I’ve got an article on this very topic. In summary (copied from the bottom of the page): Definitely use StringBuilder when you’re concatenating in a non-trivial loop – especially if you don’t know for sure (at compile time) how many iterations you’ll make through the loop. For example, reading a file a character at a … Read more
String is used to manipulate character strings that cannot be changed (read-only and immutable). StringBuffer is used to represent characters that can be modified. Performance wise, StringBuffer is faster when performing concatenations. This is because when you concatenate a String, you are creating a new object (internally) every time since String is immutable. You can … Read more
NOTE: This answer was written when .NET 2.0 was the current version. This may no longer apply to later versions. String.Format uses a StringBuilder internally: public static string Format(IFormatProvider provider, string format, params object[] args) { if ((format == null) || (args == null)) { throw new ArgumentNullException((format == null) ? “format” : “args”); } … Read more
I think the use of StringBuilder vs + really depends on the context you are using it in. Generally using JDK 1.6 and above the compiler will automatically join strings together using StringBuilder. String one = “abc”; String two = “xyz”; String three = one + two; This will compile String three as: String three … Read more
Two ways that work: Use stringBuilderObj.setLength(0). Allocate a new one with new StringBuilder() instead of clearing the buffer. Note that for performance-critical code paths, this approach can be significantly slower than the setLength-based approach (since a new object with a new buffer needs to be allocated, the old object becomes eligible for GC etc).
In .NET 2.0 it uses the String class internally. String is only immutable outside of the System namespace, so StringBuilder can do that. In .NET 4.0 String was changed to use char[]. In 2.0 StringBuilder looked like this public sealed class StringBuilder : ISerializable { // Fields private const string CapacityField = “Capacity”; internal const … Read more
I warmly suggest you to read The Sad Tragedy of Micro-Optimization Theater, by Jeff Atwood. It treats Simple Concatenation vs. StringBuilder vs. other methods. Now, if you want to see some numbers and graphs, follow the link 😉
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 … Read more
Short answer: it depends. Long answer: if you already have an array of strings to concatenate together (with a delimiter), String.Join is the fastest way of doing it. String.Join can look through all of the strings to work out the exact length it needs, then go again and copy all the data. This means there … Read more
String does not allow appending. Each method you invoke on a String creates a new object and returns it. This is because String is immutable – it cannot change its internal state. On the other hand StringBuilder is mutable. When you call append(..) it alters the internal char array, rather than creating a new string … Read more