Difference between StringBuilder and StringBuffer

Question

What is the main difference between StringBuffer and StringBuilder? Is there any performance issues when deciding on any one of these?

Answer 1

StringBuilder is not thread safe. String Buffer is. More info here.

EDIT: As for performance , after hotspot kicks in , StringBuilder is the winner. However , for small iterations , the performance difference is negligible.

Answer 2

The major difference is StringBuffer is syncronized but StringBuilder is not.If you need to use more than one thread , then StringBuffer is recommended.But, as per the execution speed StringBuilder is faster than StringBuffer , because its not syncronized .

Answer 3

Pretty Good Question

Here are the differences, i have noticed :

StringBuffer :-

StringBuffer is  synchronized
StringBuffer is  thread-safe
StringBuffer is  slow (try to write a sample program and execute it, it will take more time than StringBuilder)

StringBuilder:-

 StringBuilder is not synchronized 
 StringBuilder is not thread-safe
 StringBuilder performance is better than StringBuffer.

Common thing :-

Both have same methods with same signatures. Both are mutable.

Answer 4

StringBuilder is faster than StringBuffer because it's not synchronized.

Here's a simple benchmark test:

public class Main {
    public static void main(String[] args) {
        int N = 77777777;
        long t;

        {
            StringBuffer sb = new StringBuffer();
            t = System.currentTimeMillis();
            for (int i = N; i --> 0 ;) {
                sb.append("");
            }
            System.out.println(System.currentTimeMillis() - t);
        }

        {
            StringBuilder sb = new StringBuilder();
            t = System.currentTimeMillis();
            for (int i = N; i > 0 ; i--) {
                sb.append("");
            }
            System.out.println(System.currentTimeMillis() - t);
        }
    }
}

A test run gives the numbers of 2241 ms for StringBuffer vs 753 ms for StringBuilder.

Answer 5

StringBuilder and StringBuffer are almost the same. The difference is that StringBuffer is synchronized and StringBuilder is not. Although, StringBuilder is faster than StringBuffer, the difference in performance is very little. StringBuilder is a SUN's replacement of StringBuffer. It just avoids synchronization from all the public methods. Rather than that, their functionality is the same.

Example of good usage:

If your text is going to change and is used by multiple threads, then it is better to use StringBuffer. If your text is going to change but is used by a single thread, then use StringBuilder.

Answer 6

Every method present in StringBuffer is Synchronized. hence at a time only one thread is allowed to operate StringBuffer object. It Increases waiting time of a Thread and Creates Performance problems to overcome this problem SUN People intoduced StringBuilder in 1.5 version.