StringBuilderBench for https://stackoverflow.com/a/29013248/3614835

StringBuilderBench.java

package com.jeffreybosboom.stringbuilderbench;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.State;

@State(Scope.Thread)
public class StringBuilderBench {
	//promote to non-final fields to inhibit constant folding (see JMHSample_10_ConstantFold.java)
	private String really = "really ", long_string = "long string.", re = "re", al = "al", ly = "ly ";
    @Benchmark
    public String implicit() {
        String s = "";
		for (int i = 0; i < 10000; i++)
			s += really;
		s += long_string;
		return s;
    }
	@Benchmark
	public String explicit() {
		String s = "";
		for (int i = 0; i < 10000; i++)
			s = new StringBuilder().append(s).append(really).toString();
		s = new StringBuilder().append(s).append(long_string).toString();
		return s;
	}
	@Benchmark
    public String concat() {
        String s = "";
		for (int i = 0; i < 10000; i++)
			s = s.concat(really);
		s = s.concat(long_string);
		return s;
    }
	@Benchmark
	public String implicit3() {
        String s = "";
		for (int i = 0; i < 10000; i++) {
			s += re;
			s += al;
			s += ly;
		}
		s += long_string;
		return s;
	}
	@Benchmark
	public String explicit3() {
		String s = "";
		for (int i = 0; i < 10000; i++) {
			s = new StringBuilder().append(s).append(re).toString();
			s = new StringBuilder().append(s).append(al).toString();
			s = new StringBuilder().append(s).append(ly).toString();
		}
		s = new StringBuilder().append(s).append(long_string).toString();
		return s;
	}
	@Benchmark
	public String concat3() {
        String s = "";
		for (int i = 0; i < 10000; i++) {
			s = s.concat(re);
			s = s.concat(al);
			s = s.concat(ly);
		}
		s = s.concat(long_string);
		return s;
	}
	@Benchmark
	public String smart() {
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < 10000; i++)
			sb.append(really);
		sb.append(long_string);
		return sb.toString();
	}
	@Benchmark
	public String smart3() {
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < 10000; i++) {
			sb.append(re);
			sb.append(al);
			sb.append(ly);
		}
		sb.append(long_string);
		return sb.toString();
	}
}

StringBuilderBench.log

# JMH 1.6.2 (released 7 days ago)
# VM invoker: /data/scratch/jbosboom/jdk1.8.0_40/jre/bin/java
# VM options: <none>
# Warmup: 10 iterations, 5 s each
# Measurement: 30 iterations, 5 s each
# Timeout: 10 min per iteration
# Threads: 1 thread, will synchronize iterations
# Benchmark mode: Throughput, ops/time
# Benchmark: com.jeffreybosboom.stringbuilderbench.StringBuilderBench.concat

# Run progress: 0.00% complete, ETA 00:26:40
# Fork: 1 of 1
# Warmup Iteration   1: 6.777 ops/s
# Warmup Iteration   2: 6.891 ops/s
# Warmup Iteration   3: 9.250 ops/s
# Warmup Iteration   4: 9.545 ops/s
# Warmup Iteration   5: 10.187 ops/s
# Warmup Iteration   6: 10.078 ops/s
# Warmup Iteration   7: 10.719 ops/s
# Warmup Iteration   8: 10.924 ops/s
# Warmup Iteration   9: 10.998 ops/s
# Warmup Iteration  10: 10.923 ops/s
Iteration   1: 10.087 ops/s
Iteration   2: 8.247 ops/s
Iteration   3: 7.528 ops/s
Iteration   4: 9.999 ops/s
Iteration   5: 10.762 ops/s
Iteration   6: 9.126 ops/s
Iteration   7: 9.458 ops/s
Iteration   8: 10.575 ops/s
Iteration   9: 11.012 ops/s
Iteration  10: 10.551 ops/s
Iteration  11: 10.067 ops/s
Iteration  12: 9.181 ops/s
Iteration  13: 8.410 ops/s
Iteration  14: 10.142 ops/s
Iteration  15: 10.819 ops/s
Iteration  16: 10.989 ops/s
Iteration  17: 10.923 ops/s
Iteration  18: 11.047 ops/s
Iteration  19: 8.234 ops/s
Iteration  20: 7.091 ops/s
Iteration  21: 7.082 ops/s
Iteration  22: 7.812 ops/s
Iteration  23: 10.822 ops/s
Iteration  24: 10.996 ops/s
Iteration  25: 11.007 ops/s
Iteration  26: 11.006 ops/s
Iteration  27: 8.973 ops/s
Iteration  28: 7.117 ops/s
Iteration  29: 10.632 ops/s
Iteration  30: 10.860 ops/s


Result: 9.685 ±(99.9%) 0.924 ops/s [Average]
  Statistics: (min, avg, max) = (7.082, 9.685, 11.047), stdev = 1.382
  Confidence interval (99.9%): [8.762, 10.609]


# JMH 1.6.2 (released 7 days ago)
# VM invoker: /data/scratch/jbosboom/jdk1.8.0_40/jre/bin/java
# VM options: <none>
# Warmup: 10 iterations, 5 s each
# Measurement: 30 iterations, 5 s each
# Timeout: 10 min per iteration
# Threads: 1 thread, will synchronize iterations
# Benchmark mode: Throughput, ops/time
# Benchmark: com.jeffreybosboom.stringbuilderbench.StringBuilderBench.concat3

# Run progress: 12.50% complete, ETA 00:23:39
# Fork: 1 of 1
# Warmup Iteration   1: 2.521 ops/s
# Warmup Iteration   2: 2.783 ops/s
# Warmup Iteration   3: 2.326 ops/s
# Warmup Iteration   4: 2.696 ops/s
# Warmup Iteration   5: 2.844 ops/s
# Warmup Iteration   6: 2.751 ops/s
# Warmup Iteration   7: 2.966 ops/s
# Warmup Iteration   8: 2.840 ops/s
# Warmup Iteration   9: 2.569 ops/s
# Warmup Iteration  10: 3.038 ops/s
Iteration   1: 2.876 ops/s
Iteration   2: 2.759 ops/s
Iteration   3: 3.216 ops/s
Iteration   4: 2.779 ops/s
Iteration   5: 2.770 ops/s
Iteration   6: 2.910 ops/s
Iteration   7: 2.732 ops/s
Iteration   8: 2.871 ops/s
Iteration   9: 2.905 ops/s
Iteration  10: 2.987 ops/s
Iteration  11: 2.679 ops/s
Iteration  12: 2.999 ops/s
Iteration  13: 2.995 ops/s
Iteration  14: 3.193 ops/s
Iteration  15: 3.227 ops/s
Iteration  16: 3.261 ops/s
Iteration  17: 3.382 ops/s
Iteration  18: 3.368 ops/s
Iteration  19: 3.441 ops/s
Iteration  20: 3.541 ops/s
Iteration  21: 3.599 ops/s
Iteration  22: 3.304 ops/s
Iteration  23: 3.627 ops/s
Iteration  24: 3.688 ops/s
Iteration  25: 3.703 ops/s
Iteration  26: 3.709 ops/s
Iteration  27: 2.812 ops/s
Iteration  28: 3.395 ops/s
Iteration  29: 3.704 ops/s
Iteration  30: 3.028 ops/s


Result: 3.182 ±(99.9%) 0.228 ops/s [Average]
  Statistics: (min, avg, max) = (2.679, 3.182, 3.709), stdev = 0.341
  Confidence interval (99.9%): [2.954, 3.410]


# JMH 1.6.2 (released 7 days ago)
# VM invoker: /data/scratch/jbosboom/jdk1.8.0_40/jre/bin/java
# VM options: <none>
# Warmup: 10 iterations, 5 s each
# Measurement: 30 iterations, 5 s each
# Timeout: 10 min per iteration
# Threads: 1 thread, will synchronize iterations
# Benchmark mode: Throughput, ops/time
# Benchmark: com.jeffreybosboom.stringbuilderbench.StringBuilderBench.explicit

# Run progress: 25.00% complete, ETA 00:20:26
# Fork: 1 of 1
# Warmup Iteration   1: 1.565 ops/s
# Warmup Iteration   2: 7.091 ops/s
# Warmup Iteration   3: 9.830 ops/s
# Warmup Iteration   4: 9.013 ops/s
# Warmup Iteration   5: 7.237 ops/s
# Warmup Iteration   6: 7.186 ops/s
# Warmup Iteration   7: 7.385 ops/s
# Warmup Iteration   8: 8.223 ops/s
# Warmup Iteration   9: 10.196 ops/s
# Warmup Iteration  10: 9.749 ops/s
Iteration   1: 9.911 ops/s
Iteration   2: 10.574 ops/s
Iteration   3: 10.835 ops/s
Iteration   4: 9.047 ops/s
Iteration   5: 10.138 ops/s
Iteration   6: 9.845 ops/s
Iteration   7: 10.792 ops/s
Iteration   8: 7.401 ops/s
Iteration   9: 7.199 ops/s
Iteration  10: 7.302 ops/s
Iteration  11: 7.484 ops/s
Iteration  12: 7.417 ops/s
Iteration  13: 9.803 ops/s
Iteration  14: 10.305 ops/s
Iteration  15: 10.298 ops/s
Iteration  16: 9.691 ops/s
Iteration  17: 10.377 ops/s
Iteration  18: 10.701 ops/s
Iteration  19: 7.581 ops/s
Iteration  20: 7.364 ops/s
Iteration  21: 7.437 ops/s
Iteration  22: 7.989 ops/s
Iteration  23: 7.520 ops/s
Iteration  24: 8.628 ops/s
Iteration  25: 7.974 ops/s
Iteration  26: 8.774 ops/s
Iteration  27: 10.551 ops/s
Iteration  28: 10.238 ops/s
Iteration  29: 9.481 ops/s
Iteration  30: 9.690 ops/s


Result: 9.078 ±(99.9%) 0.884 ops/s [Average]
  Statistics: (min, avg, max) = (7.199, 9.078, 10.835), stdev = 1.323
  Confidence interval (99.9%): [8.194, 9.962]


# JMH 1.6.2 (released 7 days ago)
# VM invoker: /data/scratch/jbosboom/jdk1.8.0_40/jre/bin/java
# VM options: <none>
# Warmup: 10 iterations, 5 s each
# Measurement: 30 iterations, 5 s each
# Timeout: 10 min per iteration
# Threads: 1 thread, will synchronize iterations
# Benchmark mode: Throughput, ops/time
# Benchmark: com.jeffreybosboom.stringbuilderbench.StringBuilderBench.explicit3

# Run progress: 37.50% complete, ETA 00:16:59
# Fork: 1 of 1
# Warmup Iteration   1: 0.511 ops/s
# Warmup Iteration   2: 0.444 ops/s
# Warmup Iteration   3: 0.488 ops/s
# Warmup Iteration   4: 1.584 ops/s
# Warmup Iteration   5: 9.570 ops/s
# Warmup Iteration   6: 10.081 ops/s
# Warmup Iteration   7: 7.962 ops/s
# Warmup Iteration   8: 7.509 ops/s
# Warmup Iteration   9: 7.103 ops/s
# Warmup Iteration  10: 9.523 ops/s
Iteration   1: 8.569 ops/s
Iteration   2: 8.554 ops/s
Iteration   3: 8.963 ops/s
Iteration   4: 8.357 ops/s
Iteration   5: 8.973 ops/s
Iteration   6: 8.390 ops/s
Iteration   7: 8.315 ops/s
Iteration   8: 8.463 ops/s
Iteration   9: 8.365 ops/s
Iteration  10: 8.607 ops/s
Iteration  11: 8.649 ops/s
Iteration  12: 8.450 ops/s
Iteration  13: 8.996 ops/s
Iteration  14: 8.041 ops/s
Iteration  15: 8.417 ops/s
Iteration  16: 9.429 ops/s
Iteration  17: 8.247 ops/s
Iteration  18: 8.268 ops/s
Iteration  19: 8.269 ops/s
Iteration  20: 8.805 ops/s
Iteration  21: 8.549 ops/s
Iteration  22: 8.700 ops/s
Iteration  23: 8.146 ops/s
Iteration  24: 8.286 ops/s
Iteration  25: 8.987 ops/s
Iteration  26: 8.728 ops/s
Iteration  27: 8.129 ops/s
Iteration  28: 8.980 ops/s
Iteration  29: 8.952 ops/s
Iteration  30: 9.327 ops/s


Result: 8.597 ±(99.9%) 0.237 ops/s [Average]
  Statistics: (min, avg, max) = (8.041, 8.597, 9.429), stdev = 0.354
  Confidence interval (99.9%): [8.360, 8.834]


# JMH 1.6.2 (released 7 days ago)
# VM invoker: /data/scratch/jbosboom/jdk1.8.0_40/jre/bin/java
# VM options: <none>
# Warmup: 10 iterations, 5 s each
# Measurement: 30 iterations, 5 s each
# Timeout: 10 min per iteration
# Threads: 1 thread, will synchronize iterations
# Benchmark mode: Throughput, ops/time
# Benchmark: com.jeffreybosboom.stringbuilderbench.StringBuilderBench.implicit

# Run progress: 50.00% complete, ETA 00:13:38
# Fork: 1 of 1
# Warmup Iteration   1: 1.534 ops/s
# Warmup Iteration   2: 6.136 ops/s
# Warmup Iteration   3: 10.235 ops/s
# Warmup Iteration   4: 10.273 ops/s
# Warmup Iteration   5: 10.676 ops/s
# Warmup Iteration   6: 10.948 ops/s
# Warmup Iteration   7: 8.115 ops/s
# Warmup Iteration   8: 10.813 ops/s
# Warmup Iteration   9: 7.350 ops/s
# Warmup Iteration  10: 9.554 ops/s
Iteration   1: 10.275 ops/s
Iteration   2: 10.795 ops/s
Iteration   3: 9.877 ops/s
Iteration   4: 11.061 ops/s
Iteration   5: 11.163 ops/s
Iteration   6: 11.125 ops/s
Iteration   7: 11.140 ops/s
Iteration   8: 11.100 ops/s
Iteration   9: 9.376 ops/s
Iteration  10: 11.165 ops/s
Iteration  11: 11.045 ops/s
Iteration  12: 11.119 ops/s
Iteration  13: 11.152 ops/s
Iteration  14: 8.873 ops/s
Iteration  15: 10.660 ops/s
Iteration  16: 7.297 ops/s
Iteration  17: 7.212 ops/s
Iteration  18: 9.367 ops/s
Iteration  19: 11.126 ops/s
Iteration  20: 11.140 ops/s
Iteration  21: 8.634 ops/s
Iteration  22: 7.160 ops/s
Iteration  23: 10.779 ops/s
Iteration  24: 11.227 ops/s
Iteration  25: 8.859 ops/s
Iteration  26: 11.212 ops/s
Iteration  27: 11.168 ops/s
Iteration  28: 11.258 ops/s
Iteration  29: 11.139 ops/s
Iteration  30: 11.209 ops/s


Result: 10.290 ±(99.9%) 0.878 ops/s [Average]
  Statistics: (min, avg, max) = (7.160, 10.290, 11.258), stdev = 1.315
  Confidence interval (99.9%): [9.412, 11.169]


# JMH 1.6.2 (released 7 days ago)
# VM invoker: /data/scratch/jbosboom/jdk1.8.0_40/jre/bin/java
# VM options: <none>
# Warmup: 10 iterations, 5 s each
# Measurement: 30 iterations, 5 s each
# Timeout: 10 min per iteration
# Threads: 1 thread, will synchronize iterations
# Benchmark mode: Throughput, ops/time
# Benchmark: com.jeffreybosboom.stringbuilderbench.StringBuilderBench.implicit3

# Run progress: 62.50% complete, ETA 00:10:12
# Fork: 1 of 1
# Warmup Iteration   1: 0.527 ops/s
# Warmup Iteration   2: 0.642 ops/s
# Warmup Iteration   3: 0.417 ops/s
# Warmup Iteration   4: 4.773 ops/s
# Warmup Iteration   5: 9.694 ops/s
# Warmup Iteration   6: 10.227 ops/s
# Warmup Iteration   7: 9.956 ops/s
# Warmup Iteration   8: 9.660 ops/s
# Warmup Iteration   9: 7.547 ops/s
# Warmup Iteration  10: 7.467 ops/s
Iteration   1: 9.436 ops/s
Iteration   2: 10.723 ops/s
Iteration   3: 8.949 ops/s
Iteration   4: 10.638 ops/s
Iteration   5: 10.904 ops/s
Iteration   6: 10.149 ops/s
Iteration   7: 7.930 ops/s
Iteration   8: 8.354 ops/s
Iteration   9: 11.007 ops/s
Iteration  10: 10.167 ops/s
Iteration  11: 11.039 ops/s
Iteration  12: 10.451 ops/s
Iteration  13: 10.574 ops/s
Iteration  14: 7.500 ops/s
Iteration  15: 7.394 ops/s
Iteration  16: 7.475 ops/s
Iteration  17: 7.572 ops/s
Iteration  18: 10.654 ops/s
Iteration  19: 8.949 ops/s
Iteration  20: 10.344 ops/s
Iteration  21: 8.347 ops/s
Iteration  22: 10.357 ops/s
Iteration  23: 7.527 ops/s
Iteration  24: 7.666 ops/s
Iteration  25: 8.393 ops/s
Iteration  26: 8.633 ops/s
Iteration  27: 9.802 ops/s
Iteration  28: 9.783 ops/s
Iteration  29: 8.993 ops/s
Iteration  30: 9.396 ops/s


Result: 9.303 ±(99.9%) 0.838 ops/s [Average]
  Statistics: (min, avg, max) = (7.394, 9.303, 11.039), stdev = 1.254
  Confidence interval (99.9%): [8.466, 10.141]


# JMH 1.6.2 (released 7 days ago)
# VM invoker: /data/scratch/jbosboom/jdk1.8.0_40/jre/bin/java
# VM options: <none>
# Warmup: 10 iterations, 5 s each
# Measurement: 30 iterations, 5 s each
# Timeout: 10 min per iteration
# Threads: 1 thread, will synchronize iterations
# Benchmark mode: Throughput, ops/time
# Benchmark: com.jeffreybosboom.stringbuilderbench.StringBuilderBench.smart

# Run progress: 75.00% complete, ETA 00:06:49
# Fork: 1 of 1
# Warmup Iteration   1: 5208.142 ops/s
# Warmup Iteration   2: 5582.418 ops/s
# Warmup Iteration   3: 6173.640 ops/s
# Warmup Iteration   4: 4740.203 ops/s
# Warmup Iteration   5: 5144.127 ops/s
# Warmup Iteration   6: 4916.250 ops/s
# Warmup Iteration   7: 5870.128 ops/s
# Warmup Iteration   8: 6027.848 ops/s
# Warmup Iteration   9: 5993.312 ops/s
# Warmup Iteration  10: 6024.028 ops/s
Iteration   1: 6031.430 ops/s
Iteration   2: 4871.233 ops/s
Iteration   3: 4817.737 ops/s
Iteration   4: 5097.049 ops/s
Iteration   5: 4862.744 ops/s
Iteration   6: 4926.390 ops/s
Iteration   7: 5779.711 ops/s
Iteration   8: 4998.130 ops/s
Iteration   9: 6004.556 ops/s
Iteration  10: 5543.246 ops/s
Iteration  11: 6049.319 ops/s
Iteration  12: 6072.734 ops/s
Iteration  13: 6252.073 ops/s
Iteration  14: 6240.111 ops/s
Iteration  15: 6241.159 ops/s
Iteration  16: 5063.071 ops/s
Iteration  17: 4834.826 ops/s
Iteration  18: 4853.578 ops/s
Iteration  19: 5475.422 ops/s
Iteration  20: 6081.708 ops/s
Iteration  21: 6278.642 ops/s
Iteration  22: 4904.057 ops/s
Iteration  23: 5600.939 ops/s
Iteration  24: 5042.859 ops/s
Iteration  25: 5292.616 ops/s
Iteration  26: 5059.796 ops/s
Iteration  27: 5235.415 ops/s
Iteration  28: 5491.625 ops/s
Iteration  29: 4993.133 ops/s
Iteration  30: 5164.959 ops/s


Result: 5438.676 ±(99.9%) 352.088 ops/s [Average]
  Statistics: (min, avg, max) = (4817.737, 5438.676, 6278.642), stdev = 526.989
  Confidence interval (99.9%): [5086.588, 5790.764]


# JMH 1.6.2 (released 7 days ago)
# VM invoker: /data/scratch/jbosboom/jdk1.8.0_40/jre/bin/java
# VM options: <none>
# Warmup: 10 iterations, 5 s each
# Measurement: 30 iterations, 5 s each
# Timeout: 10 min per iteration
# Threads: 1 thread, will synchronize iterations
# Benchmark mode: Throughput, ops/time
# Benchmark: com.jeffreybosboom.stringbuilderbench.StringBuilderBench.smart3

# Run progress: 87.50% complete, ETA 00:03:24
# Fork: 1 of 1
# Warmup Iteration   1: 2938.131 ops/s
# Warmup Iteration   2: 2875.106 ops/s
# Warmup Iteration   3: 3092.491 ops/s
# Warmup Iteration   4: 2824.023 ops/s
# Warmup Iteration   5: 3330.853 ops/s
# Warmup Iteration   6: 3314.156 ops/s
# Warmup Iteration   7: 3275.936 ops/s
# Warmup Iteration   8: 2911.280 ops/s
# Warmup Iteration   9: 3391.046 ops/s
# Warmup Iteration  10: 3424.604 ops/s
Iteration   1: 3411.904 ops/s
Iteration   2: 3426.183 ops/s
Iteration   3: 3423.284 ops/s
Iteration   4: 3436.536 ops/s
Iteration   5: 3443.747 ops/s
Iteration   6: 3049.587 ops/s
Iteration   7: 3413.533 ops/s
Iteration   8: 2913.896 ops/s
Iteration   9: 3348.923 ops/s
Iteration  10: 3408.199 ops/s
Iteration  11: 3418.061 ops/s
Iteration  12: 3373.853 ops/s
Iteration  13: 3426.152 ops/s
Iteration  14: 3423.919 ops/s
Iteration  15: 3408.160 ops/s
Iteration  16: 3414.307 ops/s
Iteration  17: 3393.305 ops/s
Iteration  18: 3396.163 ops/s
Iteration  19: 3416.338 ops/s
Iteration  20: 3418.330 ops/s
Iteration  21: 3410.160 ops/s
Iteration  22: 3421.332 ops/s
Iteration  23: 3412.688 ops/s
Iteration  24: 3417.404 ops/s
Iteration  25: 3375.491 ops/s
Iteration  26: 3409.398 ops/s
Iteration  27: 3406.259 ops/s
Iteration  28: 2929.081 ops/s
Iteration  29: 2944.708 ops/s
Iteration  30: 2959.131 ops/s


Result: 3335.001 ±(99.9%) 115.600 ops/s [Average]
  Statistics: (min, avg, max) = (2913.896, 3335.001, 3443.747), stdev = 173.025
  Confidence interval (99.9%): [3219.401, 3450.601]


# Run complete. Total time: 00:27:08

Benchmark                      Mode  Cnt     Score     Error  Units
StringBuilderBench.concat     thrpt   30     9.685 ±   0.924  ops/s
StringBuilderBench.concat3    thrpt   30     3.182 ±   0.228  ops/s
StringBuilderBench.explicit   thrpt   30     9.078 ±   0.884  ops/s
StringBuilderBench.explicit3  thrpt   30     8.597 ±   0.237  ops/s
StringBuilderBench.implicit   thrpt   30    10.290 ±   0.878  ops/s
StringBuilderBench.implicit3  thrpt   30     9.303 ±   0.838  ops/s
StringBuilderBench.smart      thrpt   30  5438.676 ± 352.088  ops/s
StringBuilderBench.smart3     thrpt   30  3335.001 ± 115.600  ops/s