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/nio/file/attribute/UserPrincipal.java

/*
 * Copyright (c) 2007, 2009, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.nio.file.attribute;

import java.security.Principal;

/**
 * A {@code Principal} representing an identity used to determine access rights
 * to objects in a file system.
 *
 * <p> On many platforms and file systems an entity requires appropriate access
 * rights or permissions in order to access objects in a file system. The
 * access rights are generally performed by checking the identity of the entity.
 * For example, on implementations that use Access Control Lists (ACLs) to
 * enforce privilege separation then a file in the file system may have an
 * associated ACL that determines the access rights of identities specified in
 * the ACL.
 *
 * <p> A {@code UserPrincipal} object is an abstract representation of an
 * identity. It has a {@link #getName() name} that is typically the username or
 * account name that it represents. User principal objects may be obtained using
 * a {@link UserPrincipalLookupService}, or returned by {@link
 * FileAttributeView} implementations that provide access to identity related
 * attributes. For example, the {@link AclFileAttributeView} and {@link
 * PosixFileAttributeView} provide access to a file's {@link
 * PosixFileAttributes#owner owner}.
 *
 * @since 1.7
 */

public interface UserPrincipal extends Principal { }

⏎ java/nio/file/attribute/UserPrincipal.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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