String vs StringBuilder

gistfile1.txt

public class StringVsStringBuilder {
  public static void main(String[] args) {
		long start = System.nanoTime();
		String a = "";
		for(int i = 0; i < 10000; i++){
			a += "a";
		}
		System.out.println("Time for a String to build: " + (System.nanoTime() - start) + "ns");
		
		start = System.nanoTime();
		StringBuilder b = new StringBuilder();
		for(int i = 0; i < 10000; i++){
			b.append("a");
		}
		System.out.println("Time for a StringBuilder to build: " + (System.nanoTime() - start) + "ns");
	}

}