Graph/39e1bb3c-c7dd-465d-962e-346b6aad2286

Domainunvalidated

Generics

39e1bb3c-c7dd-465d-962e-346b6aad2286

Generics

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Updated5/1/2026

PageRank0.0000

Effectiveness0.000

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50 linked nodes

PERTAIN_TOProblem

I need a way to sandbox the code and limit its permissions. — dynamically loading and executing third-party code. Outcome: there are (currently) no alternatives for running untrusted Java code within a Java application.

PERTAIN_TOProblem

I tried using `[key in FormData]:string`, but that forces me to have all fields, and not just one. Tension: I want to create a type that could encase the following: `{field1: string}` or `{field2: string}` and all other potential fields. Outcome: I don't want to make them all ignorable with `?`.

PERTAIN_TOSolution

You can use Typescript Mapped Types and declare a type like this — Since you want at least one key.

PERTAIN_TOAnswer

so-79357675

PERTAIN_TOProblem

`Nodes` which are the React components that should corresponds to node types from `nodeTypes` prop — two props in my Component: `nodeTypes` prop which is of `NodeType[]` type (list of node types) and second prop `Nodes`. Tension: so it should be an object whose keys are `NodeType`s from `nodeTypes` prop.

PERTAIN_TOSolution

you can use the following type for the `Nodes` prop — To infer the type of the `nodeTypes` prop, which is an array, for the `Nodes` prop. Tension: `Nodes` prop, which should represent an item from the `nodeTypes` array.

PERTAIN_TOAnswer

so-78684188

PERTAIN_TOProblem

What does 0 mean in this case? — In Java we have toArray() method. Tension: I need to pass it to parameters like this. Outcome: `new AnotherClass[0]` will create an array with 0 elements.

PERTAIN_TOSolution

`SomeList.toArray(...)` will first check if the array is big enough to fit the elements — Java we have toArray() method. Tension: You might prefer to do `someList.toArray(new AnotherClass[someList.size()])`. Outcome: `new AnotherClass[0]` will create an array with 0 elements.

PERTAIN_TOAnswer

so-79725090

PERTAIN_TORootCause

com.vaadin.flow.component.AbstractField & com.vaadin.flow.component.Focusable & com.vaadin.flow.component.Focusable & com.vaadin.flow.component.shared.InputField — Stream.of(this, part1, part2, part3).forEach(c -> c.addFocusListener(event -> this.focused = true));. Tension: I see that `CustomField` now effectively inherits from `HasValue` twice. Outcome: adding a focus listener to `this` and each part using this line.

PERTAIN_TOProblem

I'm upgrading a Vaadin 23.2 app to Vaadin 24.8. I have a compilation error on one of my components. Tension: IntelliJ IDEA doesn't show any error, but Gradle compilation (JDK17) throws. Outcome: when I remove the class the issue is gone.

PERTAIN_TOProblem

When I hover over the `c` lambda parameter, IntelliJ IDEA shows its type: — I'm adding a focus listener to `this` and each part using this line:. Tension: com.vaadin.flow.component.AbstractField & com.vaadin.flow.component.Focusable & com.vaadin.flow.component.Focusable & com.vaadin.flow.component.shared.InputField. Outcome: Commenting out that line makes the error go away.

PERTAIN_TOSolution

I can just add the focus listerens to `this` and the parts separately: — `this` and each part using this line:. Outcome: `this.addFocusListener(event -> this.focused = true); Stream.of(part1, part2, part3).forEach(c -> c.addFocusListener(event -> this.focused = true));.

PERTAIN_TOSolution

Or I can first assign the `Stream` to a simpler type instead of the enormous inferred type: — Or I can first assign the `Stream` to a simpler type instead of the enormous inferred type:. Outcome: `Stream> stream = Stream.of(this, part1, part2, part3); stream.forEach(c -> c.addFocusListener(event -> this.focused = true));.

PERTAIN_TOAnswer

so-79725907

PERTAIN_TORootCause

because of "type erasure," — dealing with types like `Consumer` whose specifics are erased before runtime. Tension: would need to write a dozen "helper functions" like this.

PERTAIN_TOProblem

calling Lambda expressions invariably leads to "unchecked call" warnings — While porting my BASIC byte-code interpreter from Python to Java. Tension: I couldn't figure out how to make Java's type system happy. Outcome: Is it even possible to avoid an "unchecked cast" when dealing with types like `Consumer` whose specifics are erased before runtime?

PERTAIN_TOSolution

Types should always have names if possible — The code you pasted is incredibly non-java like. Tension: Your `bcode` array fails all these rules. Outcome: Data structures should be homogenous - they should contain the same type.

PERTAIN_TOAnswer

so-79541344

PERTAIN_TORootCause

in `get` the `T` return parameter is derived from the `T` class parameter. — raw type is used in `Sub extends Super`. Tension: They must be equal. In this case equal to the concrete class before erasure. Outcome: they must be equal. In this case equal to the concrete class before erasure.

PERTAIN_TOProblem

From simply looking at the code, `get` giving an error is obvious to me. — raw type is used in `Sub extends Super`. Tension: For backward compatibility, Java allows a non-generic method in subclass to override a generic method in superclass as long as they have the same erasure. Outcome: `get` giving an error is obvious to me.

PERTAIN_TOSolution

you can fix the method parameter to something that's compatible (something broader) — `transform` compiles. Tension: They must be equal. Outcome: you can fix the method parameter to something that's compatible (something broader).

PERTAIN_TOAnswer

so-79403151

PERTAIN_TOSolution

if `m1` overrides `m2`, the signature of `m1` must be a subsignature of the signature of `m2` — For `R1` and `R2` that are reference types. Tension: `Object get()` is not return-type-substitutable for `T get()`.

PERTAIN_TOAnswer

so-79404144

PERTAIN_TOProblem

incompatible types: java.util.List cannot be converted to java.util.List — List strings = new ArrayList<>(); List objs = (List)strings;. Tension: I would expect this to fail to compile for the same reason, but it doesn't. Outcome: I can even use it with the same classes.

PERTAIN_TOAnswer

so-79392036

PERTAIN_TOSolution

Create a forwarding Iterator<SuperClass> wrapper that delegates hasNext() and next() to the underlying Iterator<SubClass>

PERTAIN_TOSolution

Cast to raw Iterator if you accept unchecked warnings

PERTAIN_TOAnswer

so-79390722

PERTAIN_TOSolution

I’m trying to use GraalVM to execute JavaScript code that makes a REST call using Java. — execute JavaScript code that makes a REST call.

PERTAIN_TOProblem

GraalVM JavaScript is not installed, so Context.newBuilder("js") and ScriptEngineManager.getEngineByName("JavaScript") fail

PERTAIN_TOAnswer

so-79300658

PERTAIN_TORootCause

private Class getGenericClass().

PERTAIN_TOProblem

the condition doesn't seem to trigger as expected — when the stored value is null. Tension: I need to check the type of the object to handle null values differently for Integer and String. Outcome: it always falls through to returning null.

PERTAIN_TOSolution

Use a constructor parameter or type token to retain the generic type instead of deriving it from a null value

PERTAIN_TOAnswer

so-79245454

PERTAIN_TOProblem

error: unreported exception Exception; must be caught or declared to be thrown — in try-with-resources context. Tension: exception thrown from implicit call to close() on resource variable 'test'.

PERTAIN_TOSolution

Option 3 for the answer here would be to define your own implementation of `java.lang.AutoCloseable` — in try-with-resources context. Tension: the method `close()` does not declare an exception at all. Outcome: try( final MyCloseable test = () -> System.out.println( "Closing" ) ).

PERTAIN_TOAnswer

so-79095870

PERTAIN_TOProblem

a += generate() should move elements but a += b should copy elements

PERTAIN_TOSolution

Use `std::views::as_rvalue(rhs)` for rvalue inputs and `lhs.append_range(rhs)` for lvalues

PERTAIN_TOAnswer

so-79802439

PERTAIN_TOProblem

I would like to define a macro that would take number of arguments in function template `ARGS_COUNT` — If it's possible, I would like to define a macro. Tension: I want this, since I would like to refer to `Fi` sometimes, instead of bloating function definition.

PERTAIN_TOSolution

Provide a limited family of macros for fixed arities such as 0 to 10, and add more copies if you need higher arities

PERTAIN_TOAnswer

so-79804837

PERTAIN_TOProblem

not all types that `value` can hold support addition — I have a generic struct Node that holds any value.

PERTAIN_TOSolution

then you might use `std::visit` for the multi-dispatch. Tension: Not addable. Outcome: if constexpr (requires { t1 + t2; } ).

PERTAIN_TOAnswer

so-79800387

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