Runtime.getRuntime().exec("javac myprogram.java");

Package javax.tools Description

Provides interfaces for tools which can be invoked from a program, for example, compilers.

These interfaces and classes are required as part of the Java™ Platform, Standard Edition (Java SE), but there is no requirement to provide any tools implementing them.
...

There is no requirement for a compiler at runtime.

N>Бенчмарк, как всегда, некорректен Не видел еще ни одного бенчмарка, который адепты C# написали бы корректно для Java или ее производных.

D:\>java1 -version
java version "1.5.0_08"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_08-b03)
Java HotSpot(TM) Client VM (build 1.5.0_08-b03, mixed mode)

D:\>java -version
java version "1.5.0_06"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_06-b05)
BEA JRockit(R) (build R26.4.0-63-63688-1.5.0_06-20060626-2259-win-ia32, )

D:\>java1 -X
    -Xmixed           mixed mode execution (default)
    -Xint             interpreted mode execution only
    -Xbootclasspath:<directories and zip/jar files separated by ;>
                      set search path for bootstrap classes and resources
    -Xbootclasspath/a:<directories and zip/jar files separated by ;>
                      append to end of bootstrap class path
    -Xbootclasspath/p:<directories and zip/jar files separated by ;>
                      prepend in front of bootstrap class path
    -Xnoclassgc       disable class garbage collection
    -Xincgc           enable incremental garbage collection
    -Xloggc:<file>    log GC status to a file with time stamps
    -Xbatch           disable background compilation
    -Xms<size>        set initial Java heap size
    -Xmx<size>        set maximum Java heap size
    -Xss<size>        set java thread stack size
    -Xprof            output cpu profiling data
    -Xfuture          enable strictest checks, anticipating future default
    -Xrs              reduce use of OS signals by Java/VM (see documentation)
    -Xcheck:jni       perform additional checks for JNI functions
    -Xshare:off       do not attempt to use shared class data
    -Xshare:auto      use shared class data if possible (default)
    -Xshare:on        require using shared class data, otherwise fail.

D:\>java -X
    -Xbootclasspath:<directories and zip/jar files separated by :>
              set search path for bootstrap classes and resources
    -Xbootclasspath/a:<directories and zip/jar files separated by :>
              append to end of bootstrap class path
    -Xbootclasspath/p:<directories and zip/jar files separated by :>
              prepend in front of bootstrap class path
    -Xgcprio:[throughput|pausetime|deterministic]
              sets prio for the gc-system
                  throughput    optimizes the gc-behavior to achieve optimal
                                throughput (initially starts off with
                                single-spaced parallel GC mode but may switch
                                to other GC modes dynamically during runtime)
                  pausetime     optimizes the gc-behavior to achieve minimal
                                pause times (initially starts off with
                                single-spaced concurrent GC mode but may switch
                                to other GC modes dynamically during runtime)
                  deterministic optimizes the gc-behavior to ensure extremely
                                short pause times and limit the total number of
                                those pauses within a prescribed window (this
                                feature requires a valid license)
    -Xgc:[singlecon|gencon|parallel]
              used to set a static garbage collector
              will override the -Xgcprio option
                  singlecon     use the single-spaced concurrent garbage
                                collector algorithm (default in client mode)
                  gencon        use the generational concurrent
                                garbage collector algorithm
                  parallel      use the single-spaced parallel
                                garbage collector algorithm
                                (default in server mode)
    -Xms<size>[g|G|m|M|k|K]
              sets the initial Java heap size (ms)
                  server mode:  the default value is 25% of the amount
                                of free physical memory in the system
                                up to 64 MB with a minimum of 8 MB (default)
                  client mode:  the default value is 25% of the amount
                                of free physical memory in the system
                                up to 16 MB with a minimum of 8 MB
    -Xmx<size>[g|G|m|M|k|K]
              sets the maximum Java heap size (mx)
                  server mode:  the default value is the smallest of 75% of
                                physical memory and 1536 MB (default)
                  client mode:  the default value is the smallest of 75% of
                                physical memory and 64 MB
    -Xns<size>[g|G|m|M|k|K]
              sets the initial Java nursery size for generational collectors
                  server mode:  the default value is 10 MB per (default)
                  client mode:  the default value is 2 MB
    -Xss<size>[g|G|m|M|k|K]
              set initial stack size
    -Xpausetarget=<optimal_pause_time>[ms|s]
              JRockit will optimize the pause time to the given target,
              uses -Xgcprio:pausetime
                  ms            pause time specified in milliseconds (default)
                  s             pause time specified in seconds
    -Xnoclassgc
              disable class garbage collection
    -Xgcpause
              print pause times caused by the garbage collector
    -Xgcreport
              write extensive memory report at end of run
    -Xdebug
              enables debugging support in the VM
    -Xrun<library>
              loads and runs a library
    -Xjvmpi:[<argument1>=<value1>[,<argumentN>=<valueN>]]
              enable/disable groups of jvmpi events when running jvmpi
                  entryexit     (default on)
                  allocs        (default on)
                  monitors      (default on)
    -Xmanagement
              enable the management server needed by the
              JRockit Console
    -Xnoopt
              do not optimize code
    -Xstrictfp
              always use strict floating point calculations
    -Xverify
              do full bytecode verification
    -Xnohup or -Xrs
              JRockit will not process CTRL_LOGOFF_EVENT or SIGHUP events
    -Xverbose[:memory|load|jni|cpuinfo|codegen|opt]
              enable verbose output
    -Xverboselog:<file>
              log verbose output to a file
    -Xverbosetimestamp
              adds a timestamp to the verbose printout

Simple do-while: 1352
Repeat until: 4006

АХ>Runtime.getRuntime().exec("javac myprogram.java");
АХ>

void test() {
}

void main() {
for (int i = 0;i < 100 * 1000;i++) test();
long start = System.nanoTime();
for (int i = 0;i < 100 * 1000;i++) test();
long elapsed = System.nanoTime() - start;
}

АХ>2) попробовал HotSpot с -Xcomp -Xbatch (-Xcomp оказывается работает, правда об этом в опциях ни слова ).

АХ>Это как это они быстрее value типов ? Примеры давай.

public class Test30 {
    public int i = 0;
    public synchronized void test() { i++; }

    public static void x(String[] args) {
        long start = System.nanoTime();
        Test30 t = new Test30();
        for (int i = 0; i < 1000 * 1000; i++) t.test();
        System.out.println("Elapsed: " + (double)(System.nanoTime() - start) / 1.0e6);
    }

    public static void main(String[] args) {
        x(args); x(args); x(args); x(args);
    }
}

Elapsed: 33.746606
Elapsed: 43.532647
Elapsed: 26.349442
Elapsed: 28.652816

Elapsed: 46.199678
Elapsed: 43.042022
Elapsed: 2.238267
Elapsed: 2.646585