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  • C#: String Concatenation vs Format vs StringBuilder

    - by James Michael Hare
    I was looking through my groups’ C# coding standards the other day and there were a couple of legacy items in there that caught my eye.  They had been passed down from committee to committee so many times that no one even thought to second guess and try them for a long time.  It’s yet another example of how micro-optimizations can often get the best of us and cause us to write code that is not as maintainable as it could be for the sake of squeezing an extra ounce of performance out of our software. So the two standards in question were these, in paraphrase: Prefer StringBuilder or string.Format() to string concatenation. Prefer string.Equals() with case-insensitive option to string.ToUpper().Equals(). Now some of you may already know what my results are going to show, as these items have been compared before on many blogs, but I think it’s always worth repeating and trying these yourself.  So let’s dig in. The first test was a pretty standard one.  When concattenating strings, what is the best choice: StringBuilder, string concattenation, or string.Format()? So before we being I read in a number of iterations from the console and a length of each string to generate.  Then I generate that many random strings of the given length and an array to hold the results.  Why am I so keen to keep the results?  Because I want to be able to snapshot the memory and don’t want garbage collection to collect the strings, hence the array to keep hold of them.  I also didn’t want the random strings to be part of the allocation, so I pre-allocate them and the array up front before the snapshot.  So in the code snippets below: num – Number of iterations. strings – Array of randomly generated strings. results – Array to hold the results of the concatenation tests. timer – A System.Diagnostics.Stopwatch() instance to time code execution. start – Beginning memory size. stop – Ending memory size. after – Memory size after final GC. So first, let’s look at the concatenation loop: 1: // build num strings using concattenation. 2: for (int i = 0; i < num; i++) 3: { 4: results[i] = "This is test #" + i + " with a result of " + strings[i]; 5: } Pretty standard, right?  Next for string.Format(): 1: // build strings using string.Format() 2: for (int i = 0; i < num; i++) 3: { 4: results[i] = string.Format("This is test #{0} with a result of {1}", i, strings[i]); 5: }   Finally, StringBuilder: 1: // build strings using StringBuilder 2: for (int i = 0; i < num; i++) 3: { 4: var builder = new StringBuilder(); 5: builder.Append("This is test #"); 6: builder.Append(i); 7: builder.Append(" with a result of "); 8: builder.Append(strings[i]); 9: results[i] = builder.ToString(); 10: } So I take each of these loops, and time them by using a block like this: 1: // get the total amount of memory used, true tells it to run GC first. 2: start = System.GC.GetTotalMemory(true); 3:  4: // restart the timer 5: timer.Reset(); 6: timer.Start(); 7:  8: // *** code to time and measure goes here. *** 9:  10: // get the current amount of memory, stop the timer, then get memory after GC. 11: stop = System.GC.GetTotalMemory(false); 12: timer.Stop(); 13: other = System.GC.GetTotalMemory(true); So let’s look at what happens when I run each of these blocks through the timer and memory check at 500,000 iterations: 1: Operator + - Time: 547, Memory: 56104540/55595960 - 500000 2: string.Format() - Time: 749, Memory: 57295812/55595960 - 500000 3: StringBuilder - Time: 608, Memory: 55312888/55595960 – 500000   Egad!  string.Format brings up the rear and + triumphs, well, at least in terms of speed.  The concat burns more memory than StringBuilder but less than string.Format().  This shows two main things: StringBuilder is not always the panacea many think it is. The difference between any of the three is miniscule! The second point is extremely important!  You will often here people who will grasp at results and say, “look, operator + is 10% faster than StringBuilder so always use StringBuilder.”  Statements like this are a disservice and often misleading.  For example, if I had a good guess at what the size of the string would be, I could have preallocated my StringBuffer like so:   1: for (int i = 0; i < num; i++) 2: { 3: // pre-declare StringBuilder to have 100 char buffer. 4: var builder = new StringBuilder(100); 5: builder.Append("This is test #"); 6: builder.Append(i); 7: builder.Append(" with a result of "); 8: builder.Append(strings[i]); 9: results[i] = builder.ToString(); 10: }   Now let’s look at the times: 1: Operator + - Time: 551, Memory: 56104412/55595960 - 500000 2: string.Format() - Time: 753, Memory: 57296484/55595960 - 500000 3: StringBuilder - Time: 525, Memory: 59779156/55595960 - 500000   Whoa!  All of the sudden StringBuilder is back on top again!  But notice, it takes more memory now.  This makes perfect sense if you examine the IL behind the scenes.  Whenever you do a string concat (+) in your code, it examines the lengths of the arguments and creates a StringBuilder behind the scenes of the appropriate size for you. But even IF we know the approximate size of our StringBuilder, look how much less readable it is!  That’s why I feel you should always take into account both readability and performance.  After all, consider all these timings are over 500,000 iterations.   That’s at best  0.0004 ms difference per call which is neglidgable at best.  The key is to pick the best tool for the job.  What do I mean?  Consider these awesome words of wisdom: Concatenate (+) is best at concatenating.  StringBuilder is best when you need to building. Format is best at formatting. Totally Earth-shattering, right!  But if you consider it carefully, it actually has a lot of beauty in it’s simplicity.  Remember, there is no magic bullet.  If one of these always beat the others we’d only have one and not three choices. The fact is, the concattenation operator (+) has been optimized for speed and looks the cleanest for joining together a known set of strings in the simplest manner possible. StringBuilder, on the other hand, excels when you need to build a string of inderterminant length.  Use it in those times when you are looping till you hit a stop condition and building a result and it won’t steer you wrong. String.Format seems to be the looser from the stats, but consider which of these is more readable.  Yes, ignore the fact that you could do this with ToString() on a DateTime.  1: // build a date via concatenation 2: var date1 = (month < 10 ? string.Empty : "0") + month + '/' 3: + (day < 10 ? string.Empty : "0") + '/' + year; 4:  5: // build a date via string builder 6: var builder = new StringBuilder(10); 7: if (month < 10) builder.Append('0'); 8: builder.Append(month); 9: builder.Append('/'); 10: if (day < 10) builder.Append('0'); 11: builder.Append(day); 12: builder.Append('/'); 13: builder.Append(year); 14: var date2 = builder.ToString(); 15:  16: // build a date via string.Format 17: var date3 = string.Format("{0:00}/{1:00}/{2:0000}", month, day, year); 18:  So the strength in string.Format is that it makes constructing a formatted string easy to read.  Yes, it’s slower, but look at how much more elegant it is to do zero-padding and anything else string.Format does. So my lesson is, don’t look for the silver bullet!  Choose the best tool.  Micro-optimization almost always bites you in the end because you’re sacrificing readability for performance, which is almost exactly the wrong choice 90% of the time. I love the rules of optimization.  They’ve been stated before in many forms, but here’s how I always remember them: For Beginners: Do not optimize. For Experts: Do not optimize yet. It’s so true.  Most of the time on today’s modern hardware, a micro-second optimization at the sake of readability will net you nothing because it won’t be your bottleneck.  Code for readability, choose the best tool for the job which will usually be the most readable and maintainable as well.  Then, and only then, if you need that extra performance boost after profiling your code and exhausting all other options… then you can start to think about optimizing.

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  • .NET string replace russian to english

    - by Fabio Beoni
    I have a strange problem replacing chars in string... I read a .txt file containing russian text, and starting from a list of letters russian to english (ru=en), I loop the list and I WOULD like to replace russian characters with english characters. The problem is: I can see in the debug the right reading of the russian and the right reading of the english, but using myWord = myWord.Replace(ruChar, enChar), the string is not replaced. My txt file is a UTF-8 encoding.

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  • String to Integer Smalltalk

    - by Anton
    Pretty simple question I need to get an integer from the user and I only know how to get a string from them. So if there is a way to get an integer from the user or to convert the string to an integer please let me know.

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  • A simple question about string.replace in C#

    - by Taz
    For example I have code below string txt="I have strings like West, and West; and west, and Western." I would like to replace the word west or West with some other word. But I would like not to replace West in Western. Can I use regular expression in string.replace? I used inputText.Replace("(\\sWest.\\s)",temp); It dos not work.

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  • String generation with regex criteria

    - by menjaraz
    I wonder wether it is feasible to implement an optimal string generator Class meeting the following requirements: Generation criteria using regex Lexicographical order enumeration. Count propetry Indexed access I don't feel comfortable with regular expression: I cannot come up with a starting piece of code but I just think of a naive implementation using a TList as a base class and use a filter (Regex) against "brute force" generated string. Thank you.

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  • String comparison in Objective-C

    - by james.ingham
    Hey, I've currently got a webserver set up which I communicate over SOAP with my iPhone app. I am returning a string containing a GUID and when I attempt to compare this with another string I get some strange results: Why would this not fire? Surely the two strings are a match? Thanks

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  • new line in a multi-line string

    - by Zka
    Trying to override a tostring in one of my classes. return string.Format(@" name = {0} ID = {1} sec nr = {2} acc nr = {3}", string, int, int ,int); // types But the thing is, the result isn't aligned when printed out: name = test ID = 42 sec nr = 11 acc nr = 55 Trying to add \n just prints it out without formating. Guessing it has something to do with @"" which I'm using for multi-lining. Would like it to print out : name = test ID = 42 sec nr = 11 acc nr = 55

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  • PHP regular expression find and append to string

    - by Gary
    I'm trying to use regular expressions (preg_match and preg_replace) to do the following: Find a string like this: {%title=append me to the title%} Then extract out the title part and the append me to the title part. Which I can then use to perform a str_replace(), etc. Given that I'm terrible at regular expressions, my code is failing... preg_match('/\{\%title\=(\w+.)\%\}/', $string, $matches); What pattern do I need? :/

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  • Getting my string value from my form into my class( not another form)

    - by jovany
    Hello all, I have a question regarding the some data which is being transfered from one form to my class. It's not going quite the way i'd like to , so I figured maybe there is someone who could help me. This is my code in my class Public Class DrawableTextBox Inherits Drawable Dim i_testString As Integer Private s_InsertLabel As String Private drawFont As Font Public Sub New(ByVal fore_color As Color, ByVal fill_color As Color, Optional ByVal line_width As Integer = 0, Optional ByVal new_x1 As Integer = 0, Optional ByVal new_y1 As Integer = 0, Optional ByVal new_x2 As Integer = 1, Optional ByVal new_y2 As Integer = 1) MyBase.New(fore_color, fill_color, line_width) X1 = new_x1 Y1 = new_y1 X2 = new_x2 Y2 = new_y2 Trace.WriteLine(s_InsertLabel) End Sub Friend WriteOnly Property _textBox() As String Set(ByVal Value As String) s_InsertLabel = Value Trace.WriteLine(s_InsertLabel) End Set End Property ' Draw the object on this Graphics surface. Public Overrides Sub Draw(ByVal gr As System.Drawing.Graphics) ' Make a Rectangle representing this rectangle. Dim rect As Rectangle = GetBounds() ' Fill the rectangle as usual. Dim fill_brush As New SolidBrush(FillColor) gr.FillRectangle(fill_brush, rect) fill_brush.Dispose() ' See if we're selected. If IsSelected Then ' Draw the rectangle highlighted. Dim highlight_pen As New Pen(Color.Yellow, LineWidth) gr.DrawRectangle(highlight_pen, rect) highlight_pen.Dispose() ' Draw grab handles. Trace.WriteLine("drawing the lines for my textbox") DrawGrabHandle(gr, X1, Y1) DrawGrabHandle(gr, X1, Y2) DrawGrabHandle(gr, X2, Y2) DrawGrabHandle(gr, X2, Y1) Else 'TextBox() Dim fg_pen As New Pen(Color.Red, LineWidth) 'Dim fontSize As Single = 0.1 + ((Y2 - Y1) / 2) Dim fontSize As Single = 20 Try Dim drawFont As New Font("Arial", fontSize, FontStyle.Bold) Trace.WriteLine(s_InsertLabel) gr.DrawString(s_InsertLabel, drawFont, Brushes.Brown, X1, Y1) Catch ex As ArgumentException End Try gr.DrawRectangle(Pens.Azure, rect) ' gr.DrawRectangle(fg_pen, rect) fg_pen.Dispose() End If End Sub Public Function GetValueString(ByVal ValueType As String) Return ValueType End Function ' Return the object's bounding rectangle. Public Overrides Function GetBounds() As System.Drawing.Rectangle Return New Rectangle( _ Min(X1, X2), _ Min(Y1, Y2), _ Abs(100), _ Abs(30)) Trace.WriteLine("don't forget to make variables in GetBounds DrawableTextbox") End Function ' Return True if this point is on the object. Public Overrides Function IsAt(ByVal x As Integer, ByVal y As Integer) As Boolean Return (x >= Min(X1, X2)) AndAlso _ (x <= Max(X1, X2)) AndAlso _ (y >= Min(Y1, Y2)) AndAlso _ (y <= Max(Y1, Y2)) End Function ' Move the second point. Public Overrides Sub NewPoint(ByVal x As Integer, ByVal y As Integer) X2 = x Y2 = y End Sub ' Return True if the object is empty (e.g. a zero-length line). Public Overrides Function IsEmpty() As Boolean Return (X1 = X2) AndAlso (Y1 = Y2) End Function End Class I've got a form with a textbox( form1) in which the text is being inserted and passed through a buttonclick (al via properties). As you can see I've placed several traces and in the property of the class my trace works fine , however if I look in my Draw function it is already gone. And I get a blank trace. Does anyone know what's happening here. thanks in advance. (forgive me I'm new )

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  • Copy string - Python

    - by Francisco Aleixo
    Ok guys I imagine this is easy but I can't seem to find how to copy a string. Simply COPY to the system like CTRL+C on a text. Basically I want to copy a string so I can for example, lets say, paste(ctrl+v). Sorry for such a trivial question, haha.

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  • Prevent backslash from being parsed by javascript for a string

    - by user286269
    A Flash AS3 IRC application sends me a string like "f\reak" to my javascript. Irc allows the \ in usernames which poses a problem when its passed to javascript. "f\reak" become "feak" in javascript making the \r into a carriage return. Is there a way to read the absolute value of the string instead of parsing a carriage return? These don't methods didn't work str.valueOf() str.toString() str.charAt(position of the \ ) this just sees the carriage return as well and not a backslash

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  • Cleanest way to build an SQL string in Java

    - by Vidar
    I want to build an SQL string to do database manipulation (updates, deletes, inserts, selects, that sort of thing) - instead of the awful string concat method using millions of "+"'s and quotes which is unreadable at best - there must be a better way. I did think of using MessageFormat - but its supposed to be used for user messages, although I think it would do a reasonable job - but I guess there should be something more aligned to SQL type operations in the java sql libraries. Would Groovy be any good? Any help much appreciated.

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  • compare string to date on mysql

    - by Mercer
    hello, i have a table with a date, this date is a string i want to compare this string with a date in my request. SELECT FE_CLIENT.* FROM FE_CLIENT WHERE D_DATFINPUBLI < '2010/06/03' How can i cast my column date_deb to a date for compare ..?

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