Use hasSize() where possible

See gh-24172

spring-web/src/test/java/org/springframework/web/accept/MappingMediaTypeFileExtensionResolverTests.java

@@ -41,7 +41,7 @@ public class MappingMediaTypeFileExtensionResolverTests {
 	public void resolveExtensions() {
 		List<String> extensions = this.resolver.resolveFileExtensions(MediaType.APPLICATION_JSON);
 
-		assertThat(extensions).size().isEqualTo(1);
+		assertThat(extensions).hasSize(1);
 		assertThat(extensions.get(0)).isEqualTo("json");
 	}