Difference between string and StringBuilder in C #

Question

What is the difference between string and StringBuilder ?

Also, what would be a few examples to understand?

Answer 1

A string instance is immutable. You cannot change it after creating it. Any operation that appears to change a string 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 good properties, for example, they can be used in streams without fear of problems with synchronization, or simply you can simply transfer your private support fields without fear that someone will change objects that they should not change (see arrays or mutable lists that often need to be copied before returning them if this is not desired). But if used carelessly, they can cause serious performance problems (just like almost anything - if you need an example from a language that prides itself on speed of execution, then look at the C string management functions).

If you need a mutable string, for example, which you produce piece by piece or where you change a lot of things, you will need StringBuilder , which is a character buffer that you can change. This, for the most part, affects performance. If you want a variable string and instead execute it with a regular string instance, then you will end up creating and destroying many objects unnecessarily, while the StringBuilder instance StringBuilder will change, which negates the need for many new objects.

A simple example: the following will cause many programmers to contract in pain:

 string s = string.Empty; for (i = 0; i < 1000; i++) { s += i.ToString() + " "; } 

As a result, you will create lines of 2001, 2000 of which will be thrown out. Same example using StringBuilder:

 StringBuilder sb = new StringBuilder(); for (i = 0; i < 1000; i++) { sb.Append(i); sb.Append(' '); } 

This should significantly reduce the load on the memory allocator :-)

It should be noted, however, that the C # compiler is smart enough when it comes to strings. For example, the following line

 string foo = "abc" + "def" + "efg" + "hij"; 

will be combined by the compiler, leaving only one line at runtime. Similarly, strings 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 meaningless concatenations that would be a naive way to handle it. This will not save you in loops, as indicated above (if the compiler does not unroll the loop, but I think that only JIT can do this and it is better not to do this).

Answer 2

Difference between String and StringBuilder?

String

The string is unchanged. Immutable means when we create a string object that we cannot change. Any operation, such as inserting, replacing, or adding, has occurred with a row change, will simply undo the old value and create a new instance in memory to save the new value.

Example:

 string str = "hi"; str += "hello"; // New string instance will be created, instead of changing the old one str += "hw ru"; // Again new string instance will be created, instead of changing the old one 

StringBuilder:

String builder is changed, this means that when we create a string builder object, we can perform any operation, such as inserting, replacing, or adding without creating a new instance for each time.

Example:

 StringBuilder sb = new StringBuilder(""); sb.Append("hi"); sb.Append("hello"); string str = sb.ToString(); 

Read more about the "Differences between String and StringBuilder" in a tabular format with an example here.

Answer 3

A string is immutable, which means that when you create a string, you can never change it. Rather, it will create a new string to hold the new value, and this can be inefficient if you need to change the value of the string variable drastically.

StringBuilder can be used to simulate a mutable string, so it is suitable for cases where you need to change the string drastically.

Answer 4

String vs. StringBuilder

• line

  • In the System Namespace
  • Immutable (read-only) instance

  • Performance degrades when a constant change in value occurs

  • Flow

• StringBuilder (mutable string)

  1. In the System.Text namespace
  2. Mutable instance
  3. Shows better performance as new changes are made to an existing instance

For a descriptive article on this subject with many examples of using ObjectIDGenerator , click here .

Related question: line mutability when a line does not change in C #

Answer 5

line

The String instance is immutable, that is, we cannot change it after it has been created. If we perform any operation on a string, it will return a new instance (create a new instance in memory) instead of changing the existing value of the instance.

StringBuilder

StringBuilder is mutable, that is, if we perform any operation with StringBuilder, it will update the existing instance value and will not create a new instance.

Difference between String and StringBuilder

Answer 6

StringBuilder helps you when you need to build strings in several steps.

Instead of 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 StringBuilder will use less memory and will work faster. Instead of creating a new line, which is the union of the two, it will create portions separately, and only at the end will combine them.

Answer 7

From the StringBuilder class documentation :

The String object is immutable. Each time you use one of the methods in the System.String class, you create a new string object in memory that requires a new allocation of space for this new object. In situations where you need to make repeated modifications to a string, the overhead associated with creating a new String object can be expensive. The System.Text.StringBuilder class can be used when you want to change a row without creating a new object. For example, using the StringBuilder class can improve performance when combining many strings in a loop.

Answer 8

The main difference:

The string is unchanged. This means that you cannot change the line at all; The result of the modification is a new line. This is not effective if you plan to add to the row.

StringBuilder is mutable. It can be modified in any way and does not require the creation of a new instance. When the job is complete, ToString () can be called to get the string.

Strings can participate in internment. This means that lines with the same content can have the same address. StringBuilder cannot be interned.

String is the only class that can have a reference literal.

Answer 9

Strings are immutable, i.e. If you change their value, the old value will be discarded and a new value will be created on the heap, while in the row builder we can change the existing value without creating a new value.

Thus, String Builder is useful in terms of performance because we do not need to take up more space in memory.

Answer 10

A string is an immutable type. This means that whenever you start combining strings with each other, you create new strings every time. If you do this many times, you will have a lot of heaps and the risk of running out of memory.

A StringBuilder instance is used to be able to add strings to the same instance, creating a string when the ToString method is called for it.

Due to the overhead of creating an instance of the StringBuilder object, Microsoft has stated that it is useful to use it when you have more than 5-10 string concatenations.

For sample code, I suggest you look here:

• String class
• Class StringBuilder
• Using the StringBuilder Class

Answer 11

String (System.String) is a type defined inside the .NET platform. The String class is not mutable. This means that every time you perform an action on an instance of System.String, the .NET compiler creates a new instance of the string. This operation is hidden to the developer.

System.Text.StringBuilder is a class that represents a mutable string. This class provides several useful methods that allow the user to control the string wrapped by StringBuilder. Please note that all manipulations are performed in one instance of StringBuilder.

Microsoft encourages the use of StringBuilder because it is more efficient in terms of memory usage.

Answer 12

Also, String concatenation complexity is O (N2), while for StringBuffer it is O (N).

Therefore, a performance problem may arise when we use concatenation in loops, as many new objects are created each time.

Answer 13

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

Answer 14

System.String is a mutable object, that is, it cannot be modified after its creation. Please refer to the difference between string and StringBuilder in C #? for better understanding.