你要锁什么？thread里面的同步关键字锁的是线程本身，当然没用

另外你start之后立即打印能有什么效果。。

public class TestCallable {
public static int a = 0;
public static AtomicInteger c = new AtomicInteger(0);
public static void main(String[] args) throws InterruptedException {
iThread t1 = new iThread();
iThread t2 = new iThread();
t1.start();
t2.start();
Thread.sleep(2000);
try {
System.out.println("atomic c: " + c);
System.out.println("int a : " + a);
} catch (Exception e) {
e.printStackTrace();
}
}
}
class iThread extends Thread {
private static final Object LOCK = new Object();
@Override
public void run() {
for (int i = 0; i < 1000; i++) {
synchronized (LOCK) {
TestCallable.a++;
}
TestCallable.c.incrementAndGet();
}
}
}