Why does the JVM allow be to pass a B[] to a method that expects an A[]?

Why does the JVM allow be to pass a B[] to a method that expects an A[]?

By : Keith Petrone
Date : November 21 2020, 09:01 AM
I think the issue was by ths following , After Type Erasure, T will be turned into Object since you didn't specify a bound on T. So, there is no problem at runtime assigning any type of array to genericTypeArray, which is now of type Object[] or calling the function setArray(...), which now also accepts an argument of type Object[]. Also, your get(...) method will simply return an Object.
Trouble starts when you access elements in the array with a wrong type expectation, since this might lead to (implicit or explicit) illegal type casts, for example by assigning the value returned by get(...) to a variable of type A.
code :
public T[] getArray() {
    return genericTypeArray;
BrokenGenerics<A> aBreaker = new BrokenGenerics<A>(new A("1"));
A[] array = aBreaker.getArray();
array = aBreaker.getArray(); // ClassCastException here!
private static class C extends BrokenGenerics<A> {

    public C(A... initArray) {

    public void printFirst() {
        A[] result = genericTypeArray; // ClassCastException here!
C cBreaker = new C(new A("1"));

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In Scala, how can I pass null to a Java method that expects Long?

In Scala, how can I pass null to a Java method that expects Long?

By : Mohammad Khaled
Date : March 29 2020, 07:55 AM
I think the issue was by ths following , I have a Java method that accepts a Long value: , I can't reproduce that here.
code :
public class JavaTst {
    public void setValue(Long value) {}
scala> new JavaTst
res0: JavaTst = JavaTst@4e229e

scala> res0.setValue(null)

res0.setValue(calcValue.map(new java.lang.Long(_)).getOrElse(null))
How to pass null to method that expects long or int?

How to pass null to method that expects long or int?

By : Raoul Duke
Date : March 29 2020, 07:55 AM
With these it helps The problem is that int and long are primitives. You can't pass null to a primitive value.
You can certainly use the wrapper classes Integer and Long instead of long and int in your method signature.
Pass null to a method expects Long

Pass null to a method expects Long

By : EDS
Date : March 29 2020, 07:55 AM
I hope this helps you . Since you can't change the signature, consider the mistake of Thinking Option[Foo] is the only/most natural way to express a missing function argument.
If the param to your function is a lower bound, then Long.MinValue might be a natural default.
How to pass an array to an objc method that expects var args (eg ...')

How to pass an array to an objc method that expects var args (eg ...')

By : user6482579
Date : March 29 2020, 07:55 AM
To fix this issue There is no easy way to do this, because how arguments are passed goes into the ugly details of the particular system's calling ABI, and you have to know e.g. how many arguments are put into registers, and how to deal with remaining arguments, etc. And this will involve assembly and it cannot be done in a general way.
Generally, any API that has a method or function that takes varargs like this, also will either
Is there any way to pass an NSArray to a method that expects a variable number of arguments, such as +stringWithFormat:

Is there any way to pass an NSArray to a method that expects a variable number of arguments, such as +stringWithFormat:

By : user3762644
Date : March 29 2020, 07:55 AM
Hope this helps (Edit: This worked back in the GCC days. It doesn't under Clang as of Xcode 4.6.)
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