JavaSpeedTest

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class StringBuilderTest {

    public static final void main(String[] args) throws Exception {
        String str = "abcdefgh"+"efghefgh";
        int imax = 1024 / str.length() * 1024 * 4;

        long time = System.currentTimeMillis();
        System.out.println("exec.tm.sec\tstr.length\tallocated memory:free memory:memory used");
        Runtime runtime = Runtime.getRuntime();
        System.out.println("0\t\t0\t\t"+runtime.totalMemory()/1024 +":"+ runtime.freeMemory()/1024+":"+(runtime.totalMemory()-runtime.freeMemory())/1024);

        StringBuilder gstrBuilder = new StringBuilder("");
        int i=0;
        int lngth;

        Pattern p = Pattern.compile("efgh");
        Matcher m;
        while (i++ < imax+1000) {
            gstrBuilder.append(str);
            m = p.matcher(gstrBuilder);
            gstrBuilder = new StringBuilder(m.replaceAll("____"));
            lngth=str.length()*i;
            if ((lngth % (1024*256)) == 0) {
                System.out.println(((System.currentTimeMillis()-time)/1000)+"sec\t\t"+lngth/1024+"kb\t\t"+runtime.totalMemory()/1024+":"+runtime.freeMemory()/1024+":"+(runtime.totalMemory()-runtime.freeMemory())/1024);
            }
        }
    }
}