refactor(phonenumberverification): align token constructor pre-conditions checks with idiomatic checkNotNull patterns

Author: lahirumaramba

src/main/java/com/google/firebase/phonenumberverification/FirebasePhoneNumberVerificationToken.java

@@ -17,6 +17,7 @@
 package com.google.firebase.phonenumberverification;
 
 import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
@@ -35,8 +36,8 @@ public class FirebasePhoneNumberVerificationToken {
    * @param claims A map of JWT claims.
    */
   public FirebasePhoneNumberVerificationToken(Map<String, Object> claims) {
-    checkArgument(claims != null && claims.containsKey("sub"),
-        "Claims map must at least contain sub");
+    checkNotNull(claims, "Claims map must not be null");
+    checkArgument(claims.containsKey("sub"), "Claims map must contain sub");
     this.claims = ImmutableMap.copyOf(claims);
   }
 

src/main/java/com/google/firebase/phonenumberverification/internal/FirebasePhoneNumberVerificationTokenVerifier.java

@@ -42,7 +42,6 @@
 import java.net.MalformedURLException;
 import java.net.URI;
 import java.text.ParseException;
-import java.util.Objects;
 
 /**
  * Internal class to verify Firebase Phone Number Verification tokens.

src/test/java/com/google/firebase/phonenumberverification/FirebasePhoneNumberVerificationTokenTest.java

@@ -91,14 +91,14 @@ public void test_No_Sub() {
     IllegalArgumentException e = assertThrows(IllegalArgumentException.class, () ->
         new FirebasePhoneNumberVerificationToken(claims)
     );
-    assertTrue(e.getMessage().contains("Claims map must at least contain sub"));
+    assertTrue(e.getMessage().contains("Claims map must contain sub"));
   }
 
   @Test
   public void test_Null_Sub() {
-    IllegalArgumentException e = assertThrows(IllegalArgumentException.class, () ->
+    NullPointerException e = assertThrows(NullPointerException.class, () ->
         new FirebasePhoneNumberVerificationToken(null)
     );
-    assertTrue(e.getMessage().contains("Claims map must at least contain sub"));
+    assertEquals("Claims map must not be null", e.getMessage());
   }
 }