Polish Collection.toArray

Consistently use `StringUtils.toStringArray`, `ClassUtils.toClassArray`
or zero length when converting collections to arrays.

Fixes gh-12160

spring-boot-project/spring-boot-tools/spring-boot-loader/src/main/java/org/springframework/boot/loader/Launcher.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -61,7 +61,7 @@ public abstract class Launcher {
 		for (Archive archive : archives) {
 			urls.add(archive.getUrl());
 		}
-		return createClassLoader(urls.toArray(new URL[urls.size()]));
+		return createClassLoader(urls.toArray(new URL[0]));
 	}
 
 	/**