logo
down
shadow

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();
System.out.println(array[0]);
System.out.println(aBreaker.getType());
breakThis(aBreaker);
array = aBreaker.getArray(); // ClassCastException here!
System.out.println(array[0]);
System.out.println(aBreaker.getType());
private static class C extends BrokenGenerics<A> {

    public C(A... initArray) {
        super(initArray);
    }

    public void printFirst() {
        A[] result = genericTypeArray; // ClassCastException here!
        System.out.println(result[0]);
    }
}
C cBreaker = new C(new A("1"));
cBreaker.printFirst();
breakThis(cBreaker);
cBreaker.printFirst();


Share : facebook icon twitter icon
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.
JavaTst.java:
code :
public class JavaTst {
    public void setValue(Long value) {}
}
scala> new JavaTst
res0: JavaTst = JavaTst@4e229e

scala> res0.setValue(null)

scala>
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.)
Related Posts Related Posts :
  • How to query using objectify in Google App Engine app
  • List value is printing address instead of value
  • StringUtils.isBlank return false for null Strings
  • Sent parameter through PATCH android
  • i am not able to clear the code below given using throwable concept in java
  • How to get System time instead of Server time in java?
  • How to push json data into an arrya object in MONGO DB by java
  • Saving RelationshipEntity not working
  • Error on "instanceOf" when checking a subClass
  • Java - Splitting a image into 4 images
  • "Pinging" a server in Java
  • RoboGuice Proguard CreationException
  • Android Array list returns Null after adding values
  • Jar Executable what am I doing wrong?
  • How do I mitigate Connection leak triggered for connection com.mysql.jdbc.JDBC4Connection@11d08960,
  • How do i iterate values from a 2d array using conditions
  • Hide Button in CustomPagerAdapter
  • Java GC: does it ever make sense to call super.finalize() in a class that only extends Object?
  • 64bit HashMap in Java
  • Hibernate wildcard query on two columns
  • Want to Generate Auto Login Program Using Java
  • Spring security Oauth 2 with ajax login and form login
  • Parse findInBackground doesn't add to global arraylist?
  • Remove random item from ArrayList
  • in SpringMVC getMessage from i18n properties in a function outside the controller
  • How do I add JCheckBox next to each name that has been entered into an arraylist from a JTextField?
  • Return node ID along with complete node
  • InvocationTargetException. Cannot cast class X to class X. When invoked in Scala Imain through spark-submit
  • how to print elements of a 1D array into a N x N box
  • How to map csv file to pojo class in java
  • How, in Java, to encode default vhost %2F in URL/URI so it doesn't get changed to slash and fail to work
  • Tomcat 5.5 https configuration in Windows Server 2008 64bit
  • Enabling FIPS 140-2 compliance mode in MULE ESB
  • How to pass String PackageName to PkgName under parseXML() and run XMLParser class as a new activity when click on list
  • Error while creating spring -hibernate configuration file
  • Hand off control between java threads
  • NoClassDefFoundError: scala/collection/Seq
  • Getting stack overflow error on one machine but not the other on the same code
  • How can I loop AsyncAjaxRequest in GWT?
  • Failed to find provider info for urbanairship.provider
  • Android ListView Adapter Crash issue/Duplicates
  • Displaying Splash screen only once on user preference
  • Loop List<WebElement> doesn't stop despite no more WebElements
  • Check if pattern exists in a String
  • Swing - Key Problems (Arrow Keys, Tab, etc.) in GUIs with TextComponents
  • Why the solution for binary search tree validity is not working?
  • Double encrypting 2048 RSA?
  • create junit test for runnable class
  • Unable to read and sort information from a text file in Java
  • My device isn't getting detected in android studio (driver issue)
  • Representing a Graph in Java
  • How to XML mapping using jxls
  • Quick Sort stackoverflow error for large arrays
  • Parsing Apache Tika XML Output returns Unknown Tag
  • java simple UI loop, can't find bug
  • how to use greater than and less than in a single if statement in java
  • Error:(27, 13) Failed to resolve: com.antonyt.infiniteviewpager:library:1.0.0
  • Gradle dependencies on source set of different projects
  • Session Scope in Restful Spring Services
  • Java: Change a value in an overridden method of a different class to a value that was calculated in the class
  • shadow
    Privacy Policy - Terms - Contact Us © animezone.co