Amount of a given character contained in a Stringbuilder

Question

I have a Stringbuilder with these values: 12********3*4*.

There is a simple way to return the amount of asterisks without having to do a go over my Stringbuilder?

I’m using C# with Net Framework 3.5

Answer 1

Using Linq you can get the amount of characters that are asterisked as follows:

StringBuilder builder = new StringBuilder("12**********3*4*");

// É necessário usar ToString() para evitar chamar métodos que alteram o conteúdo do
// StringBuilder durante o processo de contagem dos caracteres, pois caso contrário
// isso poderia ter efeitos colaterais inesperados.
int totalDeAsteristicos = builder.ToString().Count(x => x =='*');

Answer 2

A possible solution:

StringBuilder valor = new StringBuilder("12**********3*4*");
int total = valor.Length - valor.Replace("*", "").Length;

It is worth remembering that any method used will have to look for the character inside the string, similar to an iteration. Due to internal optimizations, some methods may be faster than others. The only way to verify this is by testing and comparing each of the methods. In general, the minimum complexity for this type of operation will be O(n), where n is the string size.