java写入大量数据

package performanceproblem;
import java.io.*;

public class PerformanceProblem
{
{
    public static void main(String[] args) throws Exception
    {    
        StringBuffer sb = new StringBuffer();
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("./performace.txt"));
        long start = System.currentTimeMillis() ;
        for(int i = 0; i < 100; ++i)
        {
            for(int j = 0; j < 1024; ++j)
            {
                for(int k = 0; k < 1024; ++k)
                {
                    sb.append("a");
                }
                sb.append("\n");
            }
            bufferedWriter.write(sb.toString());  // 积累1M数据，才写一次
            sb = sb.delete(0, sb.length());
        }
        bufferedWriter.flush();
        bufferedWriter.close();
        long end = System.currentTimeMillis() ;
        System.out.println((end - start) + "ms elapsed.");
    }
}