The compatibility rules of Java function generics ensure type safety. Rules include: same type parameter lists, same type parameter bounds, and contravariant and covariant type parameters. For example,
Compatibility rules for Java function generics
Java generic functions allow us to write code in a type-safe manner, But not following the correct compatibility rules can lead to compile-time errors. Let’s sort out the rules to avoid such problems.
Rule 1: The type parameter lists are the same
Only function types with the same parameter list are compatible. So the following example will result in an error:
publicvoid func1(T v) {} public void func2(U v) {}
Rule 2: Type parameters have the same bounds
Bounds define the allowed values of a generic type. Functions are incompatible if they have different bounds for parameters of the same type. For example:
public> void func1(T v) {} public void func2(T v) {}
Rule 3: Contravariant and covariant type parameters
> > Practical case
Consider the following code:
publicvoid func1(T t) { // 代码... } public void func2(Cat c) { // 代码... }
func1Expects anAnimalor an instance of its subclass.func2Expects aCatinstance. SinceCatextendsAnimal,func1is compatible withfunc2and can receiveCattype parameters.
Conclusion
It is crucial to follow the compatibility rules for function generics to avoid compile-time errors and ensure type safety.
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