benchmarks: simplify timestamp

import java.io.File;

import java.io.FileWriter;

import java.io.IOException;

import java.text.SimpleDateFormat;

import java.util.Date;

import java.util.LinkedList;

import java.util.List;

    public static final String baseDir;

    static {

        if (new File("benchmark_result/").isDirectory())

            baseDir = "benchmark_result_" + new Date().toString().replace(':', '.') + "/";

            baseDir = "benchmark_result_" + new SimpleDateFormat("yyyy-MM-dd_HH.mm.ss").format(new Date()) + "/";

        else baseDir = "benchmark_result/";

    }

    public static final String outputTimeFolder = baseDir + "Times/";