Public constructor on an abstract class

_[Original issue](https://code.google.com/p/error-prone/issues/detail?id=134) created by **dovwas@google.com** on 2013-06-05 at 02:25 PM_

---

A constructor on an abstract class should be declared as protected, there is never a need to declare it as public, since only subclasses can actually invoke it. There is, admittedly, not much negative consequence for this error, but I feel it is always a mistake, and one I'd be happy to see my compiler warn me about.
# Positive case:

public abstract class AbstractReport {

  public AbstractReport(String reportName) {
    // ...
  }

  public abstract void runReport();

}
# Negative case:

public abstract class AbstractReport {

  protected AbstractReport(String reportName) {
    // ...
  }

  public abstract void runReport();

}