public static MethodHandle getMH(Class<?> c) {
try {
return lookup.findStatic(C.class, "m_" + c.getSimpleName(), methodType(c, String.class));
} catch (NoSuchMethodException | IllegalAccessException e) {
throw new RuntimeException(e);
}
}
public static void main(String[] arg) throws Throwable {
MethodHandles.Lookup lookup = MethodHandles.lookup();
Class thisClass = lookup.lookupClass(); // (who am I?)
MethodType methodType;
MethodHandle methodHandle;
Employee employee = new Employee();
String name;
Field fieldName = null;
for (Field field : Employee.class.getDeclaredFields()) {
if (field.getName().equals("name")) {
fieldName = field;
fieldName.setAccessible(true);
break;
}
}
// Lookup invoke dynamic
methodType = MethodType.methodType(String.class);
methodHandle = lookup.findVirtual(Employee.class, "getName", methodType);
name = (String) methodHandle.invokeExact(new Employee());
System.out.println("invoke dynamic " + name);
// Lookup reflection
Method method = Employee.class.getMethod("getName", new Class<?>[] {});
name = (String) method.invoke(new Employee());
System.out.println("reflection " + name);
// Lookup Handle Field Direct
MethodHandle methodHandleFieldDirect = lookup.unreflectGetter(fieldName);
name = (String) methodHandleFieldDirect.invokeExact(new Employee());
System.out.println("method handle for field direct " + name);
long start = 0;
long end = 0;
long times = 10_000;
long regularTime;
long invokeDynamicTime;
long reflectionTime;
long count = 0;
long invokeDynamicTimeUsingField;
long fieldDirect;
// warm up
for (int index = 0; index < times; index++) {
employee.getName();
name = (String) methodHandle.invokeExact(employee);
name = (String) method.invoke(employee);
name = (String) methodHandleFieldDirect.invokeExact(employee);
}
// regular method call time
start = System.nanoTime();
for (int index = 0; index < times; index++) {
name = employee.getName();
count += name.hashCode();
}
count = 0;
end = System.nanoTime();
regularTime = end - start;
System.out.printf("regular method call time = %d\n", regularTime / times);
// invoke dynamic method call time
start = System.nanoTime();
for (int index = 0; index < times; index++) {
name = (String) methodHandle.invokeExact(employee);
count += name.hashCode();
}
count = 0;
end = System.nanoTime();
invokeDynamicTime = end - start;
System.out.printf("invoke dynamic method call time = %d\n", invokeDynamicTime / times);
// reflection method call time
start = System.nanoTime();
for (int index = 0; index < times; index++) {
name = (String) method.invoke(employee);
count += name.hashCode();
}
count = 0;
end = System.nanoTime();
reflectionTime = end - start;
System.out.printf("reflection method call time = %d\n", reflectionTime / times);
//
start = System.nanoTime();
for (int index = 0; index < times; index++) {
name = (String) methodHandleFieldDirect.invokeExact(employee);
count += name.hashCode();
}
count = 0;
end = System.nanoTime();
invokeDynamicTimeUsingField = end - start;
System.out.printf(
"field method invoke dynamic call time = %d\n", invokeDynamicTimeUsingField / times);
//
start = System.nanoTime();
for (int index = 0; index < times; index++) {
name = (String) fieldName.get(employee);
count += name.hashCode();
}
count = 0;
end = System.nanoTime();
fieldDirect = end - start;
System.out.printf("field method reflection call time = %d\n", fieldDirect / times);
}