Prefer Splitter over String.split

The latter has surprising semantics.  Found via error-prone 2.2.0.

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

@@ -35,6 +35,7 @@ import javax.crypto.spec.SecretKeySpec;
 import javax.servlet.http.HttpServletRequest;
 
 import com.google.common.base.Joiner;
+import com.google.common.base.Splitter;
 import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.SortedSetMultimap;
@@ -192,7 +193,7 @@ final class AwsSignature {
     }
 
     @Nullable
-    private static String[] extractSignedHeaders(String authorization) {
+    private static List<String> extractSignedHeaders(String authorization) {
         int index = authorization.indexOf("SignedHeaders=");
         if (index < 0) {
             return null;
@@ -202,11 +203,12 @@ final class AwsSignature {
             return null;
         }
         int startHeaders = authorization.indexOf('=', index);
-        return authorization.substring(startHeaders + 1, endSigned).split(";");
+        return Splitter.on(';').splitToList(authorization.substring(
+                startHeaders + 1, endSigned));
     }
 
     private static String buildCanonicalHeaders(HttpServletRequest request,
-                                                String[] signedHeaders) {
+            List<String> signedHeaders) {
         List<String> headers = new ArrayList<>();
         for (String header : signedHeaders) {
             headers.add(header.toLowerCase());
@@ -271,12 +273,12 @@ final class AwsSignature {
         } else {
             digest = getMessageDigest(payload, hashAlgorithm);
         }
-        String[] signedHeaders;
+        List<String> signedHeaders;
         if (authorizationHeader != null) {
             signedHeaders = extractSignedHeaders(authorizationHeader);
         } else {
-            signedHeaders = request.getParameter("X-Amz-SignedHeaders")
-                    .split(";");
+            signedHeaders = Splitter.on(';').splitToList(request.getParameter(
+                    "X-Amz-SignedHeaders"));
         }
         String canonicalRequest = Joiner.on("\n").join(
                 request.getMethod(),

src/main/java/org/gaul/s3proxy/S3AuthorizationHeader.java

@@ -16,6 +16,9 @@
 
 package org.gaul.s3proxy;
 
+import java.util.List;
+
+import com.google.common.base.Splitter;
 import com.google.common.collect.ImmutableMap;
 
 final class S3AuthorizationHeader {
@@ -48,16 +51,17 @@ final class S3AuthorizationHeader {
             region = null;
             date = null;
             service = null;
-            String[] fields = header.split(" ");
-            if (fields.length != 2) {
+            List<String> fields = Splitter.on(' ').splitToList(header);
+            if (fields.size() != 2) {
                 throw new IllegalArgumentException("Invalid header");
             }
-            String[] identityTuple = fields[1].split(":");
-            if (identityTuple.length != 2) {
+            List<String> identityTuple = Splitter.on(':').splitToList(
+                    fields.get(1));
+            if (identityTuple.size() != 2) {
                 throw new IllegalArgumentException("Invalid header");
             }
-            identity = identityTuple[0];
-            signature = identityTuple[1];
+            identity = identityTuple.get(0);
+            signature = identityTuple.get(1);
         } else if (header.startsWith("AWS4-HMAC")) {
             authenticationType = AuthenticationType.AWS_V4;
             signature = extractSignature(header);
@@ -72,19 +76,21 @@ final class S3AuthorizationHeader {
             }
             String credential = header.substring(credentialIndex +
                     CREDENTIAL_FIELD.length(), credentialEnd);
-            String[] fields = credential.split("/");
-            if (fields.length != 5) {
+            List<String> fields = Splitter.on('/').splitToList(credential);
+            if (fields.size() != 5) {
                 throw new IllegalArgumentException(
                         "Invalid Credential: " + credential);
             }
-            identity = fields[0];
-            date = fields[1];
-            region = fields[2];
-            service = fields[3];
+            identity = fields.get(0);
+            date = fields.get(1);
+            region = fields.get(2);
+            service = fields.get(3);
             String awsSignatureVersion = header.substring(
                     0, header.indexOf(' '));
-            hashAlgorithm = DIGEST_MAP.get(awsSignatureVersion.split("-")[2]);
-            hmacAlgorithm = "Hmac" + awsSignatureVersion.split("-")[2];
+            hashAlgorithm = DIGEST_MAP.get(Splitter.on('-').splitToList(
+                    awsSignatureVersion).get(2));
+            hmacAlgorithm = "Hmac" + Splitter.on('-').splitToList(
+                    awsSignatureVersion).get(2);
         } else {
             throw new IllegalArgumentException("Invalid header");
         }

src/main/java/org/gaul/s3proxy/S3ProxyHandler.java

@@ -59,6 +59,7 @@ import javax.xml.stream.XMLStreamWriter;
 import com.fasterxml.jackson.dataformat.xml.XmlMapper;
 import com.google.common.base.CharMatcher;
 import com.google.common.base.Optional;
+import com.google.common.base.Splitter;
 import com.google.common.base.Strings;
 import com.google.common.cache.Cache;
 import com.google.common.cache.CacheBuilder;
@@ -2779,8 +2780,8 @@ public class S3ProxyHandler {
     }
 
     private static boolean validateIpAddress(String string) {
-        String[] parts = string.split("\\.");
-        if (parts.length != 4) {
+        List<String> parts = Splitter.on('.').splitToList(string);
+        if (parts.size() != 4) {
             return false;
         }
         for (String part : parts) {