16f6c0aecf
Inline adoc files when they are included exactly once. Also fix language tags because this inlining gives us better information on what language the code is written in.
63 lines
1.9 KiB
Plaintext
63 lines
1.9 KiB
Plaintext
== Why is this an issue?
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A Single Abstract Method (SAM) interface is a Java interface containing only one method. The Java API is full of SAM interfaces, such as ``++java.lang.Runnable++``, ``++java.awt.event.ActionListener++``, ``++java.util.Comparator++`` and ``++java.util.concurrent.Callable++``. SAM interfaces have a special place in Java 8 because they can be implemented using Lambda expressions or Method references.
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Using ``++@FunctionalInterface++`` forces a compile break when an additional, non-overriding abstract method is added to a SAM, which would break the use of Lambda implementations.
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*Note* that this rule is automatically disabled when the project's ``++sonar.java.source++`` is lower than ``++8++``.
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=== Noncompliant code example
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[source,java]
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----
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public interface Changeable<T> {
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public void change(T o);
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}
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----
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=== Compliant solution
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[source,java]
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----
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@FunctionalInterface
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public interface Changeable<T> {
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public void change(T o);
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}
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----
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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Annotate the "XXXX" interface with the "@FunctionalInterface" annotation. [(sonar.java.source not set. Assuming 8 or greater.)]
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'''
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== Comments And Links
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(visible only on this page)
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=== on 25 Feb 2014, 23:31:07 Freddy Mallet wrote:
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Is implemented by \http://jira.codehaus.org/browse/SONARJAVA-462
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=== on 26 Feb 2014, 01:50:25 Ann Campbell wrote:
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I expanded a little here. Double-check me, please.
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=== on 23 Oct 2015, 13:25:55 Michael Gumowski wrote:
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\[~ann.campbell.2] I activated the rule by default, as we are now able to execute it only if the java version of the source code is java8+!
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I also added code tags into the description.
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=== on 19 Nov 2015, 17:25:40 Michael Gumowski wrote:
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Fixed typo in error message (see commit: \https://github.com/SonarSource/sonar-java/commit/ef867a2aa66d071227bb00c2449cef2cceb8a738)
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endif::env-github,rspecator-view[]
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