28 lines
894 B
Plaintext
28 lines
894 B
Plaintext
Java 15 introduced feature of ``++sealed++`` classes. With ``++sealed++`` classes and interfaces you can specify a strict hierarchy of types and restrict possible inheritance.
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Although this feature can help to make code safer, it is not applicable everywhere. Functional interfaces can not be sealed. This means that if an interface with a single abstract method is declared with a ``++sealed++`` keyword, its implementation can't be replaced with a lambda.
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This rule reports an issue when an interface with a single abstract method is marked ``++sealed++``.
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== Noncompliant Code Example
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----
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public sealed interface F permits ... { // Noncompliant
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void f();
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}
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----
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== Compliant Solution
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----
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public interface F { // Compliant
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void f();
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}
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----
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== See
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* https://docs.oracle.com/javase/specs/jls/se16/preview/specs/sealed-classes-jls.html#jls-8.1.1.2[Sealed classes specification]
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