Replace string

During the Java compilation performance the JDK does improvements with String, this way, these may be replaced with java.lang.String expressions which results in simpler and possibly more efficient code.
I'm not sure about these changes. The following

```java
// code
"str1" + var + "str2"
```
will compile to
```java
// compiled
new StringBuilder("str1").append(var).append("str2")
```
which is a bit more efficient than what we're currently doing for example in ClasspathUtils, where we initialize the StringBuilder without constructor arguments:
```java
// code
new StringBuilder().append("str1").append(var).append("str2")
```
But in StringUtils and Range, we're passing an initial length to the StringBuilder. I don't know what are the implications of the proposed change in these areas of the code.