我写了一个小基准测试，测试了java.lang.invoke.MethodHandle、java.lang.reflect.Method和直接调用方法的性能。
我看到MethodHandle.invoke()的性能几乎与直接调用相同。但是我的测试结果显示另一种情况：使用MethodHandle调用要比反射慢三倍左右。这是我的问题吗？可能是某些JIT优化的结果吗？
public class Main {
public static final int COUNT = 100000000;
static TestInstance test = new TestInstance();
static void testInvokeDynamic() throws NoSuchMethodException, IllegalAccessException {
int [] ar = new int[COUNT];
MethodHandles.Lookup lookup = MethodHandles.lookup();
MethodType mt = MethodType.methodType(int.class);
MethodHandle handle = lookup.findStatic(TestInstance.class, "publicStaticMethod", mt) ;
try {
long start = System.currentTimeMillis();
for (int i=0; i<COUNT; i++) {
ar[i] = (int)handle.invokeExact();
}
long stop = System.currentTimeMillis();
System.out.println(ar);
System.out.println("InvokeDynamic time: " + (stop - start));
} catch (Throwable throwable) {
throwable.printStackTrace();
}
}
static void testDirect() {
int [] ar = new int[COUNT];
try {
long start = System.currentTimeMillis();
for (int i=0; i<COUNT; i++) {
ar[i] = TestInstance.publicStaticMethod();
}
long stop = System.currentTimeMillis();
System.out.println(ar);
System.out.println("Direct call time: " + (stop - start));
} catch (Throwable throwable) {
throwable.printStackTrace();
}
}
static void testReflection() throws NoSuchMethodException {
int [] ar = new int[COUNT];
Method method = test.getClass().getMethod("publicStaticMethod");
try {
long start = System.currentTimeMillis();
for (int i=0; i<COUNT; i++) {
ar[i] = (int)method.invoke(test);
}
long stop = System.currentTimeMillis();
System.out.println(ar);
System.out.println("Reflection time: " + (stop - start));
} catch (Throwable throwable) {
throwable.printStackTrace();
}
}
static void testReflectionAccessible() throws NoSuchMethodException {
int [] ar = new int[COUNT];
Method method = test.getClass().getMethod("publicStaticMethod");
method.setAccessible(true);
try {
long start = System.currentTimeMillis();
for (int i=0; i<COUNT; i++) {
ar[i] = (int)method.invoke(test);
}
long stop = System.currentTimeMillis();
System.out.println(ar);
System.out.println("Reflection accessible time: " + (stop - start));
} catch (Throwable throwable) {
throwable.printStackTrace();
}
}
public static void main(String ... args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException, InterruptedException {
Thread.sleep(5000);
Main.testDirect();
Main.testInvokeDynamic();
Main.testReflection();
Main.testReflectionAccessible();
System.out.println("\n___\n");
System.gc();
System.gc();
Main.testDirect();
Main.testInvokeDynamic();
Main.testReflection();
Main.testReflectionAccessible();
}
}
环境：java版本号为"1.7.0_11"，Java(TM) SE Runtime Environment的版本为(1.7.0_11-b21)，Java HotSpot(TM) 64位服务器虚拟机的版本为(23.6-b04, 混合模式)。操作系统- Windows 7 64位。