Using the insert method with the position parameter set to 0 would be the same as prepending (i.e. inserting at the beginning). C# example : varStringBuilder.Insert(0, “someThing”); Java example : varStringBuilder.insert(0, “someThing”); It works both for C# and Java
Warning: It defeats the purpose of StringBuilder, but it does what you asked. Better technique (although still not ideal): Reverse each string you want to insert. Append each string to a StringBuilder. Reverse the entire StringBuilder when you’re done. This will turn an O(n²) solution into O(n).
Others have pointed out the deleteCharAt method, but here’s another alternative approach: Alternatively, use the Joiner class from Guava 🙂 As of Java 8, StringJoiner is part of the standard JRE.
If you have to write code for Internet Explorer make sure you chose an implementation, which uses array joins. Concatenating strings with the + or += operator are extremely slow on IE. This is especially true for IE6. On modern browsers += is usually just as fast as array joins. When I have to do lots of string concatenations I usually … Read more
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).
StringBuffer is synchronized, StringBuilder is not.