public class ConcatTimer {
    public static void main(String[] args) {
        final int iterations = 1000000;
        long startTimeConcat = System.nanoTime();
        for (int i = 0; i < iterations; i++) {
            String myString = "a: " + Math.random() + ", b: " + Math.random() + ", c: " + Math.random();
        }
        long endTimeConcat = System.nanoTime();

        long startTimeSb = System.nanoTime();
        for (int i = 0; i < iterations; i++) {
            StringBuilder sb = new StringBuilder();
            sb.append("a: ").append(Math.random())
                    .append(", b: ").append(Math.random())
                    .append(", c: ").append(Math.random());
            String myString = sb.toString();
        }
        long endTimeSb = System.nanoTime();
        System.out.println("Concat:        " + ((endTimeConcat - startTimeConcat) / (double)iterations));
        System.out.println("StringBuilder: " + ((endTimeSb - startTimeSb) / (double)iterations));
    }
}