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/lang/EnumConstantNotPresentException.java

/*
 * Copyright (c) 2004, 2011, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package java.lang;

/**
 * Thrown when an application tries to access an enum constant by name
 * and the enum type contains no constant with the specified name.
 * This exception can be thrown by the {@linkplain
 * java.lang.reflect.AnnotatedElement API used to read annotations
 * reflectively}.
 *
 * @author  Josh Bloch
 * @see     java.lang.reflect.AnnotatedElement
 * @since   1.5
 */
@SuppressWarnings("rawtypes") /* rawtypes are part of the public api */
public class EnumConstantNotPresentException extends RuntimeException {
    private static final long serialVersionUID = -6046998521960521108L;

    /**
     * The type of the missing enum constant.
     */
    private Class<? extends Enum> enumType;

    /**
     * The name of the missing enum constant.
     */
    private String constantName;

    /**
     * Constructs an <tt>EnumConstantNotPresentException</tt> for the
     * specified constant.
     *
     * @param enumType the type of the missing enum constant
     * @param constantName the name of the missing enum constant
     */
    public EnumConstantNotPresentException(Class<? extends Enum> enumType,
                                           String constantName) {
        super(enumType.getName() + "." + constantName);
        this.enumType = enumType;
        this.constantName  = constantName;
    }

    /**
     * Returns the type of the missing enum constant.
     *
     * @return the type of the missing enum constant
     */
    public Class<? extends Enum> enumType() { return enumType; }

    /**
     * Returns the name of the missing enum constant.
     *
     * @return the name of the missing enum constant
     */
    public String constantName() { return constantName; }
}

⏎ java/lang/EnumConstantNotPresentException.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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