Apache Ant Source Code Files are inside the Apache Ant source package file like apache-ant-1.10.10-src.zip. Unzip the source package file and go to the "src/main" sub-directory, you will see source code files.

Here is the list of Java source code files of the Apache Ant 1.10.10 in \Users\fyicenter\apache-ant-1.10.10\src\main:

⏎ org/apache/tools/zip/ZipConstants.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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
 *
 *      https://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 org.apache.tools.zip;

/**
 * Various constants used throughout the package.
 */
final class ZipConstants {
    private ZipConstants() { }

    /** Masks last eight bits */
    static final int BYTE_MASK = 0xFF;

    /** length of a ZipShort in bytes */
    static final int SHORT = 2;

    /** length of a ZipLong in bytes */
    static final int WORD = 4;

    /** length of a ZipEightByteInteger in bytes */
    static final int DWORD = 8;

    /** Initial ZIP specification version */
    static final int INITIAL_VERSION = 10;

    /** ZIP specification version that introduced data descriptor method */
    static final int DATA_DESCRIPTOR_MIN_VERSION = 20;

    /** ZIP specification version that introduced ZIP64 */
    static final int ZIP64_MIN_VERSION = 45;

    /**
     * Value stored in two-byte size and similar fields if ZIP64
     * extensions are used.
     */
    static final int ZIP64_MAGIC_SHORT = 0xFFFF;

    /**
     * Value stored in four-byte size and similar fields if ZIP64
     * extensions are used.
     */
    static final long ZIP64_MAGIC = 0xFFFFFFFFL;

}

⏎ org/apache/tools/zip/ZipConstants.java

Or download all of them as a single archive file:

File name: apache-ant-1.10.10-fyi.zip
File size: 2392938 bytes
Release date: 2021-04-17
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