build(style): Add Checkstyle plugin for Gradle

.checkstyle/java.header

@@ -0,0 +1,4 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */

.checkstyle/suppressions.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0"?>
+
+<!--
+  ~ Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License").
+  ~ You may not use this file except in compliance with the License.
+  ~ A copy of the License is located at
+  ~
+  ~  http://aws.amazon.com/apache2.0
+  ~
+  ~ or in the "license" file accompanying this file. This file is distributed
+  ~ on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+  ~ express or implied. See the License for the specific language governing
+  ~ permissions and limitations under the License.
+  -->
+
+<!DOCTYPE suppressions PUBLIC
+        "-//Puppy Crawl//DTD Suppressions 1.2//EN"
+        "http://www.puppycrawl.com/dtds/suppressions_1_2.dtd">
+<suppressions>
+    <!-- ignore all checks for test classes except for the Header -->
+    <suppress checks="^((?!Header).)*$"
+              files=".*[\\/](test|integrationTest)[\\/]java[\\/].+\.java$"/>
+
+    <suppress checks="HideUtilityClassConstructor"
+              files=".*[\\/](examples)[\\/]java[\\/].+\.java$"/>
+
+</suppressions>

build.gradle

@@ -14,6 +14,7 @@ plugins {
     id 'jacoco'
     id 'jvm-test-suite'
     id 'jacoco-report-aggregation'
+    id 'checkstyle'
     id 'com.github.johnrengelman.shadow' version '7.1.2'
     id 'com.palantir.revapi' version '1.7.0'
 }
@@ -64,6 +65,7 @@ dependencies {
     implementation 'com.github.ben-manes.caffeine:caffeine:3.1.8'
 
     examplesImplementation project
+    examplesImplementation 'org.slf4j:slf4j-api:2.0.9'
 }
 
 publishing {
@@ -165,3 +167,8 @@ jacocoTestReport {
         xml.outputLocation = file("build/reports/coverage.xml")
     }
 }
+
+checkstyle {
+    toolVersion = '10.12.5'
+    configDirectory.set(new File(projectDir, ".checkstyle"))
+}

src/examples/java/software/amazon/nio/spi/examples/CopyToS3.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 package software.amazon.nio.spi.examples;
 
 import java.io.FileWriter;
@@ -10,6 +15,7 @@
 public class CopyToS3 {
     /**
      * Demonstrates a cross filesystem operation by copying a local (temp) file into an S3 bucket.
+     *
      * @param args the s3 path (URI) to copy to
      * @throws IOException if the temp file cannot be created or a communication problem happens with the S3 service.
      */

src/examples/java/software/amazon/nio/spi/examples/ListPrefix.java

@@ -1,27 +1,41 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 package software.amazon.nio.spi.examples;
 
 import java.io.IOException;
 import java.net.URI;
 import java.nio.file.Files;
 import java.nio.file.Paths;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 public class ListPrefix {
+
+    private static final Logger logger = LoggerFactory.getLogger(ListPrefix.class);
+
     public static void main(String[] args) throws IOException {
         if (args.length == 0) {
-            System.err.println("Provide an s3 prefix to list.");
+            logger.error("Provide an s3 prefix to list.");
             System.exit(1);
         }
 
         var s3Path = Paths.get(URI.create(args[0]));
 
         // if the prefix doesn't exist you won't get any listings
-        System.err.println("Files.exists(s3Path) = " + Files.exists(s3Path));
+        if (!Files.exists(s3Path)) {
+            logger.error("the prefix {} doesn't exist, you won't get any listings", s3Path);
+        }
 
         //if it's not a directory you won't get any listings.
-        System.err.println("Files.isDirectory(s3Path) = " + Files.isDirectory(s3Path));
+        if (!Files.isDirectory(s3Path)) {
+            logger.error("the path {} is not a directory, you won't get any listings", s3Path);
+        }
 
         try (var listed = Files.list(s3Path)) {
-            listed.forEach(System.out::println);
+            listed.forEach((p) -> logger.info(p.toString()));
         }
     }
 }

src/examples/java/software/amazon/nio/spi/examples/Main.java

@@ -9,21 +9,27 @@
 import java.net.URI;
 import java.nio.file.Files;
 import java.nio.file.Paths;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * Demo class that will read text from S3 URIs that you provide on the command line. Your standard AWS credential chain
  * is used for permissions.
  */
 public class Main {
+
+    private static final Logger logger = LoggerFactory.getLogger(Main.class);
+
     /**
      * Demo main method
+     *
      * @param args one or more S3 URIs to read
      * @throws IOException if something goes wrong
      */
     public static void main(String[] args) throws IOException {
 
-        if(args.length == 0){
-            System.err.println("Provide one or more S3 URIs to read from.");
+        if (args.length == 0) {
+            logger.error("Provide one or more S3 URIs to read from.");
             System.exit(1);
         }
 
@@ -35,10 +41,10 @@ public static void main(String[] args) throws IOException {
             // proves that the correct path type is being used
             assert path.getClass().getName().contains("S3Path");
 
-            System.err.println("*** READING FROM "+path.toUri()+" ***");
+            logger.info("*** READING FROM {} ***", path.toUri());
             Files.readAllLines(path)
-                    .forEach(System.out::println);
-            System.err.println("*** FINISHED READING OBJECT ***\n");
+                .forEach(logger::info);
+            logger.info("*** FINISHED READING OBJECT ***");
         }
     }
 }

src/examples/java/software/amazon/nio/spi/examples/ReadAllBytes.java

@@ -1,18 +1,28 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 package software.amazon.nio.spi.examples;
 
 import java.io.IOException;
 import java.net.URI;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Paths;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 public class ReadAllBytes {
+
+    private static final Logger logger = LoggerFactory.getLogger(ReadAllBytes.class);
+
     public static void main(String[] args) throws IOException {
         var filePath = Paths.get(URI.create(args[0]));
 
         final var bytes = Files.readAllBytes(filePath);
         // assumes this is a text file
         final var data = new String(bytes, StandardCharsets.UTF_8);
-        System.out.println(data);
+        logger.info(data);
     }
 }

src/examples/java/software/amazon/nio/spi/examples/WalkFromRoot.java

@@ -1,13 +1,22 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 package software.amazon.nio.spi.examples;
 
 
 import java.io.IOException;
 import java.net.URI;
 import java.nio.file.Files;
 import java.nio.file.Paths;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 public class WalkFromRoot {
 
+    private static final Logger logger = LoggerFactory.getLogger(WalkFromRoot.class);
+
     /**
      * Walks a bucket from the root listing all directories and files. Internally uses the {@code S3FileSystemProvider}'s
      * {@code newDirectoryStream()} method which uses asynchronous paginated calls to S3.
@@ -17,8 +26,8 @@ public class WalkFromRoot {
      */
     public static void main(String[] args) throws IOException {
 
-        if (args.length < 1){
-            System.err.println("Provide a bucket name to walk");
+        if (args.length < 1) {
+            logger.error("Provide a bucket name to walk");
             System.exit(1);
         }
 
@@ -29,13 +38,13 @@ public static void main(String[] args) throws IOException {
 
 
         var root = Paths.get(URI.create(bucketName));
-        System.err.println("root.getClass() = " + root.getClass());
+        logger.info("root.getClass() = {}", root.getClass());
 
         var s3 = root.getFileSystem();
 
         for (var rootDir : s3.getRootDirectories()) {
             try (var pathStream = Files.walk(rootDir)) {
-                pathStream.forEach(System.out::println);
+                pathStream.forEach((p) -> logger.info(p.toString()));
             }
         }
 

src/integrationTest/java/software/amazon/nio/spi/s3/Containers.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 package software.amazon.nio.spi.s3;
 
 import org.testcontainers.containers.localstack.LocalStackContainer;

src/integrationTest/java/software/amazon/nio/spi/s3/FilesCopyTest.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 package software.amazon.nio.spi.s3;
 
 import org.junit.jupiter.api.DisplayName;

src/integrationTest/java/software/amazon/nio/spi/s3/FilesDirectoryStreamTest.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 package software.amazon.nio.spi.s3;
 
 import org.junit.jupiter.api.DisplayName;

src/integrationTest/java/software/amazon/nio/spi/s3/FilesExistsTest.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 package software.amazon.nio.spi.s3;
 
 import org.junit.jupiter.api.BeforeEach;

src/integrationTest/java/software/amazon/nio/spi/s3/FilesReadTest.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 package software.amazon.nio.spi.s3;
 
 import org.junit.jupiter.api.BeforeAll;

src/integrationTest/java/software/amazon/nio/spi/s3/FilesWriteTest.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 package software.amazon.nio.spi.s3;
 
 import org.junit.jupiter.api.BeforeAll;

src/main/java/software/amazon/nio/spi/s3/Constants.java

@@ -1,5 +1,13 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 package software.amazon.nio.spi.s3;
 
-public class Constants {
+class Constants {
     public static final String PATH_SEPARATOR = "/";
+
+    private Constants() {
+    }
 }

src/main/java/software/amazon/nio/spi/s3/NotYetImplementedException.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 package software.amazon.nio.spi.s3;
 
 public class NotYetImplementedException extends RuntimeException {