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 java.* package in JRE 1.8.0_191 rt.jar. Java source codes are also provided.

⏎ java/awt/geom/Dimension2D.java

/*
 * Copyright (c) 1997, 2011, 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 java.awt.geom;

/**
 * The <code>Dimension2D</code> class is to encapsulate a width
 * and a height dimension.
 * <p>
 * This class is only the abstract superclass for all objects that
 * store a 2D dimension.
 * The actual storage representation of the sizes is left to
 * the subclass.
 *
 * @author      Jim Graham
 * @since 1.2
 */
public abstract class Dimension2D implements Cloneable {

    /**
     * This is an abstract class that cannot be instantiated directly.
     * Type-specific implementation subclasses are available for
     * instantiation and provide a number of formats for storing
     * the information necessary to satisfy the various accessor
     * methods below.
     *
     * @see java.awt.Dimension
     * @since 1.2
     */
    protected Dimension2D() {
    }

    /**
     * Returns the width of this <code>Dimension</code> in double
     * precision.
     * @return the width of this <code>Dimension</code>.
     * @since 1.2
     */
    public abstract double getWidth();

    /**
     * Returns the height of this <code>Dimension</code> in double
     * precision.
     * @return the height of this <code>Dimension</code>.
     * @since 1.2
     */
    public abstract double getHeight();

    /**
     * Sets the size of this <code>Dimension</code> object to the
     * specified width and height.
     * This method is included for completeness, to parallel the
     * {@link java.awt.Component#getSize getSize} method of
     * {@link java.awt.Component}.
     * @param width  the new width for the <code>Dimension</code>
     * object
     * @param height  the new height for the <code>Dimension</code>
     * object
     * @since 1.2
     */
    public abstract void setSize(double width, double height);

    /**
     * Sets the size of this <code>Dimension2D</code> object to
     * match the specified size.
     * This method is included for completeness, to parallel the
     * <code>getSize</code> method of <code>Component</code>.
     * @param d  the new size for the <code>Dimension2D</code>
     * object
     * @since 1.2
     */
    public void setSize(Dimension2D d) {
        setSize(d.getWidth(), d.getHeight());
    }

    /**
     * Creates a new object of the same class as this object.
     *
     * @return     a clone of this instance.
     * @exception  OutOfMemoryError            if there is not enough memory.
     * @see        java.lang.Cloneable
     * @since      1.2
     */
    public Object clone() {
        try {
            return super.clone();
        } catch (CloneNotSupportedException e) {
            // this shouldn't happen, since we are Cloneable
            throw new InternalError(e);
        }
    }
}

⏎ java/awt/geom/Dimension2D.java

Or download all of them as a single archive file:

File name: jre-rt-java-1.8.0_191-src.zip
File size: 6664831 bytes
Release date: 2018-10-28
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