Biased Locking in Java SE 6 - FreeOZ论坛

$ java LockingInJava2
java.runtime.version = 1.6.0_21-b06
java.vendor = Sun Microsystems Inc.
java.version = 1.6.0_21
os.name = Linux
os.version = 2.6.32-24-generic
lock creator = Thread-0
runnable[0]: thread name = Thread-0, counter=467
runnable[1]: thread name = Thread-1, counter=47
runnable[2]: thread name = Thread-2, counter=152
runnable[3]: thread name = Thread-3, counter=326
runnable[4]: thread name = Thread-4, counter=2

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$ java -XX:-UseBiasedLocking LockingInJava2
java.runtime.version = 1.6.0_21-b06
java.vendor = Sun Microsystems Inc.
java.version = 1.6.0_21
os.name = Linux
os.version = 2.6.32-24-generic
lock creator = Thread-0
runnable[0]: thread name = Thread-0, counter=250
runnable[1]: thread name = Thread-1, counter=60
runnable[2]: thread name = Thread-2, counter=71
runnable[3]: thread name = Thread-3, counter=99
runnable[4]: thread name = Thread-4, counter=514

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public class LockingInJava2 implements Runnable {
static int THREAD_COUNT = 5;
//static Object LOCK = new Object();
static Object LOCK = null;
static Runnable[] RUNNABLE_ARRAY = new Runnable[THREAD_COUNT];
static Thread[] THREAD_ARRAY = new Thread[THREAD_COUNT];
static String LOCK_CREATOR = null;
private int counter = 0;
private String threadId;
public static void main(String args[]) throws InterruptedException {
printEnvironmentInfo();
execute();
printResults();
}
/**
* Try to create a biased lock
*/
public synchronized static Object getLock() {
if(LOCK == null){
LOCK = new Object();
LOCK_CREATOR = Thread.currentThread().getName();
}
return LOCK;
}
public static void printEnvironmentInfo() {
System.out.println("java.runtime.version = "
+ System.getProperty("java.runtime.version"));
System.out.println("java.vendor = "
+ System.getProperty("java.vendor"));
System.out.println("java.version = "
+ System.getProperty("java.version"));
System.out.println("os.name = "
+ System.getProperty("os.name"));
System.out.println("os.version = "
+ System.getProperty("os.version"));
}
public static void execute() throws InterruptedException {
for (int i = 0; i < THREAD_COUNT; i++) {
RUNNABLE_ARRAY[i] = new LockingInJava2();
THREAD_ARRAY[i] = new Thread(RUNNABLE_ARRAY[i]);
}
for (Thread t : THREAD_ARRAY) {
t.start();
}
// let the threads run for a while
Thread.sleep(10000);
for (int i = THREAD_COUNT - 1; i >= 0; i--) {
THREAD_ARRAY[i].interrupt();
}
Thread.sleep(100); // wait a moment for termination, to lazy for join ;)
}
public static void printResults() {
System.out.println("lock creator = " + LOCK_CREATOR);
for (int i = 0; i < RUNNABLE_ARRAY.length; i++) {
System.out.println("runnable[" + i + "]: " + RUNNABLE_ARRAY[i]);
}
}
public void run() {
threadId = Thread.currentThread().getName();
Object myLock = getLock();
for (;;) {
synchronized (myLock) {
counter++;
try {
Thread.sleep(10);
} catch (InterruptedException ex) {
break;
}
}
}
}
public String toString() {
return "thread name = " + threadId + ", counter=" + counter;
}
}

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