Create Traffic Light Controlled Intersection.java

Author: varunu28

Concurrency/Traffic Light Controlled Intersection.java

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+class TrafficLight {
+
+  private boolean greenOnRoadA;
+  private ReentrantLock lock;
+  
+  public TrafficLight() {
+    this.greenOnRoadA = true;
+    this.lock = new ReentrantLock();
+  }
+
+  public void carArrived(
+      int carId,           // ID of the car
+      int roadId,          // ID of the road the car travels on. Can be 1 (road A) or 2 (road B)
+      int direction,       // Direction of the car
+      Runnable turnGreen,  // Use turnGreen.run() to turn light to green on current road
+      Runnable crossCar    // Use crossCar.run() to make car cross the intersection 
+  ) {
+    this.lock.lock();
+    if(greenOnRoadA && roadId==2 || !greenOnRoadA && roadId==1){
+      greenOnRoadA = !greenOnRoadA;
+      turnGreen.run();
+    }
+    crossCar.run();
+    this.lock.unlock();     
+  }
+}