37 lines
1.8 KiB
Plaintext
37 lines
1.8 KiB
Plaintext
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== Why is this an issue?
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The `Thread` class has some methods that are used to monitor and manage its execution.
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With the introduction of virtual threads in Java 21, there are three of these methods that behave differently
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between the standard platform threads and the virtual ones.
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For virtual threads:
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* `Thread.setDaemon(boolean)` will throw an `IllegalArgumentException` if `false` is passed as an argument as a virtual thread daemon status is always true.
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* `Thread.setPriority(int priority)` will never change the actual priority of a virtual thread, which is always equal to `Thread.NORM_PRIORITY`
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* `Thread.getThreadGroup()` will return a dummy "VirtualThreads" group that is empty and should not be used
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This rule reports an issue when one of these methods is invoked on a virtual thread.
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=== Code examples
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==== Noncompliant code example
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[source,java]
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----
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Thread t = Thread.ofVirtual().unstarted(()->{/* some task */});
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t.setPriority(1); // Noncompliant; virtual threads' priority cannot be changed
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t.setDaemon(false); // Noncompliant; will throw IllegalArgumentException
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t.setDaemon(true); // Noncompliant; redundant
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t.start();
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var threadGroup = t.getThreadGroup(); // Noncompliant; virtual thread groups should not be used
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----
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== Resources
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=== Documentation
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* Java Documentation - https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/Thread.html#setDaemon(boolean)[Thread.setDaemon]
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* Java Documentation - https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/Thread.html#setPriority(int)[Thread.setPriority]
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* Java Documentation - https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/Thread.html#getThreadGroup()[Thread.getThreadGroup]
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* Java Documentation - https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/ThreadGroup.html#virtualthreadgroup[Virtual threads group]
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