文字列連結パフォーマンステスト

Sample.java

import java.util.*;
import java.lang.*;
import java.io.*;

public class Sample
{
	public static void main (String[] args) throws java.lang.Exception
	{
		exec("+/10times", new Runnable() {
			@Override
			public void run() {
				String s = new String();
				for (int i = 0; i < 10; i++) {
					s += "hoge";
				}
			}
		});
		
		exec("StringBuilder/10times", new Runnable() {
			@Override
			public void run() {
				StringBuilder sb = new StringBuilder();
				for (int i = 0; i < 10; i++) {
					sb.append("hoge");
				}
			}
		});
		
		exec("StringBuffer/10times", new Runnable() {
			@Override
			public void run() {
				StringBuffer sb = new StringBuffer();
				for (int i = 0; i < 10; i++) {
					sb.append("hoge");
				}
			}
		});
	}
	
	private static void exec(String name, Runnable r) {
		long s = System.currentTimeMillis();
		
		for (int i = 0; i < 1000000000; i++) {
			r.run();
		}
		
		long e = System.currentTimeMillis();
		System.out.println(s + "/" + e);
		System.out.println(name + " : " + (e - s));
	}
}

/*
MacBook Pro (Retina 15-inch, Mid 2015, i7 2.5GHz, 16GB RAM)

$ javac Sample.java
$ java Sample
            +/10times @ 1000000sets : 214
StringBuilder/10times @ 1000000sets : 115
 StringBuffer/10times @ 1000000sets : 144
            +/1000times @ 10000sets : 5226
StringBuilder/1000times @ 10000sets : 76
 StringBuffer/1000times @ 10000sets : 84
*/