Difference between string and StringBuilder in C

Question

What is the difference between string and StringBuilder    Also  what would be some examples for understanding

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From the StringBuilder Class documentation:

The String object is immutable. Every time you use one of the methods in the System.String class, you create a new string object in memory, which requires a new allocation of space for that new object. In situations where you need to perform repeated modifications to a string, the overhead associated with creating a new String object can be costly. The System.Text.StringBuilder class can be used when you want to modify a string without creating a new object. For example, using the StringBuilder class can boost performance when concatenating many strings together in a loop.

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String vs  StringBuilder  String  Under System namespace  Immutable  readonly  instance  Performance degrades when continuous change of value occurs  Thread-safe    StringBuilder  mutable string   Under System Text namespace Mutable instance Shows better performance since new changes are made to an existing instance    For a descriptive article about this topic with a lot of examples using ObjectIDGenerator  follow this link  Related Stack  Overflow question  Mutability of string when string doesn t change in C

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A String is an immutable type  This means that whenever you start concatenating strings with each other you re creating new strings each time  If you do so many times you end up with a lot of heap overhead and the risk of running out of memory   A StringBuilder instance is used to be able to append strings to the same instance  creating a string when you call the ToString method on it   Due to the overhead of instantiating a StringBuilder object it s said by Microsoft that it s useful to use when you have more than 5-10 string concatenations   For sample code I suggest you take a look here    String Class StringBuilder Class Using the StringBuilder Class

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Also the complexity of concatenations of String is O N2   while for StringBuffer it is O N    So there might be performance problem where we use concatenations in loops as a lot of new objects are created each time

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A string instance is immutable  You cannot change it after it was created  Any operation that appears to change the string instead returns a new instance   string foo    Foo      returns a new string instance instead of changing the old one string bar   foo Replace  o    a    string baz   foo    bar      ditto here   Immutable objects have some nice properties  such as they can be used across threads without fearing synchronization problems or that you can simply hand out your private backing fields directly without fearing that someone changes objects they shouldn t be changing  see arrays or mutable lists  which often need to be copied before returning them if that s not desired   But when used carelessly they may create severe performance problems  as nearly anything     if you need an example from a language that prides itself on speed of execution then look at C s string manipulation functions    When you need a mutable string  such as one you re contructing piece-wise or where you change lots of things  then you ll need a StringBuilder which is a buffer of characters that can be changed  This has  for the most part  performance implications  If you want a mutable string and instead do it with a normal string instance  then you ll end up with creating and destroying lots of objects unnecessarily  whereas a StringBuilder instance itself will change  negating the need for many new objects   Simple example  The following will make many programmers cringe with pain   string s   string Empty  for  i   0  i  lt  1000  i        s    i ToString              You ll end up creating 2001 strings here  2000 of which are thrown away  The same example using StringBuilder   StringBuilder sb   new StringBuilder    for  i   0  i  lt  1000  i        sb Append i     sb Append           This should place much less stress on the memory allocator  -   It should be noted however  that the C  compiler is reasonably smart when it comes to strings  For example  the following line  string foo    abc     def     efg     hij     will be joined by the compiler  leaving only a single string at runtime  Similarly  lines such as  string foo   a   b   c   d   e   f    will be rewritten to  string foo   string Concat a  b  c  d  e  f     so you don t have to pay for five nonsensical concatenations which would be the na  ve way of handling that  This won t save you in loops as above  unless the compiler unrolls the loop but I think only the JIT may actually do so and better don t bet on that

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String is immutable  which means that when you create a string you can never change it  Rather it will create a new string to store the new value  and this can be inefficient if you need to change the value of a string variable a lot   StringBuilder can be used to simulate a mutable string  so it is good for when you need to change a string a lot

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You can use the Clone method if you want to iterate through strings along with the string builder    It returns an object so you can convert to a string using the ToString method

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Strings are immutable i e if you change their value  the old value will be discarded and a new value is created on the heap  whereas in string builder we can modify the existing value without the new value being created   So performance-wise String Builder is beneficial as we are needlessly not occupying more memory space

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Major difference   String is immutable  It means that you can t modify a string at all  the result of modification is a new string  This is not effective if you plan to append to a string   StringBuilder is mutable  It can be modified in any way and it doesn t require creation of a new instance  When the work is done  ToString   can be called to get the string   Strings can participate in interning  It means that strings with same contents may have same addresses  StringBuilder can t be interned   String is the only class that can have a reference literal

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A String  System String  is a type defined inside the  NET framework  The String class is not mutable  This means that every time you do an action to an System String instance  the  NET compiler create a new instance of the string  This operation is hidden to the developer   A System Text StringBuilder is class that represents a mutable string  This class provides some useful methods that make the user able to manage the String wrapped by the StringBuilder  Notice that all the manipulations are made on the same StringBuilder instance    Microsoft encourages the use of StringBuilder because it is more effective in terms of memory usage

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String  A String instance is immutable  that is  we cannot change it after it was created  If we perform any operation on a String it will return a new instance  creates a new instance in memory  instead of modifying the existing instance value   StringBuilder  StringBuilder is mutable  that is  if we perform any operation on StringBuilder it will update the existing instance value and it will not create new instance   Difference between String and StringBuilder

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A StringBuilder will help you when you need to build strings in multiple steps   Instead of doing this   String x       x     first    x     second    x     third      you do  StringBuilder sb   new StringBuilder      sb Append  first     sb Append  second     sb Append  third    String x   sb ToString      The final effect is the same  but the StringBuilder will use less memory and will run faster  Instead of creating a new string which is the concatenation of the two  it will create the chunks separately  and only at the end it will unite them

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System String is a mutable object  meaning it cannot be modified after it   s been created  Please refer to Difference between string and StringBuilder in C   for better understanding

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