ThreadJoinLoop
Thread.join needs to be surrounded by a loop until it succeeds, as in Uninterruptibles.joinUninterruptibly.

Category
Severity
WARNING
Maturity

The problem

Thread.join() can be interrupted, and so requires users to catch InterruptedException. Most users should be looping until the join() actually succeeds.

Suppression

Suppress false positives by adding an @SuppressWarnings("ThreadJoinLoop") annotation to the enclosing element.


Positive examples

ThreadJoinLoopPositiveCases.java

/*
 * Copyright 2017 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.errorprone.bugpatterns.testdata;

/** @author mariasam@google.com (Maria Sam) on 7/10/17. */
class ThreadJoinLoopPositiveCases {

  public void basicCase(Thread thread) {
    try {
      // BUG: Diagnostic contains: Uninterruptibles.joinUninterruptibly(thread)
      thread.join();
    } catch (InterruptedException e) {
      // ignore
    }
  }

  public void emptyInterruptedFullException(Thread thread) {
    try {
      // BUG: Diagnostic contains: Uninterruptibles.joinUninterruptibly(thread)
      thread.join();
    } catch (InterruptedException e) {
      // ignore
    }
  }

  public void emptyException(Thread thread) {
    try {
      // BUG: Diagnostic contains: Uninterruptibles.joinUninterruptibly(thread)
      thread.join();
    } catch (Exception e) {
      // ignore
    }
  }

  public void whileLoop(Thread thread) {
    while (true) {
      try {
        // BUG: Diagnostic contains: Uninterruptibles.joinUninterruptibly(thread)
        thread.join();
      } catch (InterruptedException e) {
        // ignore
      }
    }
  }

  public void whileLoopCheck(Thread thread) {
    while (thread != null) {
      try {
        // BUG: Diagnostic contains: Uninterruptibles.joinUninterruptibly(thread)
        thread.join();
      } catch (InterruptedException e) {
        // ignore
      }
    }
  }

  public void whileLoopVariable(Thread thread, boolean threadAlive) {
    while (threadAlive) {
      try {
        // BUG: Diagnostic contains: Uninterruptibles.joinUninterruptibly(thread)
        thread.join();
        threadAlive = false;
      } catch (InterruptedException e) {
        // ignore
      }
    }
  }

  public void basicLoopOtherStatements(Thread thread) {
    while (7 == 7) {
      System.out.println("test");
      try {
        // BUG: Diagnostic contains: Uninterruptibles.joinUninterruptibly(thread)
        thread.join();
      } catch (InterruptedException e) {
        // ignore
      }
    }
  }

  public void breakStatement(Thread thread) {
    while (7 == 7) {
      try {
        // BUG: Diagnostic contains: Uninterruptibles.joinUninterruptibly(thread)
        thread.join();
        break;
      } catch (InterruptedException e) {
        // ignore
      }
    }
  }

  private void whileLoopBreak(Thread thread) {
    while (true) {
      try {
        // BUG: Diagnostic contains: Uninterruptibles.joinUninterruptibly(thread)
        thread.join();
        break;
      } catch (InterruptedException e) {
        /* try again */
      }
    }
  }

  private void whileLoopThreadAlive(Thread thread) {
    while (thread.isAlive()) {
      try {
        // BUG: Diagnostic contains: Uninterruptibles.joinUninterruptibly(thread)
        thread.join();
      } catch (InterruptedException e) {
        // Ignore
      }
    }
  }

  public void multipleStatements(Thread thread, boolean isAlive) {
    try {
      // BUG: Diagnostic contains: Uninterruptibles.joinUninterruptibly(thread)
      thread.join();
      isAlive = false;
    } catch (InterruptedException e) {
      // ignore
    }
  }

  private void arrayJoin(Thread[] threads) {
    for (int i = 0; i < threads.length; i++) {
      try {
        // BUG: Diagnostic contains: Uninterruptibles.joinUninterruptibly(threads[i])
        threads[i].join();
      } catch (InterruptedException e) {
        // ignore
      }
    }
  }

  class MyThread extends Thread {

    public void run() {
      try {
        // BUG: Diagnostic contains: Uninterruptibles.joinUninterruptibly(this)
        join();
      } catch (InterruptedException e) {
        // ignore
      }
    }

    public void whileInThread() {
      while (isAlive()) {
        try {
          // BUG: Diagnostic contains: Uninterruptibles.joinUninterruptibly(this)
          join();
        } catch (InterruptedException e) {
          // Ignore.
        }
      }
    }
  }
}

ThreadJoinLoopPositiveCases_expected.java

/*
 * Copyright 2017 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.errorprone.bugpatterns.testdata;

import com.google.common.util.concurrent.Uninterruptibles;

/** @author mariasam@google.com (Maria Sam) on 7/10/17. */
class ThreadJoinLoopPositiveCases {

  public void basicCase(Thread thread) {
    Uninterruptibles.joinUninterruptibly(thread);
  }

  public void emptyInterruptedFullException(Thread thread) {
    Uninterruptibles.joinUninterruptibly(thread);
  }

  public void emptyException(Thread thread) {
    Uninterruptibles.joinUninterruptibly(thread);
  }

  public void whileLoop(Thread thread) {
    Uninterruptibles.joinUninterruptibly(thread);
  }

  public void whileLoopCheck(Thread thread) {
    Uninterruptibles.joinUninterruptibly(thread);
  }

  public void whileLoopVariable(Thread thread, boolean threadAlive) {
    Uninterruptibles.joinUninterruptibly(thread);
  }

  public void basicLoopOtherStatements(Thread thread) {
    while (7 == 7) {
      System.out.println("test");
      Uninterruptibles.joinUninterruptibly(thread);
    }
  }

  public void breakStatement(Thread thread) {
    Uninterruptibles.joinUninterruptibly(thread);
  }

  private void whileLoopBreak(Thread thread) {
    Uninterruptibles.joinUninterruptibly(thread);
  }

  private void whileLoopThreadAlive(Thread thread) {
    Uninterruptibles.joinUninterruptibly(thread);
  }

  public void multipleStatements(Thread thread, boolean isAlive) {
    Uninterruptibles.joinUninterruptibly(thread);
  }

  private void arrayJoin(Thread[] threads) {
    for (int i = 0; i < threads.length; i++) {
      Uninterruptibles.joinUninterruptibly(threads[i]);
    }
  }

  class MyThread extends Thread {

    public void run() {
      Uninterruptibles.joinUninterruptibly(this);
    }

    public void whileInThread() {
      Uninterruptibles.joinUninterruptibly(this);
    }
  }
}

Negative examples

ThreadJoinLoopNegativeCases.java

/*
 * Copyright 2017 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.errorprone.bugpatterns.testdata;

import java.util.List;

/** @author mariasam@google.com (Maria Sam) on 7/10/17. */
public class ThreadJoinLoopNegativeCases {

  public void basicCase(Thread thread) throws InterruptedException {
    thread.join();
  }

  public void inIf(Thread thread) {
    try {
      if (7 == 7) {
        thread.join();
      }
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
  }

  public void basicCaseTry(Thread thread) {
    try {
      thread.join();
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
  }

  public void basicCaseWhile(Thread thread, List<String> list) {
    while (list.size() == 7) {
      try {
        thread.join();
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    }
  }

  public void basicCaseFor(Thread thread, List<String> list) {
    for (int i = 0; i < list.size(); i++) {
      try {
        thread.join();
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    }
  }

  public void basicCaseForEach(Thread thread, List<String> list) {
    for (String str : list) {
      try {
        thread.join();
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    }
  }

  public void multipleCatches(Thread thread, int[] arr) {
    try {
      thread.join();
      int test = arr[10];
    } catch (ArrayIndexOutOfBoundsException e) {
      // ignore
    } catch (InterruptedException e) {
      System.out.println("test");
    }
  }

  public void fullInterruptedFullException(Thread thread) {
    try {
      thread.join();
    } catch (InterruptedException e) {
      e.printStackTrace();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  public void justException(Thread thread) {
    try {
      thread.join();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  public void multipleMethodInvocations(Thread thread, Thread thread2) {
    try {
      thread.join();
      thread2.join();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  public void tryFinally(Thread thread) {
    try {
      thread.join();
    } catch (InterruptedException e) {
      // ignore
    } finally {
      System.out.println("test finally");
    }
  }

  public void tryAssigningThread(Thread thread) {
    while (true) {
      try {
        thread.join();
        thread = null;
      } catch (InterruptedException e) {
        // ignore
      }
    }
  }
}