I'll give you advice, try to create your own Pair class implementation, it's enough easy:

public class Pair<K, V> {

    private final K first;

    private final V second;

    public Pair(final K first, final V second) {
        this.first = first;
        this.second = second;
    }

    public static <K, V> Pair<K, V> of(K first, V second) {
        return new Pair<>(first, second);
    }

    public K getFirst() {
        return first;
    }

    public V getSecond() {
        return second;
    }
}

In your implementation, you can declare any constructors, static initialize methods, or deserialize's rules. It'll more comfortable than JavaFX Pair.

tl;dr

record Pair ( String string , State state ) {}

Records

The Answer by Bykov is good if you want a general mutable pair class. Alternatively, you can whip up a specific immutable pairing quite easily in Java 16+ by using the records feature.

A record is a brief way to write a class whose main purpose is to communicate data transparently and immutably. You simply declare the type and name of each member field. The compiler implicitly creates the constructor, getters, equals & hashCode, and toString.

Here is our entire class definition in six words:

record Pair ( String string , State state ) {}

You would of course use more descriptive class and field names.

Instantiate like a conventional class.

Pair p = new Pair( "whatever" , tennessee ) ;

You can declare a record locally, as well as nested or separately.

That record above is equivalent to the conventional code seen below. Modern IDEs such IntelliJ can convert a record to a conventional class, creating this source code.

package work.basil.example;

import java.util.Objects;

public final class Pair {
    private final String string;
    private final State state;

    public Pair ( String string , State state ) {
        this.string = string;
        this.state = state;
    }

    public String string () { return string; }

    public State state () { return state; }

    @Override
    public boolean equals ( Object obj ) {
        if ( obj == this ) return true;
        if ( obj == null || obj.getClass () != this.getClass () ) return false;
        var that = ( Pair ) obj;
        return Objects.equals ( this.string , that.string ) &&
                Objects.equals ( this.state , that.state );
    }

    @Override
    public int hashCode () {
        return Objects.hash ( string , state );
    }

    @Override
    public String toString () {
        return "Pair[" +
                "string=" + string + ", " +
                "state=" + state + ']';
    }

}

1. For using tuples, there's a great lib JOOL.
2. If you want to use a custom object as hash map keys, do not forger to correctly define equals() and hashCode() for this class.

UPDATE: After some suggestions here I tried to implement pair with hashmap, can you spot anything wrong with this code ?
I included this code inside a class "my_struct"

 public class tuple<Character, my_struct> extends HashMap<Character, my_struct> {

      public tuple() {
        super();
      }

      public Character getMove(HashMap<Character, my_struct> c) {
              Set<Character> w = c.keySet();
              Character move;
              for(Character i : w) {
                  move = i;
              }
              return move;
     }

      public my_struct getPrev(HashMap<Character, my_struct> c) {
          Collection<my_struct> w = c.values();
          my_struct prev;
          for(my_struct i : w) {
              prev = i;
          }
          return prev;
      }
      
  }

Then I am trying to use both get() method from HashMap class and my new methods but it won't work:

HashMap<Character, my_struct> i = new tuple();