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/X509EncodedKeySpec.java

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

/**
 * This class represents the ASN.1 encoding of a public key,
 * encoded according to the ASN.1 type {@code SubjectPublicKeyInfo}.
 * The {@code SubjectPublicKeyInfo} syntax is defined in the X.509
 * standard as follows:
 *
 * <pre>
 * SubjectPublicKeyInfo ::= SEQUENCE {
 *   algorithm AlgorithmIdentifier,
 *   subjectPublicKey BIT STRING }
 * </pre>
 *
 * @author Jan Luehe
 *
 *
 * @see java.security.Key
 * @see java.security.KeyFactory
 * @see KeySpec
 * @see EncodedKeySpec
 * @see PKCS8EncodedKeySpec
 *
 * @since 1.2
 */

public class X509EncodedKeySpec extends EncodedKeySpec {

    /**
     * Creates a new X509EncodedKeySpec with the given encoded key.
     *
     * @param encodedKey the key, which is assumed to be
     * encoded according to the X.509 standard. The contents of the
     * array are copied to protect against subsequent modification.
     * @exception NullPointerException if {@code encodedKey}
     * is null.
     */
    public X509EncodedKeySpec(byte[] encodedKey) {
        super(encodedKey);
    }

    /**
     * Returns the key bytes, encoded according to the X.509 standard.
     *
     * @return the X.509 encoding of the key. Returns a new array
     * each time this method is called.
     */
    public byte[] getEncoded() {
        return super.getEncoded();
    }

    /**
     * Returns the name of the encoding format associated with this
     * key specification.
     *
     * @return the string {@code "X.509"}.
     */
    public final String getFormat() {
        return "X.509";
    }
}

⏎ java/security/spec/X509EncodedKeySpec.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 

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