I have this code in Foo.scala
object Foo extends App
{
def bar() = () => println("hello")
bar()()
}
If I run
scalac Foo.scala
I obtain three .class files:
Foo$.class
Foo$delayedInit$body.class
Foo.class
If then I run
javap 'Foo$.class'
I get on stdout
Compiled from "Foo.scala"
public final class Foo$ implements scala.App {
public static Foo$ MODULE$;
public static {};
public java.lang.String[] args();
public void delayedInit(scala.Function0<scala.runtime.BoxedUnit>);
public void main(java.lang.String[]);
public long executionStart();
public java.lang.String[] scala$App$$_args();
public void scala$App$$_args_$eq(java.lang.String[]);
public scala.collection.mutable.ListBuffer<scala.Function0<scala.runtime.BoxedUnit>> scala$App$$initCode();
public void scala$App$_setter_$executionStart_$eq(long);
public final void scala$App$_setter_$scala$App$$initCode_$eq(scala.collection.mutable.ListBuffer<scala.Function0<scala.runtime.BoxedUnit>>);
public scala.Function0<scala.runtime.BoxedUnit> bar();
public static final void $anonfun$bar$1();
public final void delayedEndpoint$Foo$1();
}
As you can see the lambda that is returned from the bar method is
compiled into public static final void $anonfun$bar$1();
I would like to be able to have all the lambda used in my scala code compiled as private method instead of public ones (it shouldn't be a problem when those functions are just local method variables, since they can only be accessed from within the method in which they are declared). Is there a way to achieve that?
P.S.
I'm asking because I'm using Scala to create Java EE's EJB classes and EJB classes used with no-interface view cannot have methods that are both public and final (it must be possible to instantiate a subclass that overrides all the public methods to create a proxy)
Related
While studying interface I came along this weird behaviour
When I am running this
int num=20;
public void sound();
public void eat();
}
class Dog implements Animal{
public void sound(){
System.out.println("Wooof!!!!!!!");
}
public void eat(){
System.out.println("Food");
}
}
public class Main{
public static void main(String[]args){
Dog dog=new Dog();
dog.sound();
dog.eat();
System.out.println(Dog.num);
//System.out.println(Dog.num1);
}
}
It runs fine while If I declare a no static variable with same name i.e. num as of the one in interface like this
interface Animal{
int num=20;
public void sound();
public void eat();
}
class Dog implements Animal{
int num=10;
public void sound(){
System.out.println("Wooof!!!!!!!");
}
public void eat(){
System.out.println("Food");
}
}
public class Main{
public static void main(String[]args){
Dog dog=new Dog();
dog.sound();
dog.eat();
System.out.println(Dog.num);
//System.out.println(Dog.num1);
}
}
It gives this error Main.java:22: error: non-static variable num cannot be referenced from a static context
My question was since one from interface is static and is of class level why the child class i.e. Dog compilation fails when I declare a non static instance level variable.
The problem is your are trying to access Dog class into System.out.println(). Not the variable dog where the class has been initialized.
If variable num is not static is impossible to read it without initialize the class, so if you want to do Dog.num, that variable has to be static.
If you don't add the variable into Dog class, the value will be declared in the interface, but if the variable exists in the class, the compiler will try read that.
I'm running a C# project on VS2019 with the following code structure:
In the Class1.cs file:
public class Class1
{
public class MyClass2 : Class2
{
...
}
private void RunAlgorithm<T>() where T : Class2, new()
{
T argInstance = new T();
...
}
static void Main(string[] args)
{
RunAlgorithm<MyClass2>();
}
}
In the Class2.cs file:
public class Class2
{
public Class2() { }
public string setParameters { get; set; }
}
I'm getting the following error for the line RunAlgorithm<MyClass2>();
'Class1.MyClass2' must be a non-abstract type with a public
parameterless constructor in order to use it as parameter 'T' in the
generic type or method 'Class1.RunAlgorithm()'
even if I change it to Public, the error persists
Well, minimally, it'll have to be protected so that MyClass can access it..
https://dotnetfiddle.net/XFeEdQ
public class Class1
{
class MyClass2 : Class2
{
}
private void RunAlgorithm<T>() where T : Class2, new()
{
T argInstance = new T();
}
public static void Main(string[] args)
{
new Class1().RunAlgorithm<MyClass2>();
}
}
public class Class2
{
protected Class2() { }
public string setParameters { get; set; }
}
So your "Class1.MyClass2
must have a public parameterless constructor" message is saying that your MyClass needs a constructor. Mine above has such a constructor even though it's not in the code; in the absence of the developer providing a constructor the compiler provides one that does nothing other than call the base parameterless constructor...
...which leads me to the next point; your MyClass2 extends Class2, and hence Class2's constructor needs to be accessible to it. While Class2's constructor is private, MyClass2's constructor can't call it. Every constructor on c# has to either call another constructor or a base constructor. If you don't specify which, the compiler will insert a call to base() for you, which will fail if the base constructor is inaccessible
For this all to work out you need a public parameterless constructor in MyClass2:
public MyClass2():base(){}
or without the base(compiler will add the base call)
or blank (compiler will add all of it)
and you need something that makes Class2's constructor accessible to MyClass2, ie declaring Class2's constructor as public or protected
I had following code
public interface IFoo
{
void Execute();
}
public abstract class FooBar: IFoo
{
public void Execute()
{
OnExecute();
}
public abstract void OnExecute();
}
and following test case to test the Execute() method
[Fact]
public void When_execute_method_called_Expect_executionTime_is_set()
{
var sutMethod = A.Fake<FooBar>();
A.CallTo(sutMethod).
Where(x => x.Method.Name == "OnExecute").
Invokes(x => Thread.Sleep(100)));
sutMethod.Execute();
Assert.NotEqual(0, sutMethod.Result.ExecutionTime.Ticks);
}
sutMethod.Execute(); call would go to FooBar.Execute()
later I decided to make the interface into an abstract class
public abstract class IFoo
{
public abstract void Execute();
}
public abstract class FooBar:IFoo
{
public override void Execute()
{
OnExecute();
}
public abstract void OnExecute();
}
Now sutMethod.Execute(); call does not invoke FooBar.Execute()
I thought FakeItEasy would handles interface and abstract classes as equal.What am I missing?
Update
# Blair Conrad provided the reasoning for the behaviour
Is it possible to make minimal changes to the test case to get the original behaviour back?
thanks
The difference is due to the overrideability of the method Execute on FooBar.
FakeItEasy can only override virtual members, abstract members, or interface members.
In your original example, when IFooBar is an interface and FooBar implements it, Execute is a concrete method. It's not virtual, nor is it abstract. Thus FakeItEasy can't intercept calls to it, and the original method is executed.
Once you change IFooBar to an abstract class, you have an abstract IFooBar.Execute, which you override in FooBar. As such, FooBar.Execute is now virtual and can be intercepted by FakeItEasy. Which it does, so your implementation is not called.
Following addition help solve the issue
A.CallTo(() => sutMethod.Execute()).CallsBaseMethod();
This calls the virtual method Executeof FooBar
I am trying to send over MyClass through RPC, but am getting :
Type MyClass was not assignable to 'com.google.gwt.user.client.rpc.IsSerializable' and did not have a custom field serializer.For security purposes, this type will not be serialized.
I have looked at GWT - occasional com.google.gwt.user.client.rpc.SerializationException and tried their solution, but it did not work.
The difference is that MyClass is located in another project.
The project structure is:
MyApiProject
-contains MyClass
MyClientProject
MyServerProject
I have also tried passing an enum through the RPC from MyApiProject, which also failed.
public class MyClass
implements Serializable
{
private static final long serialVersionUID = 5258129039653904120L;
private String str;
private MyClass()
{
}
public MyClass(String str)
{
this.str = str;
}
public String getString()
{
return this.str;
}
}
in the RemoteService I have:
mypackage.MyClass getMyClass();
in the RemoteServiceAsync I have:
void getMyClass(AsyncCallback<mypackage.MyClass> callback);
I had to change implements Serializable to implements IsSerializable
This usually pops up when you are using another type inside of your class that is not serializable. Check the properties of your class and make sure they are all serializable, post the code of MyClass here and I can look at it as well.
I believe GWT requires an RPC serializable class to also have a public no-argument constructor.
Try removing
private MyClass()
{
}
or set it to
public MyClass()
{
}
I have a JUnit test that I run on one class, but I recently wrote an emulated version for GWT. Since the specification is the same, I would like to use the same test case, but I want it to run in the GWT environment, which would typically be accomplished by extending GWTTestCase.
I really want to avoid any copy/paste nonsense, because there are likely to be added tests in the future, which I should not be burdened with copying later.
How can I import/inherit my standard unit test to be run as either a regular test case or a GWT test case?
I have found the solution to this problem.
If you extend the original test with GWTTestCase, you can override getModuleName to return null. This tells GWTTestCase to run as a normal pure java test (no translation at all).
You can then extend this test case with one that overrides getModuleName to return a module name, and the same tests will be run with translation.
Basically:
public class RegularTest extends GWTTestCase {
#Override
public String getModuleName() { return null; }
public void testIt() {...}
}
...and the GWT version...
public class GwtTest extends RegularTest {
#Override
public String getModuleName() { return "some.module"; }
}
The downside to this is that it forces you to use JUnit3 style tests, which I find a little annoying, but it beats the alternative.
I think there is no easy way .. But you can extract an interface of your junit test, gwt test case and junit test case implements this interface. You can create a third class for implementation, all test call methods of gwt test case and junit test are delegated to this implementation class.
public interface IRegularTest {
public void testSomething();
public void testSomething2();
}
public class RegularTestImpl implements IRegularTest {
public void testSomething(){
// actual test code
}
public void testSomething2(){
// actual test code
}
}
public class RegularTest extends TestCase implements IRegularTest {
IRegularTest impl = new RegularTestImpl();
public void testSomething(){
impl.testSomething
}
public void testSomething2(){
}
}
public class GwtTest extends TestCase implements IRegularTest {
IRegularTest impl = new RegularTestImpl();
public void testSomething(){
impl.testSomething
}
public void testSomething2(){
}
}