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/org/apache/xerces/internal/impl/dv/xs/Base64BinaryDV.java

/*
 * Copyright (c) 2007, 2018, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 2001, 2002,2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.sun.org.apache.xerces.internal.impl.dv.xs;

import com.sun.org.apache.xerces.internal.impl.dv.InvalidDatatypeValueException;
import com.sun.org.apache.xerces.internal.impl.dv.ValidationContext;
import com.sun.org.apache.xerces.internal.impl.dv.util.Base64;
import com.sun.org.apache.xerces.internal.impl.dv.util.ByteListImpl;

/**
 * Represent the schema type "base64Binary"
 *
 * @xerces.internal
 *
 * @author Neeraj Bajaj, Sun Microsystems, inc.
 * @author Sandy Gao, IBM
 *
 * @version $Id: Base64BinaryDV.java,v 1.7 2010-11-01 04:39:46 joehw Exp $
 */
public class Base64BinaryDV extends TypeValidator {

    public short getAllowedFacets(){
        return (XSSimpleTypeDecl.FACET_LENGTH | XSSimpleTypeDecl.FACET_MINLENGTH | XSSimpleTypeDecl.FACET_MAXLENGTH | XSSimpleTypeDecl.FACET_PATTERN | XSSimpleTypeDecl.FACET_ENUMERATION | XSSimpleTypeDecl.FACET_WHITESPACE );
    }

    public Object getActualValue(String content, ValidationContext context) throws InvalidDatatypeValueException {
        byte[] decoded = Base64.decode(content);
        if (decoded == null)
            throw new InvalidDatatypeValueException("cvc-datatype-valid.1.2.1", new Object[]{content, "base64Binary"});

        return new XBase64(decoded);
    }

    // length of a binary type is the number of bytes
    public int getDataLength(Object value) {
        return ((XBase64)value).getLength();
    }

    /**
     * represent base64 data
     */
    private static final class XBase64 extends ByteListImpl {

        public XBase64(byte[] data) {
            super(data);
        }
        public synchronized String toString() {
            if (canonical == null) {
                canonical = Base64.encode(data);
            }
            return canonical;
        }

        public boolean equals(Object obj) {
            if (!(obj instanceof XBase64))
                return false;
            byte[] odata = ((XBase64)obj).data;
            int len = data.length;
            if (len != odata.length)
                return false;
            for (int i = 0; i < len; i++) {
                if (data[i] != odata[i])
                    return false;
            }
            return true;
        }

        public int hashCode() {
            int hash = 0;
            for (int i = 0; i < data.length; ++i) {
                hash = hash * 37 + (((int) data[i]) & 0xff);
            }
            return hash;
        }
    }
} // class Base64BinaryDV

⏎ com/sun/org/apache/xerces/internal/impl/dv/xs/Base64BinaryDV.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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