StringBuffer vs StringBuilder : Performance improvement figures

IN previous post StringBuffer vs StringBuilder, I have explained benefits of using StringBuilder over StringBuffer. Here are some performance figure using both for concatenating string.

package com.test;

public class StringConcatenateTest {

    public static void main(String[] args) {

        System.out.println("Using StringBuffer");

        long bufferTime = usingStringBuffer();

        System.out.println("Using String Builder");

        long builderTime = usingStringBuilder();

        double perc = ((double)(bufferTime-builderTime)/bufferTime)* 100;

        System.out.println("Improved in performance = " + perc + "%");

    }

    public static long usingStringBuffer(){

        long startTime = System.currentTimeMillis();

        System.out.println("\tStart time = "+ startTime);

        StringBuffer sb = new StringBuffer();

        for(int i=0;i<1000000;i++){

            sb.append("\tSample test string :: ");

        }

        String resultStr = sb.toString();

        long endTime = System.currentTimeMillis();

        System.out.println("\tEnd time ="+endTime);

        System.out.println("\tTotal time taken = "+ ((endTime - startTime)));

        return endTime-startTime;

    }

    public static long usingStringBuilder(){

        long startTime = System.currentTimeMillis();

        System.out.println("\tStart time = "+ startTime);

        StringBuilder sb = new StringBuilder();

        for(int i=0;i<1000000;i++){

            sb.append("\tSample test string :: ");

        }

        String resultStr = sb.toString();

        long endTime = System.currentTimeMillis();

        System.out.println("\tEnd time ="+endTime);

        System.out.println("\tTotal time taken = "+ ((endTime - startTime)));

        return endTime-startTime;

    }

  }

Here is the output

Using StringBuffer
    Start time = 1321171861338
    End time =1321171861909
    Total time taken = 571
Using String Builder
    Start time = 1321171861910
    End time =1321171862393
    Total time taken = 483
Improved in performance = 15.411558669001751%