Make factors serializable

src/ext/java/org/opentripplanner/ext/flex/FlexTripsMapper.java

@@ -35,9 +35,9 @@ public class FlexTripsMapper {
     for (Trip trip : stopTimesByTrip.keys()) {
       /* Fetch the stop times for this trip. Copy the list since it's immutable. */
       List<StopTime> stopTimes = new ArrayList<>(stopTimesByTrip.get(trip));
-      var factors = builder.getFlexDurationFactors().getOrDefault(trip, FlexDurationFactors.ZERO);
 
       if (UnscheduledTrip.isUnscheduledTrip(stopTimes)) {
+        var factors = builder.getFlexDurationFactors().getOrDefault(trip, FlexDurationFactors.ZERO);
         result.add(
           UnscheduledTrip
             .of(trip.getId())

src/ext/java/org/opentripplanner/ext/flex/trip/FlexDurationFactors.java

@@ -1,15 +1,21 @@
 package org.opentripplanner.ext.flex.trip;
 
+import java.io.Serializable;
 import java.time.Duration;
+import org.opentripplanner.framework.time.DurationUtils;
+import org.opentripplanner.framework.tostring.ToStringBuilder;
 
-public class FlexDurationFactors {
+public class FlexDurationFactors implements Serializable {
 
   public static FlexDurationFactors ZERO = new FlexDurationFactors(Duration.ZERO, 1);
   private final int offset;
   private final float factor;
 
   public FlexDurationFactors(Duration offset, float factor) {
-    this.offset = (int) offset.toSeconds();
+    if (factor < 0.1) {
+      throw new IllegalArgumentException("Flex duration factor must not be less than 0.1");
+    }
+    this.offset = (int) DurationUtils.requireNonNegative(offset).toSeconds();
     this.factor = factor;
   }
 
@@ -24,4 +30,13 @@ public int offsetInSeconds() {
   boolean nonZero() {
     return offset != 0 && factor != 1.0;
   }
+
+  @Override
+  public String toString() {
+    return ToStringBuilder
+      .of(FlexDurationFactors.class)
+      .addNum("factor", factor)
+      .addDurationSec("offset", offset)
+      .toString();
+  }
 }