Absolutely not; here’s a simple example lifted from 4.0 via reflector: [SecuritySafeCritical] public StringBuilder Append(char value) { if (this.m_ChunkLength < this.m_ChunkChars.Length) { this.m_ChunkChars[this.m_ChunkLength++] = value; } else { this.Append(value, 1); } return this; } The attribute just handles callers, not thread-safety; this is absolutely not thread-safe. Update: looking at the source he references, this is … Read more
There is memory but no contiguous segment that can handle the size of your string builder. You have to know that each time the buffer of the string builder is too short, its size is doubled. If you can define (in the ctor) the size of your builder, it’s better. You MAY call GC.Collect() when … Read more
Problem I am afraid the test you have written is incorrect. The main requirement is to share the same StringBuilder instance between different threads. Whereas you are creating a StringBuilder object for each thread. The problem is that a new Threadsafe() initialises a new StringBuilder(): class Threadsafe { … StringBuilder sb = new StringBuilder(str); … … Read more
You can use the String javax.xml.bind.DatatypeConverter.printHexBinary(byte[]). e.g.: public static void main(String[] args) { byte[] array = new byte[] { 127, 15, 0 }; String hex = DatatypeConverter.printHexBinary(array); System.out.println(hex); // prints “7F0F00” }
When you use the + operator to build up a string: string s = “01”; s += “02”; s += “03”; s += “04”; then on the first concatenation we make a new string of length four and copy “01” and “02” into it — four characters are copied. On the second concatenation we make … Read more
The aim of using StringBuilder, i.e reducing memory. Is it achieved? No, not at all. That code is not using StringBuilder correctly. (I think you’ve misquoted it, though; surely there aren’t quotes around id2 and table?) Note that the aim (usually) is to reduce memory churn rather than total memory used, to make life a … Read more
Others have pointed out the deleteCharAt method, but here’s another alternative approach: String prefix = “”; for (String serverId : serverIds) { sb.append(prefix); prefix = “,”; sb.append(serverId); } Alternatively, use the Joiner class from Guava 🙂 As of Java 8, StringJoiner is part of the standard JRE.
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
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).