Solution includes below changes :

.gitignore

@@ -0,0 +1,2 @@
+/out
+/.idea

Java/src/main/java/com/tollcalculator/constants/TollCalculatorConstants.java

@@ -0,0 +1,12 @@
+package com.tollcalculator.constants;
+
+public class TollCalculatorConstants {
+    public static final int MAX_FEE=60;
+    public static final String MOTORBIKE="Motorbike";
+    public static final String DIPLOMAT="Diplomat";
+    public static final String EMERGENCY="Emergency";
+    public static final String MILITARY="Military";
+    public static final String TRACTOR="Tractor";
+    public static final String FOREIGN="Foreign";
+    public static final String CAR="Car";
+}

Java/src/main/java/com/tollcalculator/enums/TollFreeVehicles.java

@@ -0,0 +1,21 @@
+package com.tollcalculator.enums;
+
+import com.tollcalculator.constants.TollCalculatorConstants;
+
+public enum TollFreeVehicles {
+    MOTORBIKE(TollCalculatorConstants.MOTORBIKE),
+    TRACTOR(TollCalculatorConstants.TRACTOR),
+    EMERGENCY(TollCalculatorConstants.EMERGENCY),
+    DIPLOMAT(TollCalculatorConstants.DIPLOMAT),
+    FOREIGN(TollCalculatorConstants.FOREIGN),
+    MILITARY(TollCalculatorConstants.MILITARY);
+    private final String type;
+
+    TollFreeVehicles(String type) {
+        this.type = type;
+    }
+
+    public String getType() {
+        return type;
+    }
+}

Java/src/main/java/com/tollcalculator/pojo/Car.java

@@ -0,0 +1,10 @@
+package com.tollcalculator.pojo;
+
+import com.tollcalculator.constants.TollCalculatorConstants;
+
+public class Car implements Vehicle {
+  @Override
+  public String getType() {
+    return TollCalculatorConstants.CAR;
+  }
+}

Java/src/main/java/com/tollcalculator/pojo/Diplomat.java

@@ -0,0 +1,10 @@
+package com.tollcalculator.pojo;
+
+import com.tollcalculator.constants.TollCalculatorConstants;
+
+public class Diplomat implements Vehicle{
+    @Override
+    public String getType() {
+        return TollCalculatorConstants.DIPLOMAT;
+    }
+}

Java/src/main/java/com/tollcalculator/pojo/Emergency.java

@@ -0,0 +1,10 @@
+package com.tollcalculator.pojo;
+
+import com.tollcalculator.constants.TollCalculatorConstants;
+
+public class Emergency implements Vehicle{
+    @Override
+    public String getType() {
+        return TollCalculatorConstants.EMERGENCY;
+    }
+}

Java/src/main/java/com/tollcalculator/pojo/Foreign.java

@@ -0,0 +1,10 @@
+package com.tollcalculator.pojo;
+
+import com.tollcalculator.constants.TollCalculatorConstants;
+
+public class Foreign implements Vehicle{
+    @Override
+    public String getType() {
+        return TollCalculatorConstants.FOREIGN;
+    }
+}

Java/src/main/java/com/tollcalculator/pojo/Military.java

@@ -0,0 +1,10 @@
+package com.tollcalculator.pojo;
+
+import com.tollcalculator.constants.TollCalculatorConstants;
+
+public class Military implements Vehicle{
+    @Override
+    public String getType() {
+        return TollCalculatorConstants.MILITARY;
+    }
+}

Java/src/main/java/com/tollcalculator/pojo/Motorbike.java

@@ -0,0 +1,10 @@
+package com.tollcalculator.pojo;
+
+import com.tollcalculator.constants.TollCalculatorConstants;
+
+public class Motorbike implements Vehicle {
+  @Override
+  public String getType() {
+    return TollCalculatorConstants.MOTORBIKE;
+  }
+}

Java/src/main/java/com/tollcalculator/pojo/Tractor.java

@@ -0,0 +1,11 @@
+package com.tollcalculator.pojo;
+
+import com.tollcalculator.constants.TollCalculatorConstants;
+
+public class Tractor implements Vehicle{
+
+    @Override
+    public String getType() {
+        return TollCalculatorConstants.TRACTOR;
+    }
+}

Java/Vehicle.java → Java/src/main/java/com/tollcalculator/pojo/Vehicle.java

@@ -1,3 +1,4 @@
+package com.tollcalculator.pojo;
 
 public interface Vehicle {
 

Java/TollCalculator.java → Java/src/main/java/com/tollcalculator/service/TollCalculator.java

@@ -1,7 +1,14 @@
+package com.tollcalculator.service;
+
+import com.tollcalculator.constants.TollCalculatorConstants;
+import com.tollcalculator.enums.TollFreeVehicles;
+import com.tollcalculator.pojo.Vehicle;
 
 import java.util.*;
 import java.util.concurrent.*;
 
+import static com.tollcalculator.constants.TollCalculatorConstants.MAX_FEE;
+
 public class TollCalculator {
 
   /**
@@ -12,26 +19,39 @@ public class TollCalculator {
    * @return - the total toll fee for that day
    */
   public int getTollFee(Vehicle vehicle, Date... dates) {
-    Date intervalStart = dates[0];
-    int totalFee = 0;
-    for (Date date : dates) {
-      int nextFee = getTollFee(date, vehicle);
-      int tempFee = getTollFee(intervalStart, vehicle);
-
-      TimeUnit timeUnit = TimeUnit.MINUTES;
-      long diffInMillies = date.getTime() - intervalStart.getTime();
-      long minutes = timeUnit.convert(diffInMillies, TimeUnit.MILLISECONDS);
-
-      if (minutes <= 60) {
-        if (totalFee > 0) totalFee -= tempFee;
-        if (nextFee >= tempFee) tempFee = nextFee;
-        totalFee += tempFee;
-      } else {
-        totalFee += nextFee;
+
+    if(null!=dates && null!=vehicle){
+      Arrays.sort(dates);
+      Date intervalStart = dates[0];
+      int totalFee = 0;
+      for (Date date : dates) {
+        /**
+         * Maximum total fee is 60 .So if the total fee is greater than 60 then no need to calculate further
+         */
+        if (totalFee > MAX_FEE) {
+          totalFee = MAX_FEE;
+          return totalFee;
+        }
+        int nextFee = getTollFee(date, vehicle);
+        int tempFee = getTollFee(intervalStart, vehicle);
+
+        TimeUnit timeUnit = TimeUnit.MINUTES;
+        long diffInMillies = date.getTime() - intervalStart.getTime();
+        long minutes = timeUnit.convert(diffInMillies, TimeUnit.MILLISECONDS);
+
+        if (minutes <= 60) {
+          if (totalFee > 0) totalFee -= tempFee;
+          if (nextFee >= tempFee) tempFee = nextFee;
+          totalFee += tempFee;
+        } else {
+          totalFee += nextFee;
+          intervalStart = date;
+        }
       }
+      return totalFee;
+    }else{
+      throw new RuntimeException("Vehicle or Dates should not be null");
     }
-    if (totalFee > 60) totalFee = 60;
-    return totalFee;
   }
 
   private boolean isTollFreeVehicle(Vehicle vehicle) {
@@ -89,22 +109,5 @@ private Boolean isTollFreeDate(Date date) {
     return false;
   }
 
-  private enum TollFreeVehicles {
-    MOTORBIKE("Motorbike"),
-    TRACTOR("Tractor"),
-    EMERGENCY("Emergency"),
-    DIPLOMAT("Diplomat"),
-    FOREIGN("Foreign"),
-    MILITARY("Military");
-    private final String type;
-
-    TollFreeVehicles(String type) {
-      this.type = type;
-    }
-
-    public String getType() {
-      return type;
-    }
-  }
 }