When to use String and when StringBuilder in real applications? using example

If you want to change a string multiple times, then StringBuilder is a better option from performance point of view because it will not require new memory every time.
 

the String class and the StringBuilder class are both used for working with text. However, they have different characteristics and are suitable for different scenarios.

String class: The String class represents an immutable sequence of characters. Once a string is created, its value cannot be modified. Whenever you perform operations that modify a string, such as concatenation or replacing characters, a new string object is created.

Use String when:

• The string is relatively small and won't undergo frequent modifications.
• You need to concatenate a few strings or perform simple string manipulations.

Example:

string firstName = "John";
string lastName = "Doe";

string fullName = firstName + " " + lastName;
Console.WriteLine(fullName);  // Output: John Doe

In this example, the String class is used to concatenate the firstName and lastName strings to create a full name.

StringBuilder class: The StringBuilder class provides a mutable string object that can be modified without creating new instances. It is designed to efficiently handle scenarios where frequent modifications to a string are required, such as appending, inserting, or replacing characters.

Use StringBuilder when:

• You need to perform extensive string manipulations, such as concatenating large amounts of text or appending text in a loop.
• The string is expected to undergo frequent modifications, avoiding the creation of multiple intermediate string objects.

Example:

StringBuilder message = new StringBuilder("Hello");

for (int i = 0; i < 1000; i++)
{
    message.Append(" world");
}

Console.WriteLine(message.ToString());  // Output: Hello world world world ... (repeated 1000 times)

In this example, the StringBuilder class is used to efficiently append the string " world" to the message object in a loop, resulting in a long string without creating unnecessary intermediate string objects.

In summary, use the String class when you have a small string or need to perform simple string manipulations. On the other hand, use the StringBuilder class when you expect frequent modifications or need to concatenate or modify larger amounts of text efficiently, especially in loops or scenarios where performance is a concern.