java.lang.AbstractMethodError in widget subclasses

Description

Since java-client 8.6.0 calling the implementation of abstract methods in widget subclasses results in throwing exception java.lang.AbstractMethodError.

Environment

• Java-client 8.6.0
• Appium 2.1.3
• Java 11

Code To Reproduce Issue [ Good To Have ]

Widgets:

public abstract class Tab extends Widget {

    protected Tab(WebElement element) {
        super(element);
    }

    public abstract boolean isSelected();
}

public class AndroidTab extends Tab {

    protected AndroidTab(WebElement element) {
        super(element);
    }

    @Override
    public boolean isSelected() {
        return getWrappedElement().isSelected();
    }
}

Screen:

@AndroidFindBy(id = "loginTab")
@OverrideWidget(androidUIAutomator = AndroidTab.class, iOSXCUITAutomation = IosTab.class)
private Tab loginTab;

public boolean isLoginTabSelected() {
    return loginTab.isSelected();
}

Exception Stacktraces

java.lang.AbstractMethodError: Receiver class autotests.component.tab.Tab$ByteBuddy$WYq3RqHe does not define or inherit an implementation of the resolved method 'abstract boolean isSelected()' of abstract class autotests.component.tab.Tab.
at autotests.screen.authorization.LoginScreen.isLoginTabSelected

Start with the Tab and AndroidTab reproducer and trace how the Appium Java client creates widget subclasses for @OverrideWidget. Investigate the generated Tab$ByteBuddy class and the isSelected() call, then reproduce the failure with the Java 11, Appium 2.1.3, and java-client 8.6.0 environment. Done means abstract methods in widget subclasses no longer produce AbstractMethodError.