JDK14/Java14源码在线阅读

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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package org.graalvm.compiler.serviceprovider;

import java.nio.Buffer;

/**
 * Covariant return types for some methods in the {@code java.nio.Buffer} were
 * <a href="https://bugs.openjdk.java.net/browse/JDK-4774077">introduced in JDK 9</a>.
 *
 * If calls to these methods are compiled with javac from JDK 9+ using {@code -target 8 -source 8}
 * then the call sites will invoke the covariant methods in the subclass. For example:
 *
 * <pre>
 * static void reset(ByteBuffer buf) {
 *     buf.reset();
 * }
 * </pre>
 *
 * will result in:
 *
 * <pre>
 *    0: aload_0
 *    1: invokevirtual #7  // Method java/nio/ByteBuffer.reset:()Ljava/nio/ByteBuffer;
 *    4: pop
 *    5: return
 * </pre>
 *
 * This will result in a {@link NoSuchMethodError} when run on JDK 8. The workaround for this is to
 * {@linkplain #asBaseBuffer(Buffer) coerce} the receiver for calls to the covariant methods to
 * {@link Buffer}.
 */
public final class BufferUtil {

    /**
     * Coerces {@code obj} to be of type {@link Buffer}. This is required instead of a cast as

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