import java.io.*;
import org.checkerframework.checker.nullness.qual.*;
import org.checkerframework.checker.nullness.qual.EnsuresNonNull;

public class FlowNonThis {

  @Nullable String c;

  public static void main(String[] args) {
    FlowNonThis t = new FlowNonThis();
    t.setup();
    System.out.println(t.c.length());
    t.erase();
    // :: error: (dereference.of.nullable)
    System.out.println(t.c.length());
  }

  public void setupThenErase() {
    setup();
    System.out.println(c.length());
    erase();
    // :: error: (dereference.of.nullable)
    System.out.println(c.length());
  }

  public void justErase() {
    // :: error: (dereference.of.nullable)
    System.out.println(c.length());
    erase();
    // :: error: (dereference.of.nullable)
    System.out.println(c.length());
  }

  @EnsuresNonNull("c")
  public void setup() {
    c = "setup";
  }

  public void erase() {
    c = null;
  }
}