Here's how to implement a pair-by-unit class:

1. Using direct values 

import java.util.*;
import org.javatuples.*;

class GfG {

	public static void main(String[] args)
	{
		// Create a Unit
		Unit unit = new Unit("GeeksforGeeks");

		// print unit
		System.out.println("Unit: " + unit);

		// create Pair from Unit
		Pair<Integer, String>
			pair = new Pair<Integer, String>(
				Integer.valueOf(1), unit.getValue0());

		// Print the Pair
		System.out.println("Pair: " + pair);
	}
}

Output:

Unit: [GeeksforGeeks]
Pair: [1, GeeksforGeeks]

2. Using Unit.add() method

// Below is a Java program to demonstrate
// use of add() method with
// single value

import java.util.*;
import org.javatuples.*;

class GfG {
	public static void main(String[] args)
	{
		// Using with() method to instantiate unit object
		Unit unit = Unit.with("Geeks");

		// print unit
		System.out.println("Unit: " + unit);

		// Using add() to create Pair
		Pair<String, String> pair = unit.add("forGeeks");

		// Print the Pair
		System.out.println("Pair: " + pair);
	}
}

Output:

Unit: [Geeks]
Pair: [Geeks, forGeeks]

3. Using Unit.addAtX() method

• Program 1: 
  Adding Unit at Position 0 using addAt0()
   

// Below is a Java program to demonstrate
// use of addAt0() method with
// direct value

import java.util.*;
import org.javatuples.Unit;
import org.javatuples.Pair;

class GfG {
	public static void main(String[] args)
	{
		// Using with() method to instantiate unit object
		Unit unit = Unit.with("Geeks");

		// print unit
		System.out.println("Unit: " + unit);

		// Using addAtX() to create Pair
		Pair<String, String> pair = unit.addAt0("forGeeks");

		// Print the Pair
		System.out.println("Pair: " + pair);
	}
}

Output:

Unit: [Geeks]
Pair: [forGeeks, Geeks]

• Program 2:  Adding Unit at Position 1 using addAt1()

// Below is a Java program to demonstrate
// use of addAt1() method with
// direct value

import java.util.*;
import org.javatuples.Unit;
import org.javatuples.Pair;

class GfG {
	public static void main(String[] args)
	{
		// Using with() method to instantiate unit object
		Unit unit = Unit.with("Geeks");

		// print unit
		System.out.println("Unit: " + unit);

		// Using addAtX() to create Pair
		Pair<String, String> pair = unit.addAt1("forGeeks");

		// Print the Pair
		System.out.println("Pair: " + pair);
	}
}

Output:

Unit: [Geeks]
Pair: [Geeks, forGeeks]