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 com.* package in JRE 1.8.0_191 rt.jar. Java source codes are also provided.

⏎ com/sun/imageio/plugins/common/InputStreamAdapter.java

/*
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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package com.sun.imageio.plugins.common;

import java.io.IOException;
import java.io.InputStream;
import javax.imageio.stream.ImageInputStream;

public class InputStreamAdapter extends InputStream {

    ImageInputStream stream;

    public InputStreamAdapter(ImageInputStream stream) {
        super();

        this.stream = stream;
    }

    public int read() throws IOException {
        return stream.read();
    }

    public int read(byte b[], int off, int len) throws IOException {
        return stream.read(b, off, len);
    }
}

⏎ com/sun/imageio/plugins/common/InputStreamAdapter.java

Or download all of them as a single archive file:

File name: jre-rt-com-1.8.0_191-src.zip
File size: 8099783 bytes
Release date: 2018-10-28
Download 

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