Tripwire.java

/*
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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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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 java.util;

import sun.util.logging.PlatformLogger;

import java.security.AccessController;
import java.security.PrivilegedAction;

/**
 * Utility class for detecting inadvertent uses of boxing in {@code java.util} classes.
 * The detection is turned on or off based on whether the system property {@code org.openjdk.java.util.stream.tripwire} is considered {@code true}
 * according to {@link Boolean#getBoolean(String)}.
 * This should normally be turned off for production use.
 *
 * @apiNote Typical usage would be for boxing code to do:
 * <pre>{@code
 *     if (Tripwire.ENABLED)
 *         Tripwire.trip(getClass(), "{0} calling PrimitiveIterator.OfInt.nextInt()");
 * }</pre>
 * @since 1.8
 */
// 工具类，系统内部使用。用于debug环境，检测是否无意中使用了装箱特性。生产环境下应关闭此检测。
final class Tripwire {
    private static final String TRIPWIRE_PROPERTY = "org.openjdk.java.util.stream.tripwire";
    
    /** Should debugging checks be enabled? */
    static final boolean ENABLED = AccessController.doPrivileged((PrivilegedAction<Boolean>) () -> Boolean.getBoolean(TRIPWIRE_PROPERTY));
    
    private Tripwire() {
    }
    
    /**
     * Produces a log warning, using {@code PlatformLogger.getLogger(className)}, using the supplied message.
     * The class name of {@code trippingClass} will be used as the first parameter to the message.
     *
     * @param trippingClass Name of the class generating the message
     * @param msg           A message format string of the type expected by {@link PlatformLogger}
     */
    // 在日志中生成警告信息
    static void trip(Class<?> trippingClass, String msg) {
        PlatformLogger.getLogger(trippingClass.getName()).warning(msg, trippingClass.getName());
    }
}