Code refactoring using lambda - Java 8

Question

I was just looking into the basics of functional programming. I want to convert the below code using lambda in Java. I am using java 8. any help will be appreciated.

Thanks.

        String reinBranches = (String) application.getAttribute("xx_xx_xx");

    if(reinBranches != null && reinBranches.length() > 0)
    {
        String reinBranchArray[] = reinBranches.split(",");
        for(int i = 0; i < reinBranchArray.length; i++)
        {
            if(reinBranchArray[i].equals((String) session.getAttribute("xyz_xyz_xyz"))) {
                return true;
            }
        }
    }
    return false;

The first rule to use a lambda is: is your target interface a functional interface? — Aniket Sahrawat
– Aniket Sahrawat, Commented Mar 20, 2018 at 12:02
You mean you want to convert the implementation to one with a stream? — daniu
– daniu, Commented Mar 20, 2018 at 12:03
@AniketSahrawat : The point is i am just a newbie on functional programming. I am in a phase of trying to convert my code. I just wanted to know if i can convert this small piece into lamda or not. — Abid Ali
– Abid Ali, Commented Mar 20, 2018 at 12:05

Elliott Frisch · Accepted Answer · 2018-03-20 12:19:26Z

4

First I would get the attribute you want to match against and save it (before the lambda). Then stream the String[] from your split and return true if anyMatch your criteria. Finally, use a logical and to prevent NPE on the return. Like,

String reinBranches = (String) application.getAttribute("xx_xx_xx");
String xyz3 = (String) session.getAttribute("xyz_xyz_xyz");
return reinBranches != null && Arrays.stream(reinBranches.split(",")).anyMatch(xyz3::equals);

or as suggested in the comments using Pattern.splitAsStream which can short-circuit if a match is found without building the array from splitting

return reinBranches != null && Pattern.compile(",").splitAsStream(reinBranches).anyMatch(xyz3::equals);

edited Mar 20, 2018 at 12:19

answered Mar 20, 2018 at 12:07

Elliott Frisch

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4 Comments

Hadi Over a year ago

Pattern.compile(",").splitAsStream(reinBranches).anyMatch(s -> s.equals(session.getAttribute("xyz_xyz_xyz")));

Holger Over a year ago

There’s never a need for a boolean literal in a compound expression. In this specific case, the simplified expression is reinBranches != null && Arrays.stream(reinBranches.split(",")).anyMatch(attr::equals). Another alternative worth considering is to get rid of the split operation: reinBranches != null && reinBranches.matches( "(.*,)?"+Pattern.quote(xyz3)+"(,.*)?");

Elliott Frisch Over a year ago

@Holger Very nice. I clearly need more coffee. Keurig on!

Holger Over a year ago

Pattern.splitAsStream has the advantage of not generating an array of all substrings in advance. Since anyMatch is short-circuiting, this can truly reduce the amount of work compared to String.split+Arrays.stream. On the other hand, String.split has an optimized code path for single character separators which likely wins for small to medium sized strings…

2 revs · Accepted Answer · 2018-03-20 12:37:55Z

0

Magic

BooleanSupplier r = () -> {
    String reinBranches = (String) application.getAttribute("xx_xx_xx");

    if(reinBranches != null && reinBranches.length() > 0)
    {
        String reinBranchArray[] = reinBranches.split(",");
        for(int i = 0; i < reinBranchArray.length; i++)
        {
            if(reinBranchArray[i].equals((String) session.getAttribute("xyz_xyz_xyz"))) {
                return true;
            }
        }
    }
    return false;
}

edited Mar 20, 2018 at 12:37

community wiki

2 revs
Michael

1 Comment

Michael Over a year ago

@Holger also, it's community wiki so you could've just edited it

Vinay Prajapati · Accepted Answer · 2018-03-20 19:36:12Z

0

Just another way of doing same without any overhead of using streams:-

String reinBranches = (String) application.getAttribute("xx_xx_xx");
String xyz3 = (String) session.getAttribute("xyz_xyz_xyz");

return reinBranches != null && Pattern.compile(xyz3).matcher(reinBranches).find(0);

answered Mar 20, 2018 at 19:36

Vinay Prajapati

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