From 23ea197b751a98d10a1bd549175f2566f3a7c227 Mon Sep 17 00:00:00 2001 From: Stephan Ewen Date: Fri, 24 Nov 2017 13:55:51 +0100 Subject: [PATCH] [hotfix] [core] Fix remaining checkstyle issues for 'core.fs' --- .../org/apache/flink/core/fs/FileSystem.java | 2 ++ .../flink/core/fs/FileSystemSafetyNet.java | 20 +++++++------- .../core/fs/SafetyNetCloseableRegistry.java | 26 +++++++++++-------- .../core/fs/SafetyNetWrapperFileSystem.java | 2 ++ .../core/fs/local/LocalBlockLocation.java | 4 +-- .../core/fs/local/LocalDataInputStream.java | 11 ++++---- .../core/fs/local/LocalDataOutputStream.java | 9 +++---- .../flink/core/fs/local/LocalFileStatus.java | 7 +++-- .../flink/core/fs/local/LocalFileSystem.java | 20 +++++++------- .../fs/AbstractCloseableRegistryTest.java | 14 +++++++--- .../flink/core/fs/CloseableRegistryTest.java | 3 +++ .../apache/flink/core/fs/FileSystemTest.java | 5 ++++ .../flink/core/fs/InitOutputPathTest.java | 12 +++++---- ...edConnectionsFileSystemDelegationTest.java | 1 - .../fs/LimitedConnectionsFileSystemTest.java | 2 +- .../org/apache/flink/core/fs/PathTest.java | 22 +++++++++++----- .../fs/SafetyNetCloseableRegistryTest.java | 7 ++--- .../core/fs/local/LocalFileSystemTest.java | 26 +++++++++---------- tools/maven/suppressions-core.xml | 8 ------ 19 files changed, 113 insertions(+), 88 deletions(-) diff --git a/flink-core/src/main/java/org/apache/flink/core/fs/FileSystem.java b/flink-core/src/main/java/org/apache/flink/core/fs/FileSystem.java index 18baaa5d5f9..07a1e76c0c3 100644 --- a/flink-core/src/main/java/org/apache/flink/core/fs/FileSystem.java +++ b/flink-core/src/main/java/org/apache/flink/core/fs/FileSystem.java @@ -229,7 +229,9 @@ public abstract class FileSystem { /** The default filesystem scheme to be used, configured during process-wide initialization. * This value defaults to the local file systems scheme {@code 'file:///'} or {@code 'file:/'}. */ + //CHECKSTYLE.OFF: StaticVariableName private static URI DEFAULT_SCHEME; + //CHECKSTYLE.ON: StaticVariableName // ------------------------------------------------------------------------ // Initialization diff --git a/flink-core/src/main/java/org/apache/flink/core/fs/FileSystemSafetyNet.java b/flink-core/src/main/java/org/apache/flink/core/fs/FileSystemSafetyNet.java index c06ccacdf06..d72aec03439 100644 --- a/flink-core/src/main/java/org/apache/flink/core/fs/FileSystemSafetyNet.java +++ b/flink-core/src/main/java/org/apache/flink/core/fs/FileSystemSafetyNet.java @@ -30,22 +30,22 @@ import static org.apache.flink.util.Preconditions.checkState; * When activated for a thread, it tracks all streams that are opened by FileSystems that the thread * obtains. The safety net has a global cleanup hook that will close all streams that were * not properly closed. - * + * *

The main thread of each Flink task, as well as the checkpointing thread are automatically guarded * by this safety net. - * + * *

Important: This safety net works only for streams created by Flink's FileSystem abstraction, * i.e., for {@code FileSystem} instances obtained via {@link FileSystem#get(URI)} or through * {@link Path#getFileSystem()}. - * + * *

Important: When a guarded thread obtains a {@code FileSystem} or a stream and passes them * to another thread, the safety net will close those resources once the former thread finishes. - * + * *

The safety net can be used as follows: * 

{@code
- * 
+ *
  * class GuardedThread extends Thread {
- * 
+ *
  *     public void run() {
  *         FileSystemSafetyNet.initializeSafetyNetForThread();
  *         try {
@@ -62,7 +62,7 @@ import static org.apache.flink.util.Preconditions.checkState;
 @Internal
 public class FileSystemSafetyNet {
 
-	/** The map from thread to the safety net registry for that thread */
+	/** The map from thread to the safety net registry for that thread. */
 	private static final ThreadLocal REGISTRIES = new ThreadLocal<>();
 
 	// ------------------------------------------------------------------------
@@ -73,9 +73,9 @@ public class FileSystemSafetyNet {
 	 * Activates the safety net for a thread. {@link FileSystem} instances obtained by the thread
 	 * that called this method will be guarded, meaning that their created streams are tracked and can
 	 * be closed via the safety net closing hook.
-	 * 
+	 *
 	 * 
This method should be called at the beginning of a thread that should be guarded.
-	 * 
+	 *
 	 * @throws IllegalStateException Thrown, if a safety net was already registered for the thread.
 	 */
 	@Internal
@@ -94,7 +94,7 @@ public class FileSystemSafetyNet {
 	 * Closes the safety net for a thread. This closes all remaining unclosed streams that were opened
 	 * by safety-net-guarded file systems. After this method was called, no streams can be opened any more
 	 * from any FileSystem instance that was obtained while the thread was guarded by the safety net.
-	 * 
+	 *
 	 * 
This method should be called at the very end of a guarded thread.
 	 */
 	@Internal
diff --git a/flink-core/src/main/java/org/apache/flink/core/fs/SafetyNetCloseableRegistry.java b/flink-core/src/main/java/org/apache/flink/core/fs/SafetyNetCloseableRegistry.java
index 9c4272f0acc..ccf944eb2ac 100644
--- a/flink-core/src/main/java/org/apache/flink/core/fs/SafetyNetCloseableRegistry.java
+++ b/flink-core/src/main/java/org/apache/flink/core/fs/SafetyNetCloseableRegistry.java
@@ -39,13 +39,13 @@ import java.util.Map;
 /**
  * This implementation of an {@link AbstractCloseableRegistry} registers {@link WrappingProxyCloseable}. When
  * the proxy becomes subject to GC, this registry takes care of closing unclosed {@link Closeable}s.
- * 

- * Phantom references are used to track when {@link org.apache.flink.util.WrappingProxy}s of {@link Closeable} got
+ *
+ * 
Phantom references are used to track when {@link org.apache.flink.util.WrappingProxy}s of {@link Closeable} got
  * GC'ed. We ensure that the wrapped {@link Closeable} is properly closed to avoid resource leaks.
- * 

- * Other than that, it works like a normal {@link CloseableRegistry}.
- * 

- * All methods in this class are thread-safe.
+ *
+ * 
Other than that, it works like a normal {@link CloseableRegistry}.
+ *
+ * 
All methods in this class are thread-safe.
  */
 @Internal
 public class SafetyNetCloseableRegistry extends
@@ -54,15 +54,19 @@ public class SafetyNetCloseableRegistry extends
 
 	private static final Logger LOG = LoggerFactory.getLogger(SafetyNetCloseableRegistry.class);
 
-	/** Lock for atomic modifications to reaper thread and registry count */
+	/** Lock for atomic modifications to reaper thread and registry count. */
 	private static final Object REAPER_THREAD_LOCK = new Object();
 
-	/** Singleton reaper thread takes care of all registries in VM */
+	//CHECKSTYLE.OFF: StaticVariableName
+
+	/** Singleton reaper thread takes care of all registries in VM. */
 	private static CloseableReaperThread REAPER_THREAD = null;
 
-	/** Global count of all instances of SafetyNetCloseableRegistry */
+	/** Global count of all instances of SafetyNetCloseableRegistry. */
 	private static int GLOBAL_SAFETY_NET_REGISTRY_COUNT = 0;
 
+	//CHECKSTYLE.ON: StaticVariableName
+
 	SafetyNetCloseableRegistry() {
 		super(new IdentityHashMap<>());
 
@@ -166,7 +170,7 @@ public class SafetyNetCloseableRegistry extends
 	}
 
 	/**
-	 * Reaper runnable collects and closes leaking resources
+	 * Reaper runnable collects and closes leaking resources.
 	 */
 	static final class CloseableReaperThread extends Thread {
 
@@ -187,7 +191,7 @@ public class SafetyNetCloseableRegistry extends
 			try {
 				while (running) {
 					final PhantomDelegatingCloseableRef toClose = (PhantomDelegatingCloseableRef) referenceQueue.remove();
-					
+
 					if (toClose != null) {
 						try {
 							LOG.warn("Closing unclosed resource via safety-net: {}", toClose.getDebugString());
diff --git a/flink-core/src/main/java/org/apache/flink/core/fs/SafetyNetWrapperFileSystem.java b/flink-core/src/main/java/org/apache/flink/core/fs/SafetyNetWrapperFileSystem.java
index e7f43a464d0..92b3a74c2cc 100644
--- a/flink-core/src/main/java/org/apache/flink/core/fs/SafetyNetWrapperFileSystem.java
+++ b/flink-core/src/main/java/org/apache/flink/core/fs/SafetyNetWrapperFileSystem.java
@@ -82,6 +82,7 @@ public class SafetyNetWrapperFileSystem extends FileSystem implements WrappingPr
 	}
 
 	@Override
+	@SuppressWarnings("deprecation")
 	public long getDefaultBlockSize() {
 		return unsafeFileSystem.getDefaultBlockSize();
 	}
@@ -107,6 +108,7 @@ public class SafetyNetWrapperFileSystem extends FileSystem implements WrappingPr
 	}
 
 	@Override
+	@SuppressWarnings("deprecation")
 	public FSDataOutputStream create(Path f, boolean overwrite, int bufferSize, short replication, long blockSize)
 			throws IOException {
 
diff --git a/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalBlockLocation.java b/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalBlockLocation.java
index 9825781dfdf..25dd92d529f 100644
--- a/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalBlockLocation.java
+++ b/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalBlockLocation.java
@@ -18,11 +18,11 @@
 
 package org.apache.flink.core.fs.local;
 
-import java.io.IOException;
-
 import org.apache.flink.annotation.Internal;
 import org.apache.flink.core.fs.BlockLocation;
 
+import java.io.IOException;
+
 /**
  * Implementation of the {@link BlockLocation} interface for a local file system.
  */
diff --git a/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalDataInputStream.java b/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalDataInputStream.java
index 172da796f4f..63017e385ad 100644
--- a/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalDataInputStream.java
+++ b/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalDataInputStream.java
@@ -22,6 +22,7 @@ import org.apache.flink.annotation.Internal;
 import org.apache.flink.core.fs.FSDataInputStream;
 
 import javax.annotation.Nonnull;
+
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.IOException;
@@ -40,9 +41,9 @@ public class LocalDataInputStream extends FSDataInputStream {
 
 	/**
 	 * Constructs a new LocalDataInputStream object from a given {@link File} object.
-	 * 
+	 *
 	 * @param file The File the data stream is read from
-	 * 
+	 *
 	 * @throws IOException Thrown if the data input stream cannot be created.
 	 */
 	public LocalDataInputStream(File file) throws IOException {
@@ -71,18 +72,18 @@ public class LocalDataInputStream extends FSDataInputStream {
 	public int read(@Nonnull byte[] buffer, int offset, int length) throws IOException {
 		return this.fis.read(buffer, offset, length);
 	}
-	
+
 	@Override
 	public void close() throws IOException {
 		// Accoring to javadoc, this also closes the channel
 		this.fis.close();
 	}
-	
+
 	@Override
 	public int available() throws IOException {
 		return this.fis.available();
 	}
-	
+
 	@Override
 	public long skip(final long n) throws IOException {
 		return this.fis.skip(n);
diff --git a/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalDataOutputStream.java b/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalDataOutputStream.java
index 5cc011bc284..aa64593acdc 100644
--- a/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalDataOutputStream.java
+++ b/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalDataOutputStream.java
@@ -18,13 +18,13 @@
 
 package org.apache.flink.core.fs.local;
 
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.core.fs.FSDataOutputStream;
+
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
 
-import org.apache.flink.annotation.Internal;
-import org.apache.flink.core.fs.FSDataOutputStream;
-
 /**
  * The LocalDataOutputStream class is a wrapper class for a data
  * output stream to the local file system.
@@ -37,7 +37,7 @@ public class LocalDataOutputStream extends FSDataOutputStream {
 
 	/**
 	 * Constructs a new LocalDataOutputStream object from a given {@link File} object.
-	 * 
+	 *
 	 * @param file
 	 *        the {@link File} object the data stream is read from
 	 * @throws IOException
@@ -62,7 +62,6 @@ public class LocalDataOutputStream extends FSDataOutputStream {
 		fos.close();
 	}
 
-
 	@Override
 	public void flush() throws IOException {
 		fos.flush();
diff --git a/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalFileStatus.java b/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalFileStatus.java
index 63e999da3cb..781e0d3014a 100644
--- a/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalFileStatus.java
+++ b/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalFileStatus.java
@@ -16,16 +16,15 @@
  * limitations under the License.
  */
 
-
 package org.apache.flink.core.fs.local;
 
-import java.io.File;
-
 import org.apache.flink.annotation.Internal;
 import org.apache.flink.core.fs.FileStatus;
 import org.apache.flink.core.fs.FileSystem;
 import org.apache.flink.core.fs.Path;
 
+import java.io.File;
+
 /**
  * The class LocalFileStatus provides an implementation of the {@link FileStatus} interface
  * for the local file system.
@@ -45,7 +44,7 @@ public class LocalFileStatus implements FileStatus {
 
 	/**
 	 * Creates a LocalFileStatus object from a given {@link File} object.
-	 * 
+	 *
 	 * @param f
 	 *        the {@link File} object this LocalFileStatus refers to
 	 * @param fs
diff --git a/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalFileSystem.java b/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalFileSystem.java
index a96f2212d04..c3e5a2fcc0e 100644
--- a/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalFileSystem.java
+++ b/flink-core/src/main/java/org/apache/flink/core/fs/local/LocalFileSystem.java
@@ -16,10 +16,10 @@
  * limitations under the License.
  */
 
-
-/**
- * This file is based on source code from the Hadoop Project (http://hadoop.apache.org/), licensed by the Apache
- * Software Foundation (ASF) under the Apache License, Version 2.0. See the NOTICE file distributed with this work for
+/*
+ * Parts of earlier versions of this file were based on source code from the
+ * Hadoop Project (http://hadoop.apache.org/), licensed by the Apache Software Foundation (ASF)
+ * under the Apache License, Version 2.0. See the NOTICE file distributed with this work for
  * additional information regarding copyright ownership.
  */
 
@@ -65,7 +65,7 @@ public class LocalFileSystem extends FileSystem {
 	/** The URI representing the local file system. */
 	private static final URI LOCAL_URI = OperatingSystem.isWindows() ? URI.create("file:/") : URI.create("file:///");
 
-	/** The shared instance of the local file system */
+	/** The shared instance of the local file system. */
 	private static final LocalFileSystem INSTANCE = new LocalFileSystem();
 
 	/** Path pointing to the current working directory.
@@ -73,10 +73,10 @@ public class LocalFileSystem extends FileSystem {
 	private final String workingDir;
 
 	/** Path pointing to the current working directory.
-	 * Because Paths are not immutable, we cannot cache the proper path here */
+	 * Because Paths are not immutable, we cannot cache the proper path here. */
 	private final String homeDir;
 
-	/** The host name of this machine */
+	/** The host name of this machine. */
 	private final String hostName;
 
 	/**
@@ -112,7 +112,7 @@ public class LocalFileSystem extends FileSystem {
 		}
 		else {
 			throw new FileNotFoundException("File " + f + " does not exist or the user running "
-					+ "Flink ('"+System.getProperty("user.name")+"') has insufficient permissions to access it.");
+					+ "Flink ('" + System.getProperty("user.name") + "') has insufficient permissions to access it.");
 		}
 	}
 
@@ -149,7 +149,6 @@ public class LocalFileSystem extends FileSystem {
 		return new File(path.toUri().getPath());
 	}
 
-
 	@Override
 	public FileStatus[] listStatus(final Path f) throws IOException {
 
@@ -175,7 +174,6 @@ public class LocalFileSystem extends FileSystem {
 		return results;
 	}
 
-
 	@Override
 	public boolean delete(final Path f, final boolean recursive) throws IOException {
 
@@ -233,7 +231,7 @@ public class LocalFileSystem extends FileSystem {
 	public boolean mkdirs(final Path f) throws IOException {
 		final File p2f = pathToFile(f);
 
-		if(p2f.isDirectory()) {
+		if (p2f.isDirectory()) {
 			return true;
 		}
 
diff --git a/flink-core/src/test/java/org/apache/flink/core/fs/AbstractCloseableRegistryTest.java b/flink-core/src/test/java/org/apache/flink/core/fs/AbstractCloseableRegistryTest.java
index f9425f39a20..eb07378493b 100644
--- a/flink-core/src/test/java/org/apache/flink/core/fs/AbstractCloseableRegistryTest.java
+++ b/flink-core/src/test/java/org/apache/flink/core/fs/AbstractCloseableRegistryTest.java
@@ -32,6 +32,9 @@ import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.verify;
 import static org.powermock.api.mockito.PowerMockito.spy;
 
+/**
+ * Tests for the {@link AbstractCloseableRegistry}.
+ */
 public abstract class AbstractCloseableRegistryTest {
 
 	protected ProducerThread[] streamOpenThreads;
@@ -140,8 +143,7 @@ public abstract class AbstractCloseableRegistryTest {
 		try {
 			closeableRegistry.registerCloseable(testCloseable);
 			Assert.fail("Closed registry should not accept closeables!");
-		}catch (IOException ignore) {
-		}
+		} catch (IOException ignored) {}
 
 		blockCloseLatch.trigger();
 		closer.join();
@@ -151,7 +153,10 @@ public abstract class AbstractCloseableRegistryTest {
 		Assert.assertEquals(0, closeableRegistry.getNumberOfRegisteredCloseables());
 	}
 
-	protected static abstract class ProducerThread extends Thread {
+	/**
+	 * A testing producer.
+	 */
+	protected abstract static class ProducerThread extends Thread {
 
 		protected final AbstractCloseableRegistry registry;
 		protected final AtomicInteger refCount;
@@ -188,6 +193,9 @@ public abstract class AbstractCloseableRegistryTest {
 		}
 	}
 
+	/**
+	 * Testing stream which adds itself to a reference counter while not closed.
+	 */
 	protected static final class TestStream extends FSDataInputStream {
 
 		protected AtomicInteger refCount;
diff --git a/flink-core/src/test/java/org/apache/flink/core/fs/CloseableRegistryTest.java b/flink-core/src/test/java/org/apache/flink/core/fs/CloseableRegistryTest.java
index c3bf6e677fc..8a0fb9679b9 100644
--- a/flink-core/src/test/java/org/apache/flink/core/fs/CloseableRegistryTest.java
+++ b/flink-core/src/test/java/org/apache/flink/core/fs/CloseableRegistryTest.java
@@ -24,6 +24,9 @@ import java.io.Closeable;
 import java.io.IOException;
 import java.util.concurrent.atomic.AtomicInteger;
 
+/**
+ * Tests for the {@link CloseableRegistry}.
+ */
 public class CloseableRegistryTest extends AbstractCloseableRegistryTest {
 
 	@Override
diff --git a/flink-core/src/test/java/org/apache/flink/core/fs/FileSystemTest.java b/flink-core/src/test/java/org/apache/flink/core/fs/FileSystemTest.java
index 1bde2fb5d06..598b1e11a03 100644
--- a/flink-core/src/test/java/org/apache/flink/core/fs/FileSystemTest.java
+++ b/flink-core/src/test/java/org/apache/flink/core/fs/FileSystemTest.java
@@ -15,10 +15,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.apache.flink.core.fs;
 
 import org.apache.flink.core.fs.local.LocalFileSystem;
 import org.apache.flink.util.WrappingProxyUtil;
+
 import org.junit.Test;
 
 import java.io.IOException;
@@ -27,6 +29,9 @@ import java.net.URISyntaxException;
 
 import static org.junit.Assert.assertTrue;
 
+/**
+ * Tests for the {@link FileSystem} base class.
+ */
 public class FileSystemTest {
 
 	@Test
diff --git a/flink-core/src/test/java/org/apache/flink/core/fs/InitOutputPathTest.java b/flink-core/src/test/java/org/apache/flink/core/fs/InitOutputPathTest.java
index 9b67388dd5d..d6de9b683bc 100644
--- a/flink-core/src/test/java/org/apache/flink/core/fs/InitOutputPathTest.java
+++ b/flink-core/src/test/java/org/apache/flink/core/fs/InitOutputPathTest.java
@@ -28,7 +28,6 @@ import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
 import org.junit.runner.RunWith;
-
 import org.mockito.invocation.InvocationOnMock;
 import org.mockito.stubbing.Answer;
 import org.powermock.core.classloader.annotations.PrepareForTest;
@@ -40,9 +39,12 @@ import java.io.IOException;
 import java.lang.reflect.Field;
 import java.util.concurrent.locks.ReentrantLock;
 
-import static org.powermock.api.mockito.PowerMockito.*;
-import static org.junit.Assert.*;
+import static org.junit.Assert.fail;
+import static org.powermock.api.mockito.PowerMockito.whenNew;
 
+/**
+ * A test validating that the initialization of local output paths is properly synchronized.
+ */
 @RunWith(PowerMockRunner.class)
 @PrepareForTest(LocalFileSystem.class)
 public class InitOutputPathTest {
@@ -79,7 +81,7 @@ public class InitOutputPathTest {
 
 	@Test
 	public void testProperSynchronized() throws Exception {
-		// in the synchronized variant, we cannot use the "await latches" because not 
+		// in the synchronized variant, we cannot use the "await latches" because not
 		// both threads can make process interleaved (due to the synchronization)
 		// the test uses sleeps (rather than latches) to produce the same interleaving.
 		// while that is not guaranteed to produce the pathological interleaving,
@@ -121,7 +123,7 @@ public class InitOutputPathTest {
 		});
 
 		final LocalFileSystem fs1 = new SyncedFileSystem(
-				deleteAwaitLatch1, mkdirsAwaitLatch1, 
+				deleteAwaitLatch1, mkdirsAwaitLatch1,
 				deleteTriggerLatch1, mkdirsTriggerLatch1);
 
 		final LocalFileSystem fs2 = new SyncedFileSystem(
diff --git a/flink-core/src/test/java/org/apache/flink/core/fs/LimitedConnectionsFileSystemDelegationTest.java b/flink-core/src/test/java/org/apache/flink/core/fs/LimitedConnectionsFileSystemDelegationTest.java
index b13367788b4..2e04648ce24 100644
--- a/flink-core/src/test/java/org/apache/flink/core/fs/LimitedConnectionsFileSystemDelegationTest.java
+++ b/flink-core/src/test/java/org/apache/flink/core/fs/LimitedConnectionsFileSystemDelegationTest.java
@@ -28,7 +28,6 @@ import java.io.IOException;
 import java.util.Random;
 
 import static org.junit.Assert.assertEquals;
-
 import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.anyBoolean;
 import static org.mockito.Matchers.anyInt;
diff --git a/flink-core/src/test/java/org/apache/flink/core/fs/LimitedConnectionsFileSystemTest.java b/flink-core/src/test/java/org/apache/flink/core/fs/LimitedConnectionsFileSystemTest.java
index 509b4aefd65..7391877d2e4 100644
--- a/flink-core/src/test/java/org/apache/flink/core/fs/LimitedConnectionsFileSystemTest.java
+++ b/flink-core/src/test/java/org/apache/flink/core/fs/LimitedConnectionsFileSystemTest.java
@@ -627,7 +627,7 @@ public class LimitedConnectionsFileSystemTest {
 		}
 	}
 
-	private static abstract class BlockingThread extends CheckedThread {
+	private abstract static class BlockingThread extends CheckedThread {
 
 		private final OneShotLatch waiter = new OneShotLatch();
 
diff --git a/flink-core/src/test/java/org/apache/flink/core/fs/PathTest.java b/flink-core/src/test/java/org/apache/flink/core/fs/PathTest.java
index 66816ada3c2..b4da2dc00ba 100644
--- a/flink-core/src/test/java/org/apache/flink/core/fs/PathTest.java
+++ b/flink-core/src/test/java/org/apache/flink/core/fs/PathTest.java
@@ -15,13 +15,23 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.apache.flink.core.fs;
 
+import org.junit.Test;
+
 import java.io.IOException;
 import java.net.URI;
-import org.junit.Test;
-import static org.junit.Assert.*;
 
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+/**
+ * Tests for the {@link Path} class.
+ */
 public class PathTest {
 
 	@Test
@@ -70,23 +80,23 @@ public class PathTest {
 		assertEquals("/C:/my/windows/path", p.toUri().getPath());
 
 		try {
-			new Path((String)null);
+			new Path((String) null);
 			fail();
-		} catch(Exception e) {
+		} catch (Exception e) {
 			// exception expected
 		}
 
 		try {
 			new Path("");
 			fail();
-		} catch(Exception e) {
+		} catch (Exception e) {
 			// exception expected
 		}
 
 		try {
 			new Path(" ");
 			fail();
-		} catch(Exception e) {
+		} catch (Exception e) {
 			// exception expected
 		}
 
diff --git a/flink-core/src/test/java/org/apache/flink/core/fs/SafetyNetCloseableRegistryTest.java b/flink-core/src/test/java/org/apache/flink/core/fs/SafetyNetCloseableRegistryTest.java
index 4ceda5033a5..5474f9905ae 100644
--- a/flink-core/src/test/java/org/apache/flink/core/fs/SafetyNetCloseableRegistryTest.java
+++ b/flink-core/src/test/java/org/apache/flink/core/fs/SafetyNetCloseableRegistryTest.java
@@ -32,6 +32,9 @@ import java.io.Closeable;
 import java.io.IOException;
 import java.util.concurrent.atomic.AtomicInteger;
 
+/**
+ * Tests for the {@link SafetyNetCloseableRegistry}.
+ */
 public class SafetyNetCloseableRegistryTest
 	extends AbstractCloseableRegistryTest,
 	SafetyNetCloseableRegistry.PhantomDelegatingCloseableRef> {
@@ -44,9 +47,7 @@ public class SafetyNetCloseableRegistryTest
 		return new WrappingProxyCloseable() {
 
 			@Override
-			public void close() throws IOException {
-
-			}
+			public void close() throws IOException {}
 
 			@Override
 			public Closeable getWrappedDelegate() {
diff --git a/flink-core/src/test/java/org/apache/flink/core/fs/local/LocalFileSystemTest.java b/flink-core/src/test/java/org/apache/flink/core/fs/local/LocalFileSystemTest.java
index 96c526944fa..2352404d4ed 100644
--- a/flink-core/src/test/java/org/apache/flink/core/fs/local/LocalFileSystemTest.java
+++ b/flink-core/src/test/java/org/apache/flink/core/fs/local/LocalFileSystemTest.java
@@ -18,25 +18,13 @@
 
 package org.apache.flink.core.fs.local;
 
-import static org.junit.Assert.assertArrayEquals;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
-
-import java.io.File;
-import java.io.FileInputStream;
-import java.io.FileOutputStream;
-import java.io.IOException;
-import java.util.Arrays;
-import java.util.UUID;
-
 import org.apache.flink.core.fs.FSDataInputStream;
 import org.apache.flink.core.fs.FSDataOutputStream;
 import org.apache.flink.core.fs.FileStatus;
 import org.apache.flink.core.fs.FileSystem;
+import org.apache.flink.core.fs.FileSystem.WriteMode;
 import org.apache.flink.core.fs.FileSystemKind;
 import org.apache.flink.core.fs.Path;
-import org.apache.flink.core.fs.FileSystem.WriteMode;
 import org.apache.flink.util.FileUtils;
 
 import org.junit.Assume;
@@ -44,6 +32,18 @@ import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
 
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.UUID;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
 /**
  * This class tests the functionality of the {@link LocalFileSystem} class in its components. In particular,
  * file/directory access, creation, deletion, read, write is tested.
diff --git a/tools/maven/suppressions-core.xml b/tools/maven/suppressions-core.xml
index 066b30addf7..78341c9a76a 100644
--- a/tools/maven/suppressions-core.xml
+++ b/tools/maven/suppressions-core.xml
@@ -111,14 +111,6 @@ under the License.
 		files="(.*)test[/\\](.*)configuration[/\\](.*)"
 		checks="AvoidStarImport"/>
 
-	
-	
-	
-
 	
-- 
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