Added Elevator Algorithm in Java

chris-len · web-flow · commit f3100f578da4 · 2017-10-11T13:12:06.000+02:00
diff --git a/ElevatorAlgorithm/Java/ElevatorAlgorithm.java b/ElevatorAlgorithm/Java/ElevatorAlgorithm.java
@@ -0,0 +1,61 @@
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+public class ElevatorAlgorithm {
+
+    static void startCSCAN(int pos, List<Integer> disk_requests)
+    {
+        System.out.println("Using C-SCAN algorithm on pending dist requests: " + disk_requests);
+        System.out.println("Starting position is: " + pos + "\n");
+
+        if (disk_requests.size() == 0)
+        {
+            System.out.println("Nothing to do.");
+        }
+
+        Collections.sort(disk_requests);
+
+        int next_array_pos = disk_requests.stream()
+                .map(disk_requests::indexOf)
+                .filter(x -> disk_requests.get(x) > pos)
+                .findFirst().orElse(0);
+
+        int curr_position = pos;
+        int seek_number = 1;
+        int motion_sum = 0;
+
+        for (int i = 0; i < disk_requests.size(); i++)
+        {
+            if (next_array_pos == 0 && curr_position != 0)
+            {
+                curr_position = 0;
+                System.out.println("Seek " + seek_number + ": returning head to track 0, motion: 0");
+                seek_number++;
+            }
+
+            int next_position = disk_requests.get(next_array_pos);
+            int motion = Math.abs(curr_position-next_position);
+            System.out.println("Seek " + seek_number + ": " + next_position + "-" + curr_position + " motion: " + motion);
+
+            seek_number++;
+            motion_sum += motion;
+
+            curr_position = next_position;
+            next_array_pos = (next_array_pos+1)%disk_requests.size();
+        }
+
+        System.out.println("\nTotal motion C-SCAN: " + motion_sum);
+    }
+
+    public static void main(String... arg)
+    {
+        int pos = 35;
+
+        List<Integer> disk_request_list = Arrays.asList(100, 50, 10, 20, 75);
+
+        startCSCAN(pos, disk_request_list);
+    }
+
+
+}
