QPID-8653: [Broker-J] Code cleanup: collection type arguments, collection factory methods, lambdas (#199)

diff --git a/systests/end-to-end-conversion-tests/src/main/java/org/apache/qpid/systests/end_to_end_conversion/client/AugumentConnectionUrl.java b/systests/end-to-end-conversion-tests/src/main/java/org/apache/qpid/systests/end_to_end_conversion/client/AugumentConnectionUrl.java
index 44dade9..d2fe2fe 100644
--- a/systests/end-to-end-conversion-tests/src/main/java/org/apache/qpid/systests/end_to_end_conversion/client/AugumentConnectionUrl.java
+++ b/systests/end-to-end-conversion-tests/src/main/java/org/apache/qpid/systests/end_to_end_conversion/client/AugumentConnectionUrl.java
@@ -20,7 +20,6 @@
 
 package org.apache.qpid.systests.end_to_end_conversion.client;
 
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -37,6 +36,6 @@
 
     public Map<String, String> getConnectionUrlConfig()
     {
-        return Collections.unmodifiableMap(_connectionUrlConfig);
+        return Map.copyOf(_connectionUrlConfig);
     }
 }
diff --git a/systests/end-to-end-conversion-tests/src/main/java/org/apache/qpid/systests/end_to_end_conversion/dependency_resolution/ClasspathQuery.java b/systests/end-to-end-conversion-tests/src/main/java/org/apache/qpid/systests/end_to_end_conversion/dependency_resolution/ClasspathQuery.java
index 8b62a99..00f1266 100644
--- a/systests/end-to-end-conversion-tests/src/main/java/org/apache/qpid/systests/end_to_end_conversion/dependency_resolution/ClasspathQuery.java
+++ b/systests/end-to-end-conversion-tests/src/main/java/org/apache/qpid/systests/end_to_end_conversion/dependency_resolution/ClasspathQuery.java
@@ -26,7 +26,6 @@
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -61,10 +60,10 @@
         _classpathCache = CacheBuilder.newBuilder()
                                       .maximumSize(8)
                                       .recordStats()
-                                      .build(new CacheLoader<Collection<String>, List<File>>()
+                                      .build(new CacheLoader<>()
                                       {
                                           @Override
-                                          public List<File> load(final Collection<String> key) throws Exception
+                                          public List<File> load(final Collection<String> key)
                                           {
                                               return doBuildClassPath(key);
                                           }
@@ -88,7 +87,7 @@
 
     private static List<File> doBuildClassPath(final Collection<String> gavs)
     {
-        return Collections.unmodifiableList(new ArrayList<>(getJarFiles(gavs)));
+        return List.copyOf(new ArrayList<>(getJarFiles(gavs)));
     }
 
     private static Set<File> getJarFiles(final Collection<String> gavs)
diff --git a/systests/end-to-end-conversion-tests/src/test/java/org/apache/qpid/systests/end_to_end_conversion/SimpleConversionTest.java b/systests/end-to-end-conversion-tests/src/test/java/org/apache/qpid/systests/end_to_end_conversion/SimpleConversionTest.java
index 43a2039..605367b 100644
--- a/systests/end-to-end-conversion-tests/src/test/java/org/apache/qpid/systests/end_to_end_conversion/SimpleConversionTest.java
+++ b/systests/end-to-end-conversion-tests/src/test/java/org/apache/qpid/systests/end_to_end_conversion/SimpleConversionTest.java
@@ -28,8 +28,6 @@
 import static org.junit.jupiter.api.Assumptions.assumeFalse;
 import static org.junit.jupiter.api.Assumptions.assumeTrue;
 
-import java.util.Arrays;
-import java.util.Collections;
 import java.util.EnumSet;
 import java.util.HashMap;
 import java.util.List;
@@ -157,8 +155,7 @@
     {
         final MessageDescription messageDescription = new MessageDescription();
         messageDescription.setMessageType(MessageDescription.MessageType.OBJECT_MESSAGE);
-        messageDescription.setContent(new SerializableTestClass(Collections.singletonMap("testKey", "testValue"),
-                                                                Collections.singletonList(42)));
+        messageDescription.setContent(new SerializableTestClass(Map.of("testKey", "testValue"), List.of(42)));
 
         performSimpleTest(messageDescription);
     }
@@ -199,7 +196,7 @@
         assumeTrue(AMQP_PRE010_PROTOCOLS.contains(getPublisherProtocolVersion()) &&
                 EnumSet.of(Protocol.AMQP_0_10).contains(getSubscriberProtocolVersion()));
 
-        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Collections.emptyMap());
+        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Map.of());
 
         ClientMessage publishedMessage = clientResults.get(0);
         ClientMessage subscriberMessage = clientResults.get(1);
@@ -214,7 +211,7 @@
         assumeTrue(AMQP_PRE010_PROTOCOLS.contains(getPublisherProtocolVersion()) &&
                 EnumSet.of(Protocol.AMQP_1_0).contains(getSubscriberProtocolVersion()));
 
-        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Collections.emptyMap());
+        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Map.of());
 
         ClientMessage publishedMessage = clientResults.get(0);
         ClientMessage subscriberMessage = clientResults.get(1);
@@ -232,7 +229,7 @@
         assumeTrue(EnumSet.of(Protocol.AMQP_0_10).contains(getPublisherProtocolVersion()) &&
                 AMQP_PRE010_PROTOCOLS.contains(getSubscriberProtocolVersion()));
 
-        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Collections.emptyMap());
+        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Map.of());
 
         ClientMessage publishedMessage = clientResults.get(0);
         ClientMessage subscriberMessage = clientResults.get(1);
@@ -248,7 +245,7 @@
         assumeTrue(EnumSet.of(Protocol.AMQP_0_10).contains(getPublisherProtocolVersion()) &&
                 EnumSet.of(Protocol.AMQP_1_0).contains(getSubscriberProtocolVersion()));
 
-        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Collections.emptyMap());
+        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Map.of());
 
         ClientMessage publishedMessage = clientResults.get(0);
         ClientMessage subscriberMessage = clientResults.get(1);
@@ -268,7 +265,7 @@
         assumeTrue(EnumSet.of(Protocol.AMQP_1_0).contains(getPublisherProtocolVersion()) &&
                 AMQP_PRE010_PROTOCOLS.contains(getSubscriberProtocolVersion()));
 
-        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Collections.emptyMap());
+        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Map.of());
 
         // On the wire the "message-id-string comprises an identity of the publisher + a message sequence number
         ClientMessage publishedMessage = clientResults.get(0);
@@ -283,7 +280,7 @@
         assumeTrue(EnumSet.of(Protocol.AMQP_1_0).contains(getPublisherProtocolVersion()) &&
                 AMQP_PRE010_PROTOCOLS.contains(getSubscriberProtocolVersion()));
 
-        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Collections.singletonMap(
+        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Map.of(
                 JMS_MESSAGE_IDPOLICY_MESSAGE_IDTYPE, "UUID"));
 
         ClientMessage publishedMessage = clientResults.get(0);
@@ -303,7 +300,7 @@
         assumeTrue(EnumSet.of(Protocol.AMQP_1_0).contains(getPublisherProtocolVersion()) &&
                 AMQP_PRE010_PROTOCOLS.contains(getSubscriberProtocolVersion()));
 
-        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Collections.singletonMap(
+        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Map.of(
                 JMS_MESSAGE_IDPOLICY_MESSAGE_IDTYPE, "UUID_STRING"));
 
         ClientMessage publishedMessage = clientResults.get(0);
@@ -324,7 +321,7 @@
         assumeTrue(EnumSet.of(Protocol.AMQP_1_0).contains(getPublisherProtocolVersion()) &&
                 AMQP_PRE010_PROTOCOLS.contains(getSubscriberProtocolVersion()));
 
-        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Collections.singletonMap(
+        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Map.of(
                 JMS_MESSAGE_IDPOLICY_MESSAGE_IDTYPE, "PREFIXED_UUID_STRING"));
 
         ClientMessage publishedMessage = clientResults.get(0);
@@ -344,7 +341,7 @@
         assumeTrue(EnumSet.of(Protocol.AMQP_1_0).contains(getPublisherProtocolVersion()) &&
                 EnumSet.of(Protocol.AMQP_0_10).contains(getSubscriberProtocolVersion()));
 
-        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Collections.emptyMap());
+        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Map.of());
 
         // On the wire the message-id is a message-id-string comprising an identity of the pubisher + a message
         // sequence number
@@ -361,7 +358,7 @@
         assumeTrue(EnumSet.of(Protocol.AMQP_1_0).contains(getPublisherProtocolVersion()) &&
                 EnumSet.of(Protocol.AMQP_0_10).contains(getSubscriberProtocolVersion()));
 
-        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Collections.singletonMap(
+        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Map.of(
                 JMS_MESSAGE_IDPOLICY_MESSAGE_IDTYPE, "UUID"));
 
         ClientMessage publishedMessage = clientResults.get(0);
@@ -381,7 +378,7 @@
         assumeTrue(EnumSet.of(Protocol.AMQP_1_0).contains(getPublisherProtocolVersion()) &&
                 EnumSet.of(Protocol.AMQP_0_10).contains(getSubscriberProtocolVersion()));
 
-        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Collections.singletonMap(
+        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Map.of(
                 JMS_MESSAGE_IDPOLICY_MESSAGE_IDTYPE, "UUID_STRING"));
 
         ClientMessage publishedMessage = clientResults.get(0);
@@ -401,7 +398,7 @@
         assumeTrue(EnumSet.of(Protocol.AMQP_1_0).contains(getPublisherProtocolVersion()) &&
                 EnumSet.of(Protocol.AMQP_0_10).contains(getSubscriberProtocolVersion()));
 
-        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Collections.singletonMap(
+        List<ClientMessage> clientResults = performProviderAssignedMessageIdTest(Map.of(
                 JMS_MESSAGE_IDPOLICY_MESSAGE_IDTYPE, "PREFIXED_UUID_STRING"));
 
         ClientMessage publishedMessage = clientResults.get(0);
@@ -587,17 +584,17 @@
                 new ClientInstructionBuilder().configureDestinations(_defaultDestinations)
                                               .receiveMessage(destinationJndiName, messageDescription)
                                               .build();
-        List<ClientResult> clientResults = performTest(publisherInstructions, subscriberInstructions);
+        final List<ClientResult> clientResults = performTest(publisherInstructions, subscriberInstructions);
         assertThat("Unexpected number of client results", clientResults.size(), equalTo(2));
 
-        ClientResult publishedClientResult = clientResults.get(0);
+        final ClientResult publishedClientResult = clientResults.get(0);
         assertThat("Unexpected number of published client messages", publishedClientResult.getClientMessages().size(), equalTo(1));
-        ClientMessage publishedMessage = publishedClientResult.getClientMessages().get(0);
+        final ClientMessage publishedMessage = publishedClientResult.getClientMessages().get(0);
 
-        ClientResult subscriberClientResults = clientResults.get(1);
+        final ClientResult subscriberClientResults = clientResults.get(1);
         assertThat("Unexpected number of published client messages", subscriberClientResults.getClientMessages().size(), equalTo(1));
-        ClientMessage subscriberMessage = subscriberClientResults.getClientMessages().get(0);
+        final ClientMessage subscriberMessage = subscriberClientResults.getClientMessages().get(0);
 
-        return Arrays.asList(publishedMessage, subscriberMessage);
+        return List.of(publishedMessage, subscriberMessage);
     }
 }