Lambda expression if-else statement

Question

Hello I Just started learning Lambda expressions, how do I write this with Lambda expressions?

  public static void greaterThanFive(String str){
    if(str.length() > 5){
        System.out.println("String length is larger than 5 ");
    }else{
        System.err.println("String length less than 5");
    }

if it was just an, if statement I could just do this:

Predicate<String> greaterThanFive = (s)-> s.length() > 5;

But I can't really figure out when it's an if-else statement.

I just want the example I just posted Lamda Expresion. Can't really see what this has to do with the example I have posted. — Peter Barnes, May 10 '16 at 19:41
Could you post a real example of what you want then? Is it `if (greaterThanFive.test(str)) {... } else {...}`? — Tunaki, May 10 '16 at 19:41
Tunaki, I can't figure out how to do an Lamda Expression when its if-else statement, so I just want the example in Lamda Expression. YES — Peter Barnes, May 10 '16 at 19:47

score 0 · Answer 1 · answered May 10 '16 at 19:54

0

Comparator<String> c = (String first, String second) -> {
if (first.length() < second.length()) return -1;
else if (first.length() > second.length()) return 1;
else return 0;
};

I believe this answers your question. For more info, read Java8 for really impatient. Its a really good book.

answered May 10 '16 at 19:54

Prudvinath

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Hmm is it not possible using filter instead of the if statement? – Peter Barnes May 10 '16 at 20:00
I believe filter can only be called on a stream and any intermediate operation on a stream results in another stream. So, we may not achieve the desired outcome you are expecting (This is to my knowledge, I'm also learning java). – Prudvinath May 10 '16 at 20:29

The SE I loved is dead · Answer 2 · 2016-05-10T20:25:43.417

0

Using blocks, you can create lambda expressions that have multiple statements or big statements (like an if-else). Example:

new Thread( () -> { // Btw, you can use java.lang.Runnable with a lambda
    System.out.println("A wild NEW THREAD appeared!"); // :)
    try {
        Thread.sleep(5000);
    } catch (InterruptedException e) {}
    System.out.println("Enemy NEW THREAD ran away!");
});

This means all you have to do is to enclose that if-else in the block of a lambda:

Consumer<String> greaterThanFive = (s) -> {
    // ...
};

Note that there's a semicolon after the block.

edited May 10 '16 at 20:25

answered May 10 '16 at 20:13

The SE I loved is dead

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Are there more convenient Funktional interface than Predicate for this kind of stuff like comparator? – Peter Barnes May 10 '16 at 20:22
It depends. Here, you should use a `Consumer` because the method you're trying to convert into a lambda expression returns `void` (I didn't look at the return type before the edit :/). `Predicate` is for converting methods that return a `boolean`. – The SE I loved is dead May 10 '16 at 20:29

Lambda expression if-else statement

2 Answers2