checker/tests/nullness/FlowCompoundConcatenation.java

public class FlowCompoundConcatenation {
  static String getNonNullString() {
    return "";
  }

  public static void testCompoundAssignWithNullAndMethodCall() {
    String s = null;
    s += getNonNullString();
    s.toString();
  }

  public static void testCompoundAssignWithNull() {
    String s = null;
    s += "hello";
    s.toString();
  }
}