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/script/Compilable.java

/*
 * Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package javax.script;

import java.util.Map;
import java.io.Reader;

/**
 * The optional interface implemented by ScriptEngines whose methods compile scripts
 * to a form that can be executed repeatedly without recompilation.
 *
 * @author Mike Grogan
 * @since 1.6
 */
public interface Compilable {
    /**
     * Compiles the script (source represented as a <code>String</code>) for
     * later execution.
     *
     * @param script The source of the script, represented as a <code>String</code>.
     *
     * @return An instance of a subclass of <code>CompiledScript</code> to be executed later using one
     * of the <code>eval</code> methods of <code>CompiledScript</code>.
     *
     * @throws ScriptException if compilation fails.
     * @throws NullPointerException if the argument is null.
     *
     */

    public CompiledScript compile(String script) throws
            ScriptException;

    /**
     * Compiles the script (source read from <code>Reader</code>) for
     * later execution.  Functionality is identical to
     * <code>compile(String)</code> other than the way in which the source is
     * passed.
     *
     * @param script The reader from which the script source is obtained.
     *
     * @return An instance of a subclass of <code>CompiledScript</code> to be executed
     * later using one of its <code>eval</code> methods of <code>CompiledScript</code>.
     *
     * @throws ScriptException if compilation fails.
     * @throws NullPointerException if argument is null.
     */
    public CompiledScript compile(Reader script) throws
            ScriptException;
}

⏎ javax/script/Compilable.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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