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/type/TypeVariable.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.type;


import javax.lang.model.element.Element;
import javax.lang.model.element.TypeParameterElement;
import javax.lang.model.util.Types;


/**
 * Represents a type variable.
 * A type variable may be explicitly declared by a
 * {@linkplain TypeParameterElement type parameter} of a
 * type, method, or constructor.
 * A type variable may also be declared implicitly, as by
 * the capture conversion of a wildcard type argument
 * (see chapter 5 of
 * <cite>The Java&trade; Language Specification</cite>).
 *
 * @author Joseph D. Darcy
 * @author Scott Seligman
 * @author Peter von der Ah&eacute;
 * @see TypeParameterElement
 * @since 1.6
 */
public interface TypeVariable extends ReferenceType {

    /**
     * Returns the element corresponding to this type variable.
     *
     * @return the element corresponding to this type variable
     */
    Element asElement();

    /**
     * Returns the upper bound of this type variable.
     *
     * <p> If this type variable was declared with no explicit
     * upper bounds, the result is {@code java.lang.Object}.
     * If it was declared with multiple upper bounds,
     * the result is an {@linkplain IntersectionType intersection type};
     * individual bounds can be found by examining the result's
     * {@linkplain IntersectionType#getBounds() bounds}.
     *
     * @return the upper bound of this type variable
     */
    TypeMirror getUpperBound();

    /**
     * Returns the lower bound of this type variable.  While a type
     * parameter cannot include an explicit lower bound declaration,
     * capture conversion can produce a type variable with a
     * non-trivial lower bound.  Type variables otherwise have a
     * lower bound of {@link NullType}.
     *
     * @return the lower bound of this type variable
     */
    TypeMirror getLowerBound();
}

⏎ javax/lang/model/type/TypeVariable.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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