oops I added lambdas

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

 package com.zipcoder.payment;
 
 import java.util.Arrays;
+import java.util.Comparator;
 
 public class PaymentPresenter {
 
+    Comparator<Payment> paymentSortByID = (Payment p1, Payment p2)  -> {
+            Long p1ID = p1.getId();
+            Long p2ID = p2.getId();
+            return p1ID.compareTo(p2ID);
+    };
+
 
     public String toString(Payment[] p){
         Arrays.sort(p);
     }
 
     public String toStringByID(Payment[] p){
-        PaymentSortById psbi = new PaymentSortById();
-        Arrays.sort(p, psbi);
+        Arrays.sort(p, paymentSortByID);
         return generateOutputString(p);
     }
 

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

-package com.zipcoder.payment;
-
-import java.util.Comparator;
-
-public class PaymentSortById implements Comparator<Payment>{
-    public int compare(Payment p1, Payment p2) {
-        Long p1ID = p1.getId();
-        Long p2ID = p2.getId();
-        return p1ID.compareTo(p2ID);
-    }
-
-}

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

-package com.zipcoder.payment;
-
-import org.junit.Assert;
-import org.junit.Test;
-
-public class PaymentSortByIdTest {
-    Check ch = new Check(1, "Sansa Stark", "1234567", "987654321");
-    PayPal pp = new PayPal(1, "Catelyn Stark", "ladystark@winterfell.com");
-    CreditCard cc = new CreditCard(123, "Robb Stark", "4444444444", 12, 2020);
-    Check ch2 = new Check(900, "Arya Stark", "1234569", "987654444");
-
-    PaymentSortById psbi = new PaymentSortById();
-
-
-    @Test
-    public void paymentSortByIdTest1() {
-        int expected = 0;
-        int actual = psbi.compare(ch, pp);
-        Assert.assertEquals(expected, actual);
-    }
-    @Test
-    public void paymentSortByIdTest2() {
-        int actual = psbi.compare(ch, cc);
-        Assert.assertTrue(actual < 0);
-    }
-    @Test
-    public void paymentSortByIdTest3() {
-        int actual = psbi.compare(ch2, cc);
-        Assert.assertTrue(actual > 0);
-    }
-}