Listing 1. VMs have cheap synchronization for unlocked objects, but the cost may be worse than you expect because threading issues interfere with other taken-for-granted optimizations.

/**
   * Illustrates overhead of method 
   * synchronization.
   */
class Test1
{
   private int a, b, c;
   
   /**
   * Setter for a single attribute.
   */
   public synchronized void setA (int a)
   {
      this.a = a;
   }
   
   /**
   * Setter for multiple attributes.
   */
   public synchronized void f (int b, int c)
   {
      this.b = b;
      this.c = c;
   }
   
   public static void main(String[] args)
   {
      Test1 test1 = new Test1();
      test1.setA(10);
      test1.f(20, 30);
   }
}