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 class LoopQuantumGravity implements ScientificTheory {

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