String append timings for different Java append methods.

gistfile1.java

package timings;

import java.util.Random;

public class StringTimings {
  public static void main(String[] args){
  	stringComp();
	}

	private static void stringComp() {
		int reps = 20;
		String[] ar = new String[1];
		long start;
		int numMethods=4;
		long total[] = new long[numMethods];
		StringBuilder hsb = new StringBuilder("\t"); // header
		StringBuilder psb[] = new StringBuilder[numMethods]; // %
		StringBuilder tsb[] = new StringBuilder[numMethods]; // total
		Random r = new Random();

		for (int i=0;i<psb.length;i++){
			psb[i] = new StringBuilder("% dif\t");
			tsb[i] = new StringBuilder("avg time(ms)\t");
		}

		for (int n=10;n<=10000000;n*=10){
			hsb.append(n+"\t");
			for (int i=0;i<total.length;i++)
				total[i] = 0;

			for (int j=0;j<reps;j++){
				int k =0;
				start = System.currentTimeMillis();
				float f;

				start = System.currentTimeMillis();
				for (int i=0;i<n;i++){
					f = r.nextFloat();
					ar[0] = stringSpeed1(f,f,f,f,f,f);
				}
				total[k++] += System.currentTimeMillis() - start;

				start = System.currentTimeMillis();
				for (int i=0;i<n;i++){
					f = r.nextFloat();
					ar[0] = stringSpeed2(f,f,f,f,f,f);
				}
				total[k++] += System.currentTimeMillis() - start;

				start = System.currentTimeMillis();
				for (int i=0;i<n;i++){
					f = r.nextFloat();
					ar[0] = stringSpeed3(f,f,f,f,f,f);
				}
				total[k++] += System.currentTimeMillis() - start;

				// The following String.format is so much slower
				// comment out for longer runs
				start = System.currentTimeMillis();
				for (int i=0;i<n;i++){
					f = r.nextFloat();
					ar[0] = stringSpeed4(f,f,f,f,f,f);
				}
				total[k++] += System.currentTimeMillis() - start;
			}
			long min = total[1];
			for (int i=0;i<total.length;i++)
				min = Math.min(min,total[i]);

			for (int i=0;i<total.length;i++){
				double avgpdif = 100.0*(total[i]-min)/min;
				double avgtotal = (double)total[i]/reps;
				tsb[i].append(avgtotal+"\t");
				psb[i].append(avgpdif +"\t");
//				System.out.println("avg time(ms)="+avgtotal+ "   avg %dif="+avgpdif);
			}
		}
		System.out.println(hsb.toString());
		for (int i=0; i<psb.length;i++){
			System.out.println(psb[i].toString());
		}
		System.out.println(hsb.toString());
		for (int i=0; i<tsb.length;i++){
			System.out.println(tsb[i].toString());
		}
	}

	public static String stringSpeed1(float a, float b, float c, float x, float y, float z){
		StringBuilder sb = new StringBuilder(72).append("[").append(a).append(",").append(b).append(",").append(c).append("][").
				append(x).append(",").append(y).append(",").append(z).append("]");
		return sb.toString();
	}

	public static String stringSpeed2(float a, float b, float c, float x, float y, float z){
		StringBuilder sb = new StringBuilder().append("[").append(a).append(",").append(b).append(",").append(c).append("][").
				append(x).append(",").append(y).append(",").append(z).append("]");
		return sb.toString();
	}

	public static String stringSpeed3(float a, float b, float c, float x, float y, float z){
		return "["+a+","+b+","+c+"]["+x+","+y+","+z+"]";
	}

	public static String stringSpeed4(float a, float b, float c, float x, float y, float z){
		return String.format("[%f,%f,%f][%f,%f,%f]", a,b,c,x,y,z);
	}

}