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/FilterWriter.java

/*
 * Copyright (c) 1996, 2005, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package java.io;


/**
 * Abstract class for writing filtered character streams.
 * The abstract class <code>FilterWriter</code> itself
 * provides default methods that pass all requests to the
 * contained stream. Subclasses of <code>FilterWriter</code>
 * should override some of these methods and may also
 * provide additional methods and fields.
 *
 * @author      Mark Reinhold
 * @since       JDK1.1
 */

public abstract class FilterWriter extends Writer {

    /**
     * The underlying character-output stream.
     */
    protected Writer out;

    /**
     * Create a new filtered writer.
     *
     * @param out  a Writer object to provide the underlying stream.
     * @throws NullPointerException if <code>out</code> is <code>null</code>
     */
    protected FilterWriter(Writer out) {
        super(out);
        this.out = out;
    }

    /**
     * Writes a single character.
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void write(int c) throws IOException {
        out.write(c);
    }

    /**
     * Writes a portion of an array of characters.
     *
     * @param  cbuf  Buffer of characters to be written
     * @param  off   Offset from which to start reading characters
     * @param  len   Number of characters to be written
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void write(char cbuf[], int off, int len) throws IOException {
        out.write(cbuf, off, len);
    }

    /**
     * Writes a portion of a string.
     *
     * @param  str  String to be written
     * @param  off  Offset from which to start reading characters
     * @param  len  Number of characters to be written
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void write(String str, int off, int len) throws IOException {
        out.write(str, off, len);
    }

    /**
     * Flushes the stream.
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void flush() throws IOException {
        out.flush();
    }

    public void close() throws IOException {
        out.close();
    }

}

⏎ java/io/FilterWriter.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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