Fix checkstyle.

Author: OlgaMaciaszek

spring-cloud-openfeign-core/src/test/java/org/springframework/cloud/openfeign/encoding/Invoices.java

@@ -30,6 +30,10 @@
  */
 final class Invoices {
 
+	private Invoices() {
+		throw new IllegalStateException("Should not instantiate utility class");
+	}
+
 	public static List<Invoice> createInvoiceList(int count) {
 		final List<Invoice> invoices = new ArrayList<>();
 		for (int ind = 0; ind < count; ind++) {

spring-cloud-openfeign-core/src/test/java/org/springframework/cloud/openfeign/test/EqualsAndHashCodeAssert.java

@@ -25,7 +25,11 @@
  *
  * @author Jonatan Ivanov
  */
-public class EqualsAndHashCodeAssert {
+public final class EqualsAndHashCodeAssert {
+
+	private EqualsAndHashCodeAssert() {
+		throw new IllegalStateException("Should not instantiate utility class");
+	}
 
 	/**
 	 * Checks if equals is reflexive: for any non-null reference value x, x.equals(x)

src/checkstyle/checkstyle-suppressions.xml

@@ -13,6 +13,7 @@
 	<suppress files=".*ProtobufTest.*" checks="LineLengthCheck" />
 	<suppress files=".*Hello.*" checks="RedundantModifier"/>
 	<suppress files=".*test.*" checks="JavadocStyle"/>
+	<suppress files=".*test.*" checks="JavadocVariable"/>
 	<!-- Important -->
 	<suppress files=".*HttpEncoding.*" checks="InterfaceIsTypeCheck" />
 </suppressions>