JVM value classes, interfaces, and defaults

test.java

// http://cr.openjdk.java.net/~jrose/values/values-0.html
//
// Can a value class implement interfaces? Yes. Boxing may occur when we treat a value as an interface instance.
//
// ...
//
// Since values do not have identity, there are certain operations that are
// identity-specific and either need to be disallowed on values or assigned a
// new meaning for use in the context of values.
// 
//  * Locking. Using a value as the lock object of a synchronized statement, 
//    or calling the related methods wait and notify, should be disallowed.
public class test {

  static interface Default {
  	default public void foo() {
  		synchronized(this) {
  			System.out.println("Default.foo");
  		}
  	}
  }

  static /*value*/ class Meter implements Default {
  	public Double value;
  }

  new Meter().foo()
}