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/io/FileReader.java

/*
 * Copyright (c) 1996, 2001, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package java.io;


/**
 * Convenience class for reading character files.  The constructors of this
 * class assume that the default character encoding and the default byte-buffer
 * size are appropriate.  To specify these values yourself, construct an
 * InputStreamReader on a FileInputStream.
 *
 * <p><code>FileReader</code> is meant for reading streams of characters.
 * For reading streams of raw bytes, consider using a
 * <code>FileInputStream</code>.
 *
 * @see InputStreamReader
 * @see FileInputStream
 *
 * @author      Mark Reinhold
 * @since       JDK1.1
 */
public class FileReader extends InputStreamReader {

   /**
    * Creates a new <tt>FileReader</tt>, given the name of the
    * file to read from.
    *
    * @param fileName the name of the file to read from
    * @exception  FileNotFoundException  if the named file does not exist,
    *                   is a directory rather than a regular file,
    *                   or for some other reason cannot be opened for
    *                   reading.
    */
    public FileReader(String fileName) throws FileNotFoundException {
        super(new FileInputStream(fileName));
    }

   /**
    * Creates a new <tt>FileReader</tt>, given the <tt>File</tt>
    * to read from.
    *
    * @param file the <tt>File</tt> to read from
    * @exception  FileNotFoundException  if the file does not exist,
    *                   is a directory rather than a regular file,
    *                   or for some other reason cannot be opened for
    *                   reading.
    */
    public FileReader(File file) throws FileNotFoundException {
        super(new FileInputStream(file));
    }

   /**
    * Creates a new <tt>FileReader</tt>, given the
    * <tt>FileDescriptor</tt> to read from.
    *
    * @param fd the FileDescriptor to read from
    */
    public FileReader(FileDescriptor fd) {
        super(new FileInputStream(fd));
    }

}

⏎ java/io/FileReader.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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