Just one point, I have to prove my decision by reference articles or spec papers. Like according to Java Language Specification and so on, or accroding by Jh.Bloch and so on. In some cases there don't have any information what I need. And I do my own experiment like this.
Benchmark (randomWordLength) Mode Cnt Score Error Units
StringBenchmark.apacheCommonsStringJoin 10 avgt 10 69.927 ± 15.804 ns/op
StringBenchmark.apacheCommonsStringJoin 20 avgt 10 60.087 ± 1.178 ns/op
StringBenchmark.apacheCommonsStringJoin 50 avgt 10 161.179 ± 11.760 ns/op
StringBenchmark.primitiveConcatenation 10 avgt 10 24.203 ± 0.211 ns/op
StringBenchmark.primitiveConcatenation 20 avgt 10 25.040 ± 0.364 ns/op
StringBenchmark.primitiveConcatenation 50 avgt 10 38.281 ± 0.895 ns/op
StringBenchmark.stringBuilder 10 avgt 10 20.765 ± 0.271 ns/op
StringBenchmark.stringBuilder 20 avgt 10 22.045 ± 0.611 ns/op
StringBenchmark.stringBuilder 50 avgt 10 38.298 ± 1.023 ns/op
StringBenchmark.stringConcat 10 avgt 10 64.063 ± 0.343 ns/op
StringBenchmark.stringConcat 20 avgt 10 67.399 ± 0.763 ns/op
StringBenchmark.stringConcat 50 avgt 10 76.619 ± 2.591 ns/op
StringBenchmark.stringFormat 10 avgt 10 673.458 ± 26.151 ns/op
StringBenchmark.stringFormat 20 avgt 10 711.718 ± 50.907 ns/op
StringBenchmark.stringFormat 50 avgt 10 733.963 ± 29.483 ns/op
StringBenchmark.stringJoin 10 avgt 10 92.567 ± 1.582 ns/op
StringBenchmark.stringJoin 20 avgt 10 121.745 ± 5.397 ns/op
StringBenchmark.stringJoin 50 avgt 10 182.598 ± 1.253 ns/op
VM version: JDK 1.8.0_152, Java HotSpot(TM) 64-Bit Server VM, 25.152-b16
OS: Linux Ubuntu 19.10
CPU: Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz 8 cores
RAM: 16Gb
Dear Java Developers, please avoid using String.format() to concatenate a string when a performance is an important for you.