Summary

Add a new lint option, missing-explicit-ctor, to javac to warn about reliance on a default constructor in a class that is part of a formal API.

Problem

While convenient for informal classes, default constructors in formal API classes will not have javadoc and may be unintended and unwanted.

Solution

Warn about reliance on a default constructor on classes where there is some likelihood of it being a problem, name public classes in a named package that has an unqualified export from its module. In addition, for nested classes, all the syntactically enclosing classes must be public too.

Specification

New text displayed as a key for javac's -Xlint:

     missing-explicit-ctor Warn about missing explicit constructors in public classes in exported packages.