log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/SLF4JLoggerContextFactory.java [30:43]:
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    public SLF4JLoggerContextFactory() {
        // LOG4J2-230, LOG4J2-204 (improve error reporting when misconfigured)
        boolean misconfigured = false;
        try {
            LoaderUtil.loadClass("org.slf4j.helpers.Log4jLoggerFactory");
            misconfigured = true;
        } catch (final ClassNotFoundException classNotFoundIsGood) {
            LOGGER.debug("org.slf4j.helpers.Log4jLoggerFactory is not on classpath. Good!");
        }
        if (misconfigured) {
            throw new IllegalStateException("slf4j-impl jar is mutually exclusive with log4j-to-slf4j jar "
                    + "(the first routes calls from SLF4J to Log4j, the second from Log4j to SLF4J)");
        }
    }
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log4j-to-jul/src/main/java/org/apache/logging/log4j/tojul/JULLoggerContextFactory.java [38:50]:
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    public JULLoggerContextFactory() {
        boolean misconfigured = false;
        try {
            LoaderUtil.loadClass("org.apache.logging.log4j.jul.LogManager");
            misconfigured = true;
        } catch (final ClassNotFoundException classNotFoundIsGood) {
            LOGGER.debug("org.apache.logging.log4j.jul.LogManager is not on classpath. Good!");
        }
        if (misconfigured) {
            throw new IllegalStateException("log4j-jul JAR is mutually exclusive with the log4j-to-jul JAR"
                    + "(the first routes calls from Log4j to JUL, the second from Log4j to JUL)");
        }
    }
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