@Override
    public boolean hasNext(int startPosition, int contentLength) {
        byte b = readByte();
        if (b == SIGN_HASNEXT) return true;
        if (b != SIGN_NONEXT) throw new ConvertException("hasNext option must be (" + (SIGN_HASNEXT)
                + " or " + (SIGN_NONEXT) + ") but '" + b + "' at position(" + this.position + ")");
        return false;
    }
@ Override public boolean hasNext ( int startPosition , int contentLength ) { byte b = readByte ( ) ; if ( b == SIGN_HASNEXT ) return true ; if ( b != SIGN_NONEXT ) throw new ConvertException ( "hasNext option must be (" + ( SIGN_HASNEXT ) + " or " + ( SIGN_NONEXT ) + ") but '" + b + "' at position(" + this . position + ")" ) ; return false ; }
判断对象是否存在下一个属性或者数组是否存在下一个元素

@param startPosition 起始位置
@param contentLength 内容大小， 不确定的传-1

@return 是否存在