Question: Strings are immutable, does it mean that i always have to do something like that with a string passed to a method?

```
str= str.toLowerCase();

```

or is 

```
str.toLowerCase();

```

fine? I tried the second one and it doesn't give me any errors, why?

Answer: 
The first one is how you do it.
`str.toLowerCase();` on it's own wont do anything. The method returns a values so you should use that value in an assignment or condition.