Razib Razib - 1 month ago 9
Java Question

Storing variable in while using lambda expression

I am working with

java-8
. Please see the following code snippet -

studentsOfThisDept = students.stream()
.filter(s -> (student != null
&& s.getDepartment() != null
&& s.getDepartment().getCode().equals("CS")
))
.collect(Collectors.toList());


Here I have to perform 2 check -

s.getDepartment() != null ; // 1st check


and

s.getDepartment().getCode().equals("CS") // 2nd check


Is there any way that I can store the value of
s.getDepartment()
to some variable (say
dept
) so that in second check I can write -

dept.getCode().equals("CS");

Answer

Introduce a variable after filtering null students

studentsOfThisDept = students.stream()
            .filter(s -> s != null)
            .filter(s -> {
                     Dept dept = s.getDepartment();
                     return dept != null && dept.getCode().equals("CS");
                    })
            .collect(Collectors.toList());  

filter() takes a predicate, which means the lambda block can do things like declare variables, log stuff etc. Just make sure to return a boolean at the end of the block. A predicate is a function that takes an object and returns boolean.