checker/tests/lock/Fields.java

import org.checkerframework.checker.lock.qual.*;

public class Fields {
  class MyClass {
    public Object field;
  }

  static @GuardedBy("Fields.class") MyClass lockedStatically;

  static synchronized void ssMethod() {
    lockedStatically.field = new Object();
  }

  @GuardedBy("lockingObject") MyClass locked;

  final Object lockingObject = new Object();

  synchronized void wrongLock1() {
    // locking over wrong lock
    // :: error: (lock.not.held)
    locked.field = new Object(); // error
  }

  synchronized void wrongLock2() {
    // locking over wrong lock
    synchronized (this) {
      // :: error: (lock.not.held)
      locked.field = new Object(); // error
    }
  }

  void rightLock() {
    synchronized (lockingObject) {
      locked.field = new Object();
    }

    // accessing after the synchronized object
    // :: error: (lock.not.held)
    locked.field = new Object(); // error
  }

  @Holding("lockingObject")
  void usingHolding() {
    locked.field = new Object();
  }

  @GuardedBy("this") MyClass lockedByThis;

  void wrongLocksb() {
    // without locking
    // :: error: (lock.not.held)
    lockedByThis.field = new Object(); // error

    synchronized (Fields.class) {
      // :: error: (lock.not.held)
      lockedByThis.field = new Object(); // error
    }
  }

  void rightLockb() {
    synchronized (this) {
      lockedByThis.field = new Object();
    }

    // accessing after the synchronized object
    // :: error: (lock.not.held)
    lockedByThis.field = new Object(); // error
  }

  synchronized void synchronizedMethodb() {
    lockedByThis.field = new Object();
  }

  void test() {
    // synchronized over the right object
    final Fields a = new Fields();
    final Fields b = new Fields();

    synchronized (this) {
      lockedByThis.field = new Object();
      // :: error: (lock.not.held)
      a.lockedByThis.field = new Object(); // error
      // :: error: (lock.not.held)
      b.lockedByThis.field = new Object(); // error
    }

    synchronized (a) {
      // :: error: (lock.not.held)
      lockedByThis.field = new Object(); // error
      a.lockedByThis.field = new Object();
      // :: error: (lock.not.held)
      b.lockedByThis.field = new Object(); // error
    }

    synchronized (b) {
      // :: error: (lock.not.held)
      lockedByThis.field = new Object(); // error
      // :: error: (lock.not.held)
      a.lockedByThis.field = new Object(); // error
      b.lockedByThis.field = new Object();
    }
  }
}