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This noncompliant code example explicitly invokes run() in the context of the current thread.:

Code Block

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public final class Foo implements Runnable {
  @Override public void run() {
    // ...
  }

  public static void main(String[] args) {
    Foo foo = new Foo();
    new Thread(foo).run();
  }
}

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This compliant solution correctly uses the start() method to tell the Java runtimes runtime to start a new thread.:

Code Block

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public final class Foo implements Runnable {
  @Override public void run() {
    // ...
  }

  public static void main(String[] args) {
    Foo foo = new Foo();
    new Thread(foo).start();
  }
}

Exceptions

THI00-J-EX0: The run() method may be directly invoked during unit testing. Note that this method cannot be used to test a class for multithreaded use.

Given a Thread object that has been was constructed with a runnable argument, when invoking the Thread.run() method, the Thread object may be cast to Runnable to eliminate analyzer diagnostics.:

Code Block

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public void sampleRunTest() {

  Thread thread = new Thread(new Runnable() {
      @Override public void run() {
        // ...
      }
    });
  
  ((Runnable) thread).run();  // THI00-J-EX0: Does not start a new thread

}

Casting a thread to Runnable before calling the run() method documents that the explicit call to Thread.run() is intentional. Adding an explanatory comment alongside the invocation is highly recommended.

THI00-J-EX1: Runtime system code involved in starting new threads is permitted to invoke a Thread object's run() method directly; this is an obvious necessity for a working Java runtime system. Note that the likelihood that this exception applies to user-written code is vanishingly small.

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Failure to start threads correctly can cause unexpected behavior.

Rule	Severity	Likelihood	Detectable

Remediation Cost

Repairable	Priority	Level
THI00-J	Low

low

Probable

probable

Yes

medium

Yes

P4

P6

L3

L2

Automated Detection

Automated detection of direct invocations of Thread.run() methods is straightforward. Sound automated determination of which specific invocations are permitted may be infeasible. Heuristic approaches may be useful.

Tool

Version

Checker

Description

CodeSonar

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