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/lang/model/element/ExecutableElement.java

/*
 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package javax.lang.model.element;

import java.util.List;
import javax.lang.model.type.*;

/**
 * Represents a method, constructor, or initializer (static or
 * instance) of a class or interface, including annotation type
 * elements.
 *
 * @author Joseph D. Darcy
 * @author Scott Seligman
 * @author Peter von der Ahé
 * @see ExecutableType
 * @since 1.6
 */
public interface ExecutableElement extends Element, Parameterizable {
    /**
     * Returns the formal type parameters of this executable
     * in declaration order.
     *
     * @return the formal type parameters, or an empty list
     * if there are none
     */
    List<? extends TypeParameterElement> getTypeParameters();

    /**
     * Returns the return type of this executable.
     * Returns a {@link NoType} with kind {@link TypeKind#VOID VOID}
     * if this executable is not a method, or is a method that does not
     * return a value.
     *
     * @return the return type of this executable
     */
    TypeMirror getReturnType();

    /**
     * Returns the formal parameters of this executable.
     * They are returned in declaration order.
     *
     * @return the formal parameters,
     * or an empty list if there are none
     */
    List<? extends VariableElement> getParameters();

    /**
     * Returns the receiver type of this executable,
     * or {@link javax.lang.model.type.NoType NoType} with
     * kind {@link javax.lang.model.type.TypeKind#NONE NONE}
     * if the executable has no receiver type.
     *
     * An executable which is an instance method, or a constructor of an
     * inner class, has a receiver type derived from the {@linkplain
     * #getEnclosingElement declaring type}.
     *
     * An executable which is a static method, or a constructor of a
     * non-inner class, or an initializer (static or instance), has no
     * receiver type.
     *
     * @return the receiver type of this executable
     * @since 1.8
     */
    TypeMirror getReceiverType();

    /**
     * Returns {@code true} if this method or constructor accepts a variable
     * number of arguments and returns {@code false} otherwise.
     *
     * @return {@code true} if this method or constructor accepts a variable
     * number of arguments and {@code false} otherwise
     */
    boolean isVarArgs();

    /**
     * Returns {@code true} if this method is a default method and
     * returns {@code false} otherwise.
     *
     * @return {@code true} if this method is a default method and
     * {@code false} otherwise
     * @since 1.8
     */
    boolean isDefault();

    /**
     * Returns the exceptions and other throwables listed in this
     * method or constructor's {@code throws} clause in declaration
     * order.
     *
     * @return the exceptions and other throwables listed in the
     * {@code throws} clause, or an empty list if there are none
     */
    List<? extends TypeMirror> getThrownTypes();

    /**
     * Returns the default value if this executable is an annotation
     * type element.  Returns {@code null} if this method is not an
     * annotation type element, or if it is an annotation type element
     * with no default value.
     *
     * @return the default value, or {@code null} if none
     */
    AnnotationValue getDefaultValue();

    /**
     * Returns the simple name of a constructor, method, or
     * initializer.  For a constructor, the name {@code "<init>"} is
     * returned, for a static initializer, the name {@code "<clinit>"}
     * is returned, and for an anonymous class or instance
     * initializer, an empty name is returned.
     *
     * @return the simple name of a constructor, method, or
     * initializer
     */
    @Override
    Name getSimpleName();
}

⏎ javax/lang/model/element/ExecutableElement.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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