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/management/loading/MLetObjectInputStream.java

/*
 * Copyright (c) 1999, 2008, 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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 *
 *
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 */

package javax.management.loading;


// java import

import java.io.*;
import java.lang.reflect.Array;


/**
 * This subclass of ObjectInputStream delegates loading of classes to
 * an existing MLetClassLoader.
 *
 * @since 1.5
 */
class MLetObjectInputStream extends ObjectInputStream {

    private MLet loader;

    /**
     * Loader must be non-null;
     */
    public MLetObjectInputStream(InputStream in, MLet loader)
        throws IOException, StreamCorruptedException {

        super(in);
        if (loader == null) {
            throw new IllegalArgumentException("Illegal null argument to MLetObjectInputStream");
        }
        this.loader = loader;
    }

    private Class<?> primitiveType(char c) {
        switch(c) {
        case 'B':
            return Byte.TYPE;

        case 'C':
            return Character.TYPE;

        case 'D':
            return Double.TYPE;

        case 'F':
            return Float.TYPE;

        case 'I':
            return Integer.TYPE;

        case 'J':
            return Long.TYPE;

        case 'S':
            return Short.TYPE;

        case 'Z':
            return Boolean.TYPE;
        }
        return null;
    }

    /**
     * Use the given ClassLoader rather than using the system class
     */
    @Override
    protected Class<?> resolveClass(ObjectStreamClass objectstreamclass)
        throws IOException, ClassNotFoundException {

        String s = objectstreamclass.getName();
        if (s.startsWith("[")) {
            int i;
            for (i = 1; s.charAt(i) == '['; i++);
            Class<?> class1;
            if (s.charAt(i) == 'L') {
                class1 = loader.loadClass(s.substring(i + 1, s.length() - 1));
            } else {
                if (s.length() != i + 1)
                    throw new ClassNotFoundException(s);
                class1 = primitiveType(s.charAt(i));
            }
            int ai[] = new int[i];
            for (int j = 0; j < i; j++)
                ai[j] = 0;

            return Array.newInstance(class1, ai).getClass();
        } else {
            return loader.loadClass(s);
        }
    }

    /**
     * Returns the ClassLoader being used
     */
    public ClassLoader getClassLoader() {
        return loader;
    }
}

⏎ javax/management/loading/MLetObjectInputStream.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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