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/security/spec/DSAPrivateKeySpec.java

/*
 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package java.security.spec;

import java.math.BigInteger;

/**
 * This class specifies a DSA private key with its associated parameters.
 *
 * @author Jan Luehe
 *
 *
 * @see java.security.Key
 * @see java.security.KeyFactory
 * @see KeySpec
 * @see DSAPublicKeySpec
 * @see PKCS8EncodedKeySpec
 *
 * @since 1.2
 */

public class DSAPrivateKeySpec implements KeySpec {

    private BigInteger x;
    private BigInteger p;
    private BigInteger q;
    private BigInteger g;

    /**
     * Creates a new DSAPrivateKeySpec with the specified parameter values.
     *
     * @param x the private key.
     *
     * @param p the prime.
     *
     * @param q the sub-prime.
     *
     * @param g the base.
     */
    public DSAPrivateKeySpec(BigInteger x, BigInteger p, BigInteger q,
                             BigInteger g) {
        this.x = x;
        this.p = p;
        this.q = q;
        this.g = g;
    }

    /**
     * Returns the private key {@code x}.
     *
     * @return the private key {@code x}.
     */
    public BigInteger getX() {
        return this.x;
    }

    /**
     * Returns the prime {@code p}.
     *
     * @return the prime {@code p}.
     */
    public BigInteger getP() {
        return this.p;
    }

    /**
     * Returns the sub-prime {@code q}.
     *
     * @return the sub-prime {@code q}.
     */
    public BigInteger getQ() {
        return this.q;
    }

    /**
     * Returns the base {@code g}.
     *
     * @return the base {@code g}.
     */
    public BigInteger getG() {
        return this.g;
    }
}

⏎ java/security/spec/DSAPrivateKeySpec.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
Download 

⇒ JRE 8 rt.jar - javax.* Package Source Code

⇐ JRE 8 plugin.jar - Java Deploy Control Panel Plugin

⇑ Download and Use JDK 8

⇑⇑ FAQ for JDK (Java Development Kit)