JRE 8 rt.jar is the JAR file for JRE 8 RT (Runtime) libraries. JRE (Java Runtime) 8 is the runtime environment included in JDK 8. JRE 8 rt.jar libraries are divided into 6 packages:

com.* - Internal Oracle and Sun Microsystems libraries
java.* - Standard Java API libraries.
javax.* - Extended Java API libraries.
jdk.* -  JDK supporting libraries.
org.* - Third party libraries.
sun.* - Old libraries developed by Sun Microsystems.

JAR File Information:

Directory of C:\fyicenter\jdk-1.8.0_191\jre\lib
      63,596,151 rt.jar

Here is the list of Java classes of the javax.* package in JRE 1.8.0_191 rt.jar. Java source codes are also provided.

⏎ javax/security/auth/callback/TextOutputCallback.java

/*
 * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
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 *
 *
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 */

package javax.security.auth.callback;

/**
 * <p> Underlying security services instantiate and pass a
 * {@code TextOutputCallback} to the {@code handle}
 * method of a {@code CallbackHandler} to display information messages,
 * warning messages and error messages.
 *
 * @see javax.security.auth.callback.CallbackHandler
 */
public class TextOutputCallback implements Callback, java.io.Serializable {

    private static final long serialVersionUID = 1689502495511663102L;

    /** Information message. */
    public static final int INFORMATION         = 0;
    /** Warning message. */
    public static final int WARNING             = 1;
    /** Error message. */
    public static final int ERROR               = 2;

    /**
     * @serial
     * @since 1.4
     */
    private int messageType;
    /**
     * @serial
     * @since 1.4
     */
    private String message;

    /**
     * Construct a TextOutputCallback with a message type and message
     * to be displayed.
     *
     * <p>
     *
     * @param messageType the message type ({@code INFORMATION},
     *                  {@code WARNING} or {@code ERROR}). <p>
     *
     * @param message the message to be displayed. <p>
     *
     * @exception IllegalArgumentException if {@code messageType}
     *                  is not either {@code INFORMATION},
     *                  {@code WARNING} or {@code ERROR},
     *                  if {@code message} is null,
     *                  or if {@code message} has a length of 0.
     */
    public TextOutputCallback(int messageType, String message) {
        if ((messageType != INFORMATION &&
                messageType != WARNING && messageType != ERROR) ||
            message == null || message.length() == 0)
            throw new IllegalArgumentException();

        this.messageType = messageType;
        this.message = message;
    }

    /**
     * Get the message type.
     *
     * <p>
     *
     * @return the message type ({@code INFORMATION},
     *                  {@code WARNING} or {@code ERROR}).
     */
    public int getMessageType() {
        return messageType;
    }

    /**
     * Get the message to be displayed.
     *
     * <p>
     *
     * @return the message to be displayed.
     */
    public String getMessage() {
        return message;
    }
}

⏎ javax/security/auth/callback/TextOutputCallback.java

Or download all of them as a single archive file:

File name: jre-rt-javax-1.8.0_191-src.zip
File size: 5381005 bytes
Release date: 2018-10-28
Download 

⇒ JRE 8 rt.jar - org.* Package Source Code

⇐ JRE 8 rt.jar - java.* Package Source Code

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