我们首先开发一个BusyFlag的类，类似于C++中的Simaphore。
- public class BusyFlag {
- protected Thread busyflag = null;
- protected int busycount = 0;
-
- public synchronized void getBusyFlag() {
- while (tryGetBusyFlag() == false) {
- try {
- wait();
- } catch (Exception e) {}
- }
- }
-
- private synchronized boolean tryGetBusyFlag() {
- if (busyflag == null) {
- busyflag = Thread.currentThread();
- busycount = 1;
- return true;
- }
-
- if (busyflag == Thread.currentThread()) {
- busycount++;
- return true;
- }
- return false;
- }
-
- public synchronized void freeBusyFlag() {
- if(getOwner()== Thread.currentThread()) {
- busycount--;
- if(busycount==0) {
- busyflag = null;
- notify();
- }
- }
- }
-
- public synchronized Thread getOwner() {
- return busyflag;
- }
- }
