fix: use double check to fix concurrent problem (iluwatar#1909)

npczwh · zhangwenhe · web-flow · commit 89b20721316f · 2021-11-11T19:46:24.000+02:00
Co-authored-by: zhangwenhe &lt;zhangwh@ehualu.com&gt;
diff --git a/leader-followers/src/main/java/com/iluwatar/leaderfollowers/Worker.java b/leader-followers/src/main/java/com/iluwatar/leaderfollowers/Worker.java
@@ -57,9 +57,11 @@ public void run() {
       try {
         if (workCenter.getLeader() != null && !workCenter.getLeader().equals(this)) {
           synchronized (workCenter) {
-            workCenter.wait();
+            if (workCenter.getLeader() != null && !workCenter.getLeader().equals(this)) {
+              workCenter.wait();
+              continue;
+            }
           }
-          continue;
         }
         final Task task = taskSet.getTask();
         synchronized (workCenter) {

Original file line number	Diff line number	Diff line change
`@@ -57,9 +57,11 @@ public void run() {`
`57`	`57`	`try {`
`58`	`58`	`if (workCenter.getLeader() != null && !workCenter.getLeader().equals(this)) {`
`59`	`59`	`synchronized (workCenter) {`
`60`		`- workCenter.wait();`
	`60`	`+ if (workCenter.getLeader() != null && !workCenter.getLeader().equals(this)) {`
	`61`	`+ workCenter.wait();`
	`62`	`+ continue;`
	`63`	`+ }`
`61`	`64`	`}`
`62`		`- continue;`
`63`	`65`	`}`
`64`	`66`	`final Task task = taskSet.getTask();`
`65`	`67`	`synchronized (workCenter) {`