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);
}
static {
Field charsField =
AccessController.doPrivileged(
new PrivilegedAction<Field>() {
@Override
public Field run() {
Field charsField;
try {
charsField = String.class.getDeclaredField("value");
charsField.setAccessible(true);
} catch (NoSuchFieldException ex) {
LOG.info("char array stealing from String not supported", ex);
charsField = null;
} catch (SecurityException ex) {
throw new RuntimeException(ex);
}
return charsField;
}
});
MethodHandles.Lookup lookup = MethodHandles.lookup();
if (charsField != null) {
try {
CHARS_FIELD_GET = lookup.unreflectGetter(charsField);
} catch (IllegalAccessException ex) {
throw new ExceptionInInitializerError(ex);
}
} else {
CHARS_FIELD_GET = null;
}
// up until u45 String(int offset, int count, char value[]) {
// u45 reverted to: String(char[] value, boolean share) {
Constructor<String> prConstr =
AccessController.doPrivileged(
new PrivilegedAction<Constructor<String>>() {
@Override
public Constructor<String> run() {
Constructor<String> constr;
try {
constr = String.class.getDeclaredConstructor(char[].class, boolean.class);
constr.setAccessible(true);
} catch (NoSuchMethodException ex) {
try {
constr =
String.class.getDeclaredConstructor(int.class, int.class, char[].class);
constr.setAccessible(true);
} catch (NoSuchMethodException ex2) {
ex2.addSuppressed(ex);
LOG.info("building String from char[] fast not supported", ex2);
constr = null;
} catch (SecurityException ex2) {
ex2.addSuppressed(ex);
throw new RuntimeException(ex2);
}
} catch (SecurityException ex) {
throw new RuntimeException(ex);
}
return constr;
}
});
if (prConstr == null) {
PROTECTED_STR_CONSTR_PARAM_TYPES = null;
PROTECTED_STR_CONSTR_HANDLE = null;
} else {
PROTECTED_STR_CONSTR_PARAM_TYPES = prConstr.getParameterTypes();
try {
PROTECTED_STR_CONSTR_HANDLE = lookup.unreflectConstructor(prConstr);
} catch (IllegalAccessException ex) {
throw new ExceptionInInitializerError(ex);
}
}
}
