checker/tests/nullness/LubTest.java

import org.checkerframework.checker.nullness.qual.*;

public class LubTest {

  @Nullable String str;

  public void setStr(@Nullable String text) {
    str = text;
  }

  public @Nullable String getStr() {
    return str;
  }

  public void ok(@Nullable LubTest t) {
    if (t == null) {
      this.setStr("");
    } else {
      this.setStr(t.getStr());
    }
  }

  public void notok(@Nullable LubTest t) {
    this.setStr((t == null) ? "" : t.getStr());
  }
}