Remove all version checks for Java 6 and 7 (#14006)

Motivation:
Netty 4.2 now requires Java 8 as the minimum supported version, so there
is no need to guard for older JDKs.

Modification:
Remove all the version checks for Java 7 and older, and remove all uses
of `@SuppressJava6Requirement`. Revapi complains these annotation
removals are a potential compatibility issue, so ignores have been
added.

Result:
Less code dealing with JDK versions.

.github/workflows/codeql-analysis.yml

@@ -22,10 +22,10 @@ name: "CodeQL"
 
 on:
   push:
-    branches: ["4.1", "4.2", main]
+    branches: ["4.1", "4.2"]
   pull_request:
     # The branches below must be a subset of the branches above
-    branches: ["4.1", "4.2", main]
+    branches: ["4.1", "4.2"]
   schedule:
     - cron: '0 13 * * 3'
 
@@ -89,6 +89,10 @@ jobs:
     # ✏️ If the Autobuild fails above, remove it and uncomment the following three lines
     #    and modify them (or add more) to build your code if your project
     #    uses a compiled language
+    - uses: actions/setup-java@v4
+      with:
+        distribution: 'zulu'
+        java-version: '8' # The JDK version to make available on the path.
 
     - name: Compile project
       run: ./mvnw -B -ntp clean package -DskipTests=true

buffer/src/main/java/io/netty/buffer/AdaptivePoolingAllocator.java

@@ -22,7 +22,6 @@
 import io.netty.util.internal.ObjectPool;
 import io.netty.util.internal.ObjectUtil;
 import io.netty.util.internal.PlatformDependent;
-import io.netty.util.internal.SuppressJava6Requirement;
 import io.netty.util.internal.SystemPropertyUtil;
 import io.netty.util.internal.UnstableApi;
 
@@ -42,8 +41,6 @@
 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
 import java.util.concurrent.locks.StampedLock;
 
-import static io.netty.util.internal.PlatformDependent.javaVersion;
-
 /**
  * An auto-tuning pooling allocator, that follows an anti-generational hypothesis.
  * <p>
@@ -70,7 +67,6 @@
  * magazine, to be shared with other magazines.
  * The {@link #createSharedChunkQueue()} method can be overridden to customize this queue.
  */
-@SuppressJava6Requirement(reason = "Guarded by version check")
 @UnstableApi
 final class AdaptivePoolingAllocator {
     private static final int RETIRE_CAPACITY = 4 * 1024;
@@ -104,10 +100,6 @@ final class AdaptivePoolingAllocator {
 
     AdaptivePoolingAllocator(ChunkAllocator chunkAllocator) {
         this.chunkAllocator = chunkAllocator;
-        if (javaVersion() < 8) {
-            // The implementation uses StampedLock, which was introduced in Java 8.
-            throw new IllegalStateException("This allocator require Java 8 or newer.");
-        }
         centralQueue = ObjectUtil.checkNotNull(createSharedChunkQueue(), "centralQueue");
         magazineExpandLock = new StampedLock();
         Magazine[] mags = new Magazine[4];
@@ -234,7 +226,6 @@ private boolean offerToQueue(ChunkByteBuf buffer) {
         return centralQueue.offer(buffer);
     }
 
-    @SuppressJava6Requirement(reason = "Guarded by version check")
     @SuppressWarnings("checkstyle:finalclass") // Checkstyle mistakenly believes this class should be final.
     private static class AllocationStatistics extends StampedLock {
         private static final long serialVersionUID = -8319929980932269688L;

buffer/src/main/java/io/netty/buffer/PooledUnsafeHeapByteBuf.java

@@ -132,26 +132,18 @@ protected void _setLongLE(int index, long value) {
 
     @Override
     public ByteBuf setZero(int index, int length) {
-        if (PlatformDependent.javaVersion() >= 7) {
-            checkIndex(index, length);
-            // Only do on java7+ as the needed Unsafe call was only added there.
-            UnsafeByteBufUtil.setZero(memory, idx(index), length);
-            return this;
-        }
-        return super.setZero(index, length);
+        checkIndex(index, length);
+        UnsafeByteBufUtil.setZero(memory, idx(index), length);
+        return this;
     }
 
     @Override
     public ByteBuf writeZero(int length) {
-        if (PlatformDependent.javaVersion() >= 7) {
-            // Only do on java7+ as the needed Unsafe call was only added there.
-            ensureWritable(length);
-            int wIndex = writerIndex;
-            UnsafeByteBufUtil.setZero(memory, idx(wIndex), length);
-            writerIndex = wIndex + length;
-            return this;
-        }
-        return super.writeZero(length);
+        ensureWritable(length);
+        int wIndex = writerIndex;
+        UnsafeByteBufUtil.setZero(memory, idx(wIndex), length);
+        writerIndex = wIndex + length;
+        return this;
     }
 
     @Override

buffer/src/main/java/io/netty/buffer/UnpooledUnsafeHeapByteBuf.java

@@ -248,26 +248,18 @@ protected void _setLongLE(int index, long value) {
 
     @Override
     public ByteBuf setZero(int index, int length) {
-        if (PlatformDependent.javaVersion() >= 7) {
-            // Only do on java7+ as the needed Unsafe call was only added there.
-            checkIndex(index, length);
-            UnsafeByteBufUtil.setZero(array, index, length);
-            return this;
-        }
-        return super.setZero(index, length);
+        checkIndex(index, length);
+        UnsafeByteBufUtil.setZero(array, index, length);
+        return this;
     }
 
     @Override
     public ByteBuf writeZero(int length) {
-        if (PlatformDependent.javaVersion() >= 7) {
-            // Only do on java7+ as the needed Unsafe call was only added there.
-            ensureWritable(length);
-            int wIndex = writerIndex;
-            UnsafeByteBufUtil.setZero(array, wIndex, length);
-            writerIndex = wIndex + length;
-            return this;
-        }
-        return super.writeZero(length);
+        ensureWritable(length);
+        int wIndex = writerIndex;
+        UnsafeByteBufUtil.setZero(array, wIndex, length);
+        writerIndex = wIndex + length;
+        return this;
     }
 
     @Override

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketUtil.java

@@ -15,16 +15,12 @@
  */
 package io.netty.handler.codec.http.websocketx;
 
-import io.netty.buffer.ByteBuf;
-import io.netty.buffer.Unpooled;
-import io.netty.handler.codec.base64.Base64;
-import io.netty.util.CharsetUtil;
 import io.netty.util.concurrent.FastThreadLocal;
 import io.netty.util.internal.PlatformDependent;
-import io.netty.util.internal.SuppressJava6Requirement;
 
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
+import java.util.Base64;
 
 /**
  * A utility class mainly for use by web sockets
@@ -95,24 +91,8 @@ private static byte[] digest(FastThreadLocal<MessageDigest> digestFastThreadLoca
      * @param data The data to encode
      * @return An encoded string containing the data
      */
-    @SuppressJava6Requirement(reason = "Guarded with java version check")
     static String base64(byte[] data) {
-        if (PlatformDependent.javaVersion() >= 8) {
-            return java.util.Base64.getEncoder().encodeToString(data);
-        }
-        String encodedString;
-        ByteBuf encodedData = Unpooled.wrappedBuffer(data);
-        try {
-            ByteBuf encoded = Base64.encode(encodedData);
-            try {
-                encodedString = encoded.toString(CharsetUtil.UTF_8);
-            } finally {
-                encoded.release();
-            }
-        } finally {
-            encodedData.release();
-        }
-        return encodedString;
+        return Base64.getEncoder().encodeToString(data);
     }
 
     /**

codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyHeaderBlockEncoder.java

@@ -17,7 +17,6 @@
 
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufAllocator;
-import io.netty.util.internal.PlatformDependent;
 
 /**
  * Super-class for SPDY header-block encoders.
@@ -30,14 +29,7 @@ public abstract class SpdyHeaderBlockEncoder {
 
     static SpdyHeaderBlockEncoder newInstance(
             SpdyVersion version, int compressionLevel, int windowBits, int memLevel) {
-
-        if (PlatformDependent.javaVersion() >= 7) {
-            return new SpdyHeaderBlockZlibEncoder(
-                    version, compressionLevel);
-        } else {
-            return new SpdyHeaderBlockJZlibEncoder(
-                    version, compressionLevel, windowBits, memLevel);
-        }
+        return new SpdyHeaderBlockZlibEncoder(version, compressionLevel);
     }
 
     abstract ByteBuf encode(ByteBufAllocator alloc, SpdyHeadersFrame frame) throws Exception;

codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyHeaderBlockZlibEncoder.java

@@ -18,12 +18,10 @@
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufAllocator;
 import io.netty.buffer.Unpooled;
-import io.netty.util.internal.PlatformDependent;
-import io.netty.util.internal.SuppressJava6Requirement;
 
 import java.util.zip.Deflater;
 
-import static io.netty.handler.codec.spdy.SpdyCodecUtil.*;
+import static io.netty.handler.codec.spdy.SpdyCodecUtil.SPDY_DICT;
 import static io.netty.util.internal.ObjectUtil.checkNotNullWithIAE;
 
 class SpdyHeaderBlockZlibEncoder extends SpdyHeaderBlockRawEncoder {
@@ -73,17 +71,11 @@ private ByteBuf encode(ByteBufAllocator alloc, int len) {
         }
     }
 
-    @SuppressJava6Requirement(reason = "Guarded by java version check")
     private boolean compressInto(ByteBuf compressed) {
         byte[] out = compressed.array();
         int off = compressed.arrayOffset() + compressed.writerIndex();
         int toWrite = compressed.writableBytes();
-        final int numBytes;
-        if (PlatformDependent.javaVersion() >= 7) {
-            numBytes = compressor.deflate(out, off, toWrite, Deflater.SYNC_FLUSH);
-        } else {
-            numBytes = compressor.deflate(out, off, toWrite);
-        }
+        final int numBytes = compressor.deflate(out, off, toWrite, Deflater.SYNC_FLUSH);
         compressed.writerIndex(compressed.writerIndex() + numBytes);
         return numBytes == toWrite;
     }

codec-http/src/main/java/io/netty/handler/codec/spdy/SpdyProtocolException.java

@@ -15,8 +15,6 @@
  */
 package io.netty.handler.codec.spdy;
 
-import io.netty.util.internal.PlatformDependent;
-import io.netty.util.internal.SuppressJava6Requirement;
 import io.netty.util.internal.ThrowableUtil;
 
 public class SpdyProtocolException extends Exception {
@@ -50,17 +48,10 @@ public SpdyProtocolException(Throwable cause) {
     }
 
     static SpdyProtocolException newStatic(String message, Class<?> clazz, String method) {
-        final SpdyProtocolException exception;
-        if (PlatformDependent.javaVersion() >= 7) {
-            exception = new StacklessSpdyProtocolException(message, true);
-        } else {
-            exception = new StacklessSpdyProtocolException(message);
-        }
+        final SpdyProtocolException exception = new StacklessSpdyProtocolException(message, true);
         return ThrowableUtil.unknownStackTrace(exception, clazz, method);
     }
 
-    @SuppressJava6Requirement(reason = "uses Java 7+ Exception.<init>(String, Throwable, boolean, boolean)" +
-            " but is guarded by version checks")
     private SpdyProtocolException(String message, boolean shared) {
         super(message, null, false, true);
         assert shared;
@@ -69,10 +60,6 @@ private SpdyProtocolException(String message, boolean shared) {
     private static final class StacklessSpdyProtocolException extends SpdyProtocolException {
         private static final long serialVersionUID = -6302754207557485099L;
 
-        StacklessSpdyProtocolException(String message) {
-            super(message);
-        }
-
         StacklessSpdyProtocolException(String message, boolean shared) {
             super(message, shared);
         }

codec-http2/src/main/java/io/netty/handler/codec/http2/Http2Exception.java

@@ -15,8 +15,6 @@
 
 package io.netty.handler.codec.http2;
 
-import io.netty.util.internal.PlatformDependent;
-import io.netty.util.internal.SuppressJava6Requirement;
 import io.netty.util.internal.ThrowableUtil;
 import io.netty.util.internal.UnstableApi;
 
@@ -68,17 +66,10 @@ public Http2Exception(Http2Error error, String message, Throwable cause, Shutdow
 
     static Http2Exception newStatic(Http2Error error, String message, ShutdownHint shutdownHint,
                                     Class<?> clazz, String method) {
-        final Http2Exception exception;
-        if (PlatformDependent.javaVersion() >= 7) {
-            exception = new StacklessHttp2Exception(error, message, shutdownHint, true);
-        } else {
-            exception = new StacklessHttp2Exception(error, message, shutdownHint);
-        }
+        final Http2Exception exception = new StacklessHttp2Exception(error, message, shutdownHint, true);
         return ThrowableUtil.unknownStackTrace(exception, clazz, method);
     }
 
-    @SuppressJava6Requirement(reason = "uses Java 7+ Exception.<init>(String, Throwable, boolean, boolean)" +
-            " but is guarded by version checks")
     private Http2Exception(Http2Error error, String message, ShutdownHint shutdownHint, boolean shared) {
         super(message, null, false, true);
         assert shared;