (++i <= max && source[i] != first);
            }
 
            /* 找到第一個字符後，比較剩下的字符 */
            if (i <= max) {
                int j = i + 1;
                int end = j + targetCount - 1;
                for (int k = targetOffset + 1; j < end && source[j] ==
                         target[k]; j++, k++);
 
                if (j == end) {
                    /* 若是j能到end，那就說明找到整個字符串啦，返回偏移 */
                    return i - sourceOffset;
                }
            }
        }
        return -1;
    }

/**
     * Returns a new string that is a substring of this string. The
     * substring begins at the specified <code>beginIndex</code> and
     * extends to the character at index <code>endIndex - 1</code>.
     * Thus the length of the substring is <code>endIndex-beginIndex</code>.
     * <p>
     * Examples:
     * <blockquote><pre>
     * "hamburger".substring(4, 8) returns "urge"
     * "smiles".substring(1, 5) returns "mile"
     * </pre></blockquote>
     *
     * @param      beginIndex   the beginning index, inclusive.
     * @param      endIndex     the ending index, exclusive.
     * @return     the specified substring.
     * @exception  IndexOutOfBoundsException  if the
     *             <code>beginIndex</code> is negative, or
     *             <code>endIndex</code> is larger than the length of
     *             this <code>String</code> object, or
     *             <code>beginIndex</code> is larger than
     *             <code>endIndex</code>.
     */
    public String substring(int beginIndex, int endIndex) {
	if (beginIndex < 0) {
	    throw new StringIndexOutOfBoundsException(beginIndex);
	}
	if (endIndex > count) {
	    throw new StringIndexOutOfBoundsException(endIndex);
	}
	if (beginIndex > endIndex) {
	    throw new StringIndexOutOfBoundsException(endIndex - beginIndex);
	}
	return ((beginIndex == 0) && (endIndex == count)) ? this :
	    new String(offset + beginIndex, endIndex - beginIndex, value);
    }