JMH example for string manipulations

ReplacementsBenchmark.java

package io.github.pyvesb.jmh;

import java.util.concurrent.TimeUnit;
import java.util.regex.Pattern;

import org.apache.commons.lang3.RandomStringUtils;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.Warmup;
import org.openjdk.jmh.infra.Blackhole;

@Fork(value = 2, jvmArgsAppend = "-Djmh.stack.lines=3")
@Warmup(iterations = 20)
@Measurement(iterations = 20)
@State(Scope.Benchmark)
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
public class ReplacementsBenchmark {
	
	private static final Pattern PATTERN = Pattern.compile("\\s");

	private String value;

	@Setup
	public void setup() {
		value = RandomStringUtils.random(32, " abcdefghijklmnopqrstuvwxyz1234567890 ");
	}

	@Benchmark
	public void replaceAll(Blackhole blackhole) {
		blackhole.consume(value.replaceAll("\\s", "_"));
	}
	@Benchmark
	public void replaceAll_precompiled_pattern(Blackhole blackhole) {
		blackhole.consume(PATTERN.matcher(value).replaceAll("_"));
	}

	@Benchmark
	public void replace_strings(Blackhole blackhole) {
		blackhole.consume(value.replace(" ", "_"));
	}
	
	@Benchmark
	public void replace_chars(Blackhole blackhole) {
		blackhole.consume(value.replace(' ', '_'));
	}
}