Iterating String Array by a specific value

Question

I'm iterating over an ArrayList with String arrays inside.

["A","1"]
["A","2"]
["A","3"]
["B","1"]
["B","2"]
["B","3"]

How can I select only the ones with an "A" on the first position? Without iterating, and saving on a new array...

for (String[] key : keys){  
}

Using a for each for example, what I want is, for the first iteration -> only work with the String Arrays with "A", second iteration -> only work with the String Arrays with "B".

Guava has tools for doing things like this, but really, it seems like you want a multimap. — David Ehrmann, Jul 13 '15 at 21:22

score 2 · Accepted Answer · answered Jul 13 '15 at 21:29

Try this:

    String[][] keys = {
        {"A","1"},
        {"A","2"},
        {"A","3"},
        {"B","1"},
        {"B","2"},
        {"B","3"},
    };
    String[][] result = Stream.of(keys)
        .filter(x -> x[0].equals("A"))
        .toArray(String[][]::new);
    System.out.println(Arrays.deepToString(result));

score 0 · Answer 2 · answered Jul 13 '15 at 21:30

0

Are you looking for a solution with Java 8?

List<String[]> result = keys.stream()
                            .filter(t -> "A".equals(t[0]))
                            .collect(Collectors.toList());

answered Jul 13 '15 at 21:30

Paul Vargas

41,222
15
102
148

Can i use Java 8 in JSP? – Rayden Jul 13 '15 at 21:31
*Yup*. It depends on the application server. Are you using Tomcat 8 or Wildfly with JDK 8? What app server are you using? – Paul Vargas Jul 13 '15 at 21:41

jambriz · Answer 3 · 2015-07-13T21:48:40.123

-1

you can´t without going through each one (either iterating or in parallel). But you probably want a Map. Check this : http://docs.oracle.com/javase/7/docs/api/java/util/Map.html

edited Jul 13 '15 at 21:48

answered Jul 13 '15 at 21:22

jambriz

1,273
1
10
25

Iterating String Array by a specific value

3 Answers3