Java Practices->Synchronized is implementation detail

Synchronized is implementation detail

Although the synchronized keyword can appear in a method header, it does not form a part of a method's API or contract. Synchronization is part of the implementation, not part of the interface.

Note: some early Sun documentation (javadoc) included the synchronized keyword in the description of methods. This error was corrected in Javadoc 1.2.

Example

Here, a concrete implementation of an interface uses synchronized for some methods, even though the interface methods themselves make no mention of it.

public interface ScientificTheory {
  
  void publish();
  
  void predict();
  
  boolean falsifyThroughMeasurement();
  
}

public final class LoopQuantumGravity implements ScientificTheory {

  @Override public synchronized void publish() {
    //..elided
  }
  
  @Override public synchronized void predict() {
    //..elided
  }
  
  @Override public boolean falsifyThroughMeasurement() {
    return true; //stub 
  }
  
}