Is there a java lambda expression equivalent of the C# linq let?

Question

Is there a java 8 lambda expression equivalent of the let setting? For instance, how would I write this c# linq expression using Java 8 lambda expressions? ``` String[] lines = new String[]{"Porky.Pig", "Darth.Vader", "Donald.Duck", "George Lucas"}; (from l in lines let p = l.IndexOf('.') where p >= 0 select new { FirstName = l.Substring(0, p), LastName = l.Substring(p + 1) }).Dump(); ``` I want to evaluate l.IndexOf('.') only once. The closest I came up with is: ``` String[] lines = new String[]{"Porky.Pig", "Darth.Vader", "Donald.Duck", "George Lucas"}; Arrays.stream(lines) .filter(x -> x.indexOf('.') > 0) .map(x -> { int p = x.indexOf('.'); return new Person (x.substring(0, p), x.substring( p + 1)); }); ``` where: ``` public class Person { public Person(String firstName, String lastName) { } } ``` ok, based on the suggestion in the Shlomi Borovitz's answer I came up with this which makes use of this Pair class ``` String[] lines = new String[]{"Porky.Pig", "Darth.Vader", "Donald.Du…

Accepted Answer

The linq query in C# is converted to "dot syntaxt" (which is regular method calls): The query:

```
from l in lines      
let p = l.IndexOf('.')
where p >= 0
select new 
{
    FirstName = l.Substring(0, p), 
    LastName = l.Substring(p + 1)
}
```

is converted to something like this:

```
lines.Select(l => new {l, p = l.IndexOf('.') })
     .Where(_ => _.p >= 0)
     .Select(_ => new 
         { 
             FirstName = _.l.SubString(0, _.p), 
             LastName = _.l.SubString(_.p + 1) 
         })
```

Figure out how to do that in Java.

If there is no equivalent to C#'s anonymous types, tuples are a good idea, where the usage isn't justifying creating another class.

Is there a java lambda expression equivalent of the C# linq let?

Solution

Problem