JDK 11 jdk.jartool.jmod is the JMOD file for JDK 11 JAR tool, which can be invoked by the "jar" command.

JDK 11 JAR tool compiled class files are stored in \fyicenter\jdk-11.0.1\jmods\jdk.jartool.jmod.

JDK 11 JAR tool compiled class files are also linked and stored in the \fyicenter\jdk-11.0.1\lib\modules JImage file.

JDK 11 JAR tool source code files are stored in \fyicenter\jdk-11.0.1\lib\src.zip\jdk.jartool.

You can click and view the content of each source code file in the list below.

⏎ sun/tools/jar/JarToolProvider.java

/*
 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package sun.tools.jar;

import java.io.PrintWriter;
import java.util.spi.ToolProvider;

public class JarToolProvider implements ToolProvider {
    public String name() {
        return "jar";
    }

    public int run(PrintWriter out, PrintWriter err, String... args) {
        boolean ok = new Main(out, err, name()).run(args);
        return ok ? 0 : 1;
    }
}

⏎ sun/tools/jar/JarToolProvider.java

Or download all of them as a single archive file:

File name: jdk.jartool-11.0.1-src.zip
File size: 101994 bytes
Release date: 2018-11-04
Download 

⇒ JDK 11 jdk.javadoc.jmod - Java Document Tool

⇐ JDK 11 jdk.internal.vm.compiler.management.jmod - Internal VM Compiler Management Module

⇑ Download and Use JDK 11

⇑⇑ FAQ for JDK (Java Development Kit)