Lambda expression in Java?

Question

I need to switch part of my projects from C# to Java. But before which, I would like to compare two languages carefully and completely.

Regarding to lambda expression, I could write very elegant code via C#, the question is how to implement the same feature gracefully in Java? Thanks in advance!

class Program
{
    enum Gender
    {
        Male,
        Female
    }
    class Student
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }
        public Gender Gender { get; set; }
        public override string ToString()
        {
            return string.Format("Id: {0}, Name: {1}, Age: {2}, Gender: {3}", Id, Name, Age, Gender);
        }
    }

    static void Main(string[] args)
    {
        var students = new[] { 
            new Student { Id = 1, Name = "Nathanial Archibald", Age = 18, Gender = Gender.Male },
            new Student { Id = 2, Name = "Georgina Sparks", Age = 19, Gender = Gender.Female },
            new Student { Id = 3, Name = "Daniel Humphrey", Age = 20, Gender = Gender.Male },
            new Student { Id = 4, Name = "Jenny Humphrey", Age = 17, Gender = Gender.Female },
        };

        var men = students.Where(p => p.Gender == Gender.Male);
        var ageAbove18 = students.Where(p => p.Age > 18);
        var humphrey = students.Where(p => p.Name.EndsWith("Humphrey"));
        var idGT1orderbyAge = students.Where(p => p.Id > 1).OrderBy(p => p.Age);

        foreach (var s in men) Console.WriteLine(s.ToString());
        foreach (var s in ageAbove18) Console.WriteLine(s.ToString());
        foreach (var s in humphrey) Console.WriteLine(s.ToString());
        foreach (var s in idGT1orderbyAge) Console.WriteLine(s.ToString());
    }
}

Oh dear :( Not only does Java (7) not have lambda's, but the default collection library (in Java 7) lacks any sort of HoF support - nothing even comparable to LINQ. There are some non-standard libraries that can "help" with those `Where` expressions (in a Java'esque manner), but it'll take some "rewriting the crap by hand" otherwise. I think the better question is **"How is it possible [or least painful] to port this [simple] LINQ/Enumerable code to Java?"** (to avoid the trivial answers, as received). — user2246674, Jul 03 '13 at 03:50
I got it, traditional way will be used to write code like above in Java. Anyway, I'm looking forward to the day Java8 comes. — Miles Chen, Jul 03 '13 at 04:24
possible duplicate of [Lambda expressions of .NET in Java](http://stackoverflow.com/questions/4775627/lambda-expressions-of-net-in-java) — nawfal, Jul 05 '14 at 07:42
Read this article: https://smugjava.blogspot.in/2017/11/lamda-expression-in-java-8.html it wonderfully explains you lambda expression with the example of Behavioural Parameterization concept. — Jameer Mulani, Nov 11 '17 at 06:34

score 3 · Accepted Answer · 2013-07-03T04:17:07.583

3

Java in version 8 might support lambda.;)

You can use this Site or this. See this example:

final Array<Integer> a = array(1, 2, 3);  
final Array<Integer> b = a.map({int i => i + 42});  
arrayShow(intShow).println(b); // {43,44,45}

edited Jul 03 '13 at 04:17

answered Jul 03 '13 at 03:47

2

Java 8 .. might .. yeah, have fun with that :D (Java is dead to me; I wouldn't consider using it again .. well, not without a significant pay increase.) – user2246674 Jul 03 '13 at 04:16
1

Thanks everybody. Since Java doesn't support lambda currently, I will avoid using this feature and create workaround when needed. – Miles Chen Jul 03 '13 at 04:22
1

@pleasedeleteme Java 8 ... does! :-) – Stuart Marks Apr 26 '14 at 01:10

score 3 · Answer 2 · answered Jul 03 '13 at 03:49

Currently java doesn't support Lambda operation, but this will going to be introduced in Java 8. For further reference site

But as you want to switch to Java this is a good option but as long as lambda operation is not supported you can create your methods to do the same task and after java 8 release shift to the lambha operation

here is an example of lambha operation in java 8

score 1 · Answer 3 · answered Aug 09 '14 at 05:53

Java 8 supports Lambda expression. Here is how you can use lambda expression in java to sort a list of Students

private static void sort(List<Student> students) {
Comparator<Student> rollNumberComparator = (student1, student2) -> 
    student1.getRollNumber().compareTo(student2.getRollNumber());

Collections.sort(students,rollNumberComparator);

}

You can refer : http://www.groupkt.com/post/088a8dea/lambda-expressions---java-8-feature.htm

score 0 · Answer 4 · answered Jul 03 '13 at 03:46

0

Lambda expressions aren't part of the current version of Java (1.7) it is a feature for Java 8, which wont be released at least until next year

answered Jul 03 '13 at 03:46

morgano

17,210
10
45
56

score -1 · Answer 5 · answered Jul 19 '22 at 11:34

-1

Lambda expression for functional interface

answered Jul 19 '22 at 11:34

Ajay

176
6

Lambda expression in Java?

5 Answers5

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