BuilderTest.java

import java.lang.StringBuilder;

class BuilderTest {
  public static void main(String args[]) {
    long start = System.currentTimeMillis();
    for (int i = 0; i < 100000; ++i) {
      StringBuilder b = new StringBuilder();
      b.append("1");
      b.append("2");
      b.append("3");
      b.append("4");
      b.append("5");
      b.append("6");
      b.append("7");
      b.append("8");
      b.append("9");
      String n = b.toString();
    }
    System.out.println("Finished in " + (System.currentTimeMillis() - start));
  }
}

StringTest.java

class StringTest {
  public static void main(String args[]) {
    long start = System.currentTimeMillis();
    for (int i = 0; i < 100000; ++i) {
      String n = "";
      n += "1";
      n += "2";
      n += "3";
      n += "4";
      n += "5";
      n += "6";
      n += "7";
      n += "8";
      n += "9";
    }
    System.out.println("Finished in " + (System.currentTimeMillis() - start));
  }
}