Using internal sun classes with javac

Is there a way to disable restrictions of javac 1.6.0_22 that prevent me from using JRE internal classes like sun.awt.event.* ?

I'm not looking for:

1. an explanation why it is forbidden.
2. suggestion to use different classes
3. suggestion to use reflection
4. suggestion to use ecj/eclipse

I just want to know if it is possible or not, and if it is then how.

I have found the answer myself.

When javac is compiling code it doesn't link against rt.jar by default. Instead it uses special symbol file lib/ct.sym with class stubs.

Surprisingly this file contains many but not all of internal sun classes. In my case one of those more-internal-than-usual classes was sun.awt.event.IgnorePaintEvent.

And the answer to my question is: javac -XDignore.symbol.file

That's what javac uses for compiling rt.jar.

In addition to the answer by @marcin-wisnicki if you're using Maven, note that the compiler plugin will silently drop any -XD flags, unless you also specify <fork>true</fork>: e.g.

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.3</version>
            <configuration>
                <source>1.7</source>
                <target>1.7</target>
                <compilerArgs>
                    <arg>-XDignore.symbol.file</arg>
                </compilerArgs>
                <fork>true</fork>
            </configuration>
            ...

There's a better solution. First add the option to javac -XDenableSunApiLintControl and then use @SupressWarnings("sunapi") in your code.

Normally, this only produces a Warning message; e.g.

[javac] /media/disk/opensso2/opensso/products/federation/openfm/source/com/sun/identity/wss/xmlsig/WSSSignatureProvider.java:46: warning: com.sun.org.apache.xpath.internal.XPathAPI is Sun proprietary API and may be removed in a future release
[javac] import com.sun.org.apache.xpath.internal.XPathAPI;

Perhaps you have told the Java compiler to treat warnings as errors.

If you are using Gradle, you need to use these options

compileJava {
    // enable using internal libraries
    options.fork = true
    options.forkOptions.executable = 'javac'
    options.compilerArgs << '-XDignore.symbol.file' }

Another way is change jdk.

In my case project java version 1.8. I used from jdk 11. Therefore This error has found in my project. So I changed my jdk from 11 to 1.8. It has worked for me.