Prefer immutable collections where possible

src/main/java/org/gaul/s3proxy/CrossOriginResourceSharing.java

@@ -18,6 +18,7 @@ package org.gaul.s3proxy;
 
 import java.util.Collection;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Objects;
 import java.util.Set;
 import java.util.regex.Matcher;
@@ -28,7 +29,6 @@ import com.google.common.base.Splitter;
 import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
-import com.google.common.collect.Lists;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -58,9 +58,9 @@ public final class CrossOriginResourceSharing {
 
     public CrossOriginResourceSharing() {
         // CORS Allow all
-        this(Lists.newArrayList(ALLOW_ANY_ORIGIN), SUPPORTED_METHODS,
+        this(List.of(ALLOW_ANY_ORIGIN), SUPPORTED_METHODS,
-            Lists.newArrayList(ALLOW_ANY_HEADER),
+            List.of(ALLOW_ANY_HEADER),
-            Lists.newArrayList(EXPOSE_ALL_HEADERS), "");
+            List.of(EXPOSE_ALL_HEADERS), "");
     }
 
     public CrossOriginResourceSharing(Collection<String> allowedOrigins,

src/main/java/org/gaul/s3proxy/S3Proxy.java

@@ -28,6 +28,7 @@ import java.util.Properties;
 import com.google.common.base.Joiner;
 import com.google.common.base.Splitter;
 import com.google.common.base.Strings;
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Lists;
 
 import org.eclipse.jetty.http.HttpCompliance;
@@ -291,10 +292,11 @@ public final class S3Proxy {
                 }
 
                 builder.corsRules(new CrossOriginResourceSharing(
-                        Lists.newArrayList(splitter.split(corsAllowOrigins)),
+                        ImmutableList.copyOf(splitter.split(corsAllowOrigins)),
-                        Lists.newArrayList(splitter.split(corsAllowMethods)),
+                        ImmutableList.copyOf(splitter.split(corsAllowMethods)),
-                        Lists.newArrayList(splitter.split(corsAllowHeaders)),
+                        ImmutableList.copyOf(splitter.split(corsAllowHeaders)),
-                        Lists.newArrayList(splitter.split(corsExposedHeaders)),
+                        ImmutableList.copyOf(splitter.split(
+                                corsExposedHeaders)),
                         allowCredentials));
             }
 

src/test/java/org/gaul/s3proxy/CrossOriginResourceSharingRuleTest.java

@@ -20,8 +20,6 @@ import static org.assertj.core.api.Assertions.assertThat;
 
 import java.util.List;
 
-import com.google.common.collect.Lists;
-
 import org.junit.Before;
 import org.junit.Test;
 
@@ -36,11 +34,11 @@ public final class CrossOriginResourceSharingRuleTest {
         corsAll = new CrossOriginResourceSharing();
         // CORS Configured
         corsCfg = new CrossOriginResourceSharing(
-                Lists.newArrayList("https://example\\.com",
+                List.of("https://example\\.com",
                         "https://.+\\.example\\.com",
                         "https://example\\.cloud"),
-                Lists.newArrayList("GET", "PUT"),
+                List.of("GET", "PUT"),
-                Lists.newArrayList("Accept", "Content-Type"),
+                List.of("Accept", "Content-Type"),
                 List.of(),
                 "true");
         // CORS disabled