Replace two nested for loops with java 8 API

Question

I have the following snippet and I wonder if and how it is possible to replace it with Streams/Java 8 API

for (State state : states) {
    for (City city : cities) {
        if (state.containsPoint(city.getLocation())) {
            System.out.printf("%30s is part of %-30s\n",
                    city.getName(), state.getName());
        }
    }
}

Just as a note, while it's possible to convert such loop with the Stream API, I don't think you gain in readability in this case and I would stick with this for-loop. — Alexis C.
– Alexis C., Commented May 21, 2015 at 14:49
Yeah, definitely. But I was curious how a solution could look like — tplacht
– tplacht, Commented May 21, 2015 at 15:18
@AlexisC. - Makes sense. Like this nested for loop example, are there any general guidelines on when it is better to NOT use lambdas and streams ? — Java Impatient
– Java Impatient, Commented Mar 7, 2020 at 21:13

Vartlok · Accepted Answer · 2017-12-27 11:15:12Z

43

Will be something like that:

// first loop
states.forEach(state -> { 
    // second loop for filtered elements
    cities.stream().filter(city -> state.containsPoint(city.getLocation())).forEach(city -> { 
        System.out.printf("%30s is part of %-30s\n", city.getName(), state.getName());
    });
});

edited Dec 27, 2017 at 11:15

answered May 21, 2015 at 14:24

Vartlok

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2 Comments

tplacht Over a year ago

That was fast. Thanks i will give it a try

Tagir Valeev Over a year ago

You can omit streaming the states and simply use states.forEach.

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