Tuple in Java lang

Question

I would like to do something with Java like Python.

data = [
    ('1','One'),
    ('2','Two'),
    ('3','Three')
] # Please, Java, how can do that ?

### List<Integer, Double> data = new ArrayList<Integer, Double>() ???
### Or
### ArrayList<Integer, Double> data = new ArrayList<>() ????
## Or more ???

for datium in data:
    print(f"{datium[0]} - {datium[1]}")

Please help.

There aren't any integers in your Python code there. That's a list of tuples of strings. Java doesn't have tuples, so there isn't really an equivalent. You could use a List<List<String>> if you want. Or write a class. — khelwood, Commented May 1, 2021 at 9:55
BTW we can do Map.of('1', "One", '2', "Two", '3', "Three") — user85421, Commented Nov 20, 2023 at 13:40

JP Moresmau · Accepted Answer · 2021-05-01 09:56:40Z

2

There are no first-class support for Tuples in Java. You can

write a little class with the fields you want
use something like javatuples library (https://www.javatuples.org/)
use something from utility libraries like Commons-lang (https://commons.apache.org/proper/commons-lang/javadocs/api-release/org/apache/commons/lang3/tuple/MutablePair.html) (note there is also an ImmutablePair)

answered May 1, 2021 at 9:56

JP Moresmau

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Comments

Amol Thakurdware · Accepted Answer · 2021-05-01 11:05:52Z

Well not exactly the same. But this should solve your purpose.

package solutions;

import java.util.HashMap;
import java.util.Map;
import java.util.Set;


public class MapExample {

    public static void main(String[] args) {
        Map<Integer, String> m=new HashMap<Integer, String>();
        m.put(1, "One");
        m.put(2, "Two");
        m.put(3, "Three");
        
        Set<Integer> keySet = m.keySet();
        for(Integer key:keySet) {
            System.out.println(key+"  "+m.get(key));
        }
        
    }

}

Kaplan · Accepted Answer · 2021-05-01 14:22:53Z

1

use of record
since Java 16
preview in Java 14:
https://docs.oracle.com/en/java/javase/14/language/records.html

record Pair(String n, String s) {};

Pair[] data = {             /* as array */
    new Pair("1", "One"),
    new Pair("2", "Two"),
    new Pair("3", "Three")};

List<Pair> data = List.of(  /* as list */
    new Pair("1", "One"),
    new Pair("2", "Two"),
    new Pair("3", "Three"));

(You should define more meaningful variable names, depending on the use case in Pair)

edited May 1, 2021 at 14:22

answered May 1, 2021 at 14:17

Kaplan

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1 Comment

Soid Over a year ago

This is actually as close as we can get to tuples in Java. I will only add that to access the field, use the name with () e.g. p.n() or p.s() for the above example

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