better form

src/main/java/com/zipcoder/payment/PaymentPresenter.java

 }
 
     public String toStringByPayerName(Payment[] payments){
+
         StringBuilder output = new StringBuilder();
         Arrays.sort(payments,new PaymentSortByPayer());
         for (int i=0; i<payments.length; i++) {
 
     public String toStringById(Payment[] payments){
         StringBuilder output = new StringBuilder();
-        Arrays.sort(payments,(p, q) -> p.getId().compareTo(q.getId()));
+        Arrays.sort(payments, Comparator.comparing(Payment::getId));
 
         for (int i=0; i<payments.length; i++) {
             output.append(payments[i].getShortDescription()+"\n");

src/main/java/com/zipcoder/payment/Paypal.java

 
     }
 
+    public Paypal(){}
+
     public void setId(Long id) {
         this.id = id;
     }

src/test/java/com/zipcoder/payment/PaymentPresenterTest.java

     String actual = presenter.toStringById(payments);
 
     Assert.assertEquals(expected, actual);
-}
+
+    }
+
+
 }