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javalistsortinglambdajava-8
Hunter Tipton
Hunter Tipton

Reputation: 333

Sorting List of Arrays by different elements using Java 8 lambdas

If I have a List<String[]> in which each String[] is as follows: {FirstName, LastName, Income, City} how would I go about using Java 8 lambdas to sort the List by a certain value such as income or first name?

Upvotes: 3

Views: 931

Answers (2)

Eugene
Eugene

Reputation: 120848

If you can rely on the order in this array, then as simple as:

List<String[]> list = Arrays.asList(new String[] { "eugene", "test", "300", "LA" }, 
                              new String[] { "hunter", "test2", "25", "CA" });

 List<String[]> sorted = list.stream()
            .sorted(Comparator.comparingLong(s -> Long.parseLong(s[2])))
            .collect(Collectors.toList());

    sorted.forEach(s -> System.out.println(Arrays.toString(s)));

But the general advice to create an Object from those fields is much better.

Upvotes: 2

Matt Goodrich
Matt Goodrich

Reputation: 5095

Here's a couple examples. Replace x in the first two examples below with the index of the field you'd like to use for sorting.

Collections.sort(personList, (p1, p2) -> p1[x].compareTo(p2[x]));

or

personList.sort((p1, p2) -> p1[x].compareTo(p2[x]);

Also, I agree with @Robin Topper's comment. If lambdas are required (and you wanted to sort by first name), you could use:

Collections.sort(personList, (p1, p2) -> p1.getFirstName().compareTo(p2.getFirstName()));

or

personList.sort((p1, p2) -> p1.getFirstName().compareTo(p2.getFirstName()));

Also consider using the comparable implementation from Robin's comment and a data-structure allowing sorting.

Upvotes: 5

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