Fix spotbugs warnings.

ttnhabbridge/src/main/java/nl/sikken/bertrik/hab/ExpiringCache.java

@@ -19,7 +19,7 @@ public final class ExpiringCache {
      * @param expiryTime the expiry time
      */
     public ExpiringCache(Duration expiryTime) {
-        this.expiryTime = expiryTime;
+        this.expiryTime = Duration.from(expiryTime);
     }
     
     /**
@@ -42,11 +42,7 @@ public final class ExpiringCache {
      */
     private void cleanUp(Instant now) {
         Instant limit = now.minus(expiryTime);
-        map.forEach((k,v) -> {
-            if (v.isBefore(limit)) {
-                map.remove(k, v);
-            }
-        });
+        map.values().removeIf(v -> v.isBefore(limit));
     }
     
 }

ttnhabbridge/src/main/java/nl/sikken/bertrik/hab/Sentence.java

@@ -1,6 +1,7 @@
 package nl.sikken.bertrik.hab;
 
 import java.nio.charset.StandardCharsets;
+import java.time.Duration;
 import java.time.Instant;
 import java.time.LocalDateTime;
 import java.time.ZoneId;
@@ -34,7 +35,7 @@ public final class Sentence {
     public Sentence(String callSign, int id, Instant time) {
         this.callSign = callSign;
         this.id = id;
-        this.time = time;
+        this.time = Instant.from(time);
     }
 
     /**

ttnhabbridge/src/main/java/nl/sikken/bertrik/hab/habitat/UuidsList.java

@@ -2,6 +2,7 @@ package nl.sikken.bertrik.hab.habitat;
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
@@ -29,7 +30,7 @@ public final class UuidsList {
     }
 
     public List<String> getUuids() {
-        return uuids;
+        return Collections.unmodifiableList(uuids);
     }
     
 }

ttnhabbridge/src/main/java/nl/sikken/bertrik/hab/ttn/TtnUplinkMessage.java

@@ -2,6 +2,7 @@ package nl.sikken.bertrik.hab.ttn;
 
 import java.time.Instant;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -26,7 +27,7 @@ public final class TtnUplinkMessage {
 
     public TtnUplinkMessage(Instant time, String appId, String deviceId, int counter, int port, byte[] payloadRaw,
             boolean isRetry) {
-        this.time = time;
+        this.time = Instant.from(time);
         this.appId = appId;
         this.deviceId = deviceId;
         this.counter = counter;
@@ -40,7 +41,7 @@ public final class TtnUplinkMessage {
     }
 
     public Instant getTime() {
-        return time;
+        return Instant.from(time);
     }
 
     public String getAppId() {
@@ -76,7 +77,7 @@ public final class TtnUplinkMessage {
     }
 
     public List<GatewayInfo> getGateways() {
-        return gateways;
+        return Collections.unmodifiableList(gateways);
     }
 
     public static final class GatewayInfo {