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Created by alfa on June 07, 2011 11:34:26    Last update: June 07, 2011 11:36:37
This is an example that uses dynamic proxies to trace method calls (in logging) and print out elapsed times for them. Because dynamic proxies can only be generated for interfaces, the service classes must be implemented with interface-implementation pairs. Create services A and B. A.java : public interface A { public void service1()... AImpl.java : import java.util.Random; public class AImpl... B.java : public interface B { public void service1()... BImpl.java : public class BImpl implements B { public vo... The call trace proxy: import java.lang.reflect.*; class TraceProx... The performance proxy: import java.lang.reflect.*; class Performan... The service factory: import java.lang.reflect.*; public class Se... The test class: public class Test { public static void main... The output: Entering AImpl.service1 Entering BImpl.service1... The above example has no information...
Created by alfa on June 02, 2011 15:26:37    Last update: June 02, 2011 15:26:37
While doing some Java reflection code, I noticed the method Class.isSynthetic() , which the JavaDoc says returns " true if and only if this class is a synthetic class as defined by the Java Language Specification". However, there's no definition of "synthetic class" in the JLS ! The only thing that I can find that remotely resembles a definition is in the JVM spec , where it defines the synthetic attribute : "The Synthetic attribute is a fixed-length attribute in the attributes table of ClassFile (§4.1), field_info (§4.5), and method_info (§4.6) structures. A class member that does not appear in the source code must be marked using a Synthetic attribute." By this definition, a default constructor, which does not appear in the source code, should...
Created by Dr. Xi on April 27, 2011 15:58:31    Last update: April 27, 2011 20:05:22
From JavaDoc : java.util.concurrent.locks.ReentrantLock is a reentrant mutual exclusion Lock with the same basic behavior and semantics as the implicit monitor lock accessed using synchronized methods and statements, but with extended capabilities. The extended capabilities are: tryLock() : acquire the lock if possible, otherwise immediately return false. tryLock(long timeout, TimeUnit unit) : acquire the lock within the timeout, return false after timeout. lockInterruptibly() : try to acquire the lock and enter wait state, but can be interrupted by other threads and exit waiting. The following shows how java.util.concurrent.locks.ReentrantLock can be used. Start two threads to manipulate the same counter, one incrementing, the other decrementing. Since the counter is incremented and decremented the same number of times, in the end, it should be 0. Without locking,...