Implement Triplet class (or a 3-Tuple) in Java

This post will discuss how to implement our own Triplet class in Java.

A Triplet is a container to store a triplet of three objects. Since JDK doesn’t implement the Triplet class, some programmers often miss this class in Java. This post will discuss how to implement our own Triplet class in Java, which can be easily customized to suit our style.

Writing a Triplet class is actually very simple in Java. Following is a simple implementation of the custom Triplet class in Java, which has the following fields and methods:

Three public fields – first, second and third.
A private constructor.
Overridden hashCode() and equals() methods to ensure the desired behavior in hash-based collections.
Overridden toString() method to print the Triplet instance.
Finally, a static factory method of() for creating a typed and immutable Triplet instance which internally calls the private constructor.

The following program demonstrates it:

import java.util.ArrayList;

import java.util.HashSet;

import java.util.List;

import java.util.Set;

// Triplet class

class Triplet<U, V, T>

{

public final U first; // the first field of a triplet

public final V second; // the second field of a triplet

public final T third; // the third field of a triplet

// Constructs a new triplet with the given values

private Triplet(U first, V second, T third)

{

this.first = first;

this.second = second;

this.third = third;

}

@Override

public boolean equals(Object o)

{

/* Checks specified object is "equal to" the current object or not */

if (this == o) {

return true;

}

if (o == null || getClass() != o.getClass()) {

return false;

}

Triplet triplet = (Triplet) o;

// call `equals()` method of the underlying objects

if (!first.equals(triplet.first) ||

!second.equals(triplet.second) ||

!third.equals(triplet.third)) {

return false;

}

return true;

}

@Override

public int hashCode()

{

/* Computes hash code for an object by using hash codes of

the underlying objects */

int result = first.hashCode();

result = 31 * result + second.hashCode();

result = 31 * result + third.hashCode();

return result;

}

@Override

public String toString() {

return "(" + first + ", " + second + ", " + third + ")";

}

// Factory method for creating a typed immutable instance of triplet

public static <U, V, T> Triplet <U, V, T> of(U a, V b, T c) {

return new Triplet <>(a, b, c);

}

// Program to implement Triplet class in Java

class Main

{

public static void main(String[] args)

{

Triplet<String, Integer, Character> p1 = Triplet.of("David", 26, 'M');

Triplet<String, Integer, Character> p2 = Triplet.of("Lisa", 20, 'F');

Triplet<String, Integer, Character> p3 = Triplet.of("David", 26, 'M');

List<Triplet<String, Integer, Character>> pairs = new ArrayList<>();

pairs.add(p1);

pairs.add(p2);

pairs.add(p3);

System.out.println(pairs);

Set<Triplet<String, Integer, Character>>

distinctTriplets = new HashSet<>(pairs);

System.out.println(distinctTriplets);

}

Download Run Code

Output:

[(David, 26, M), (Lisa, 20, F), (David, 26, M)]
[(Lisa, 20, F), (David, 26, M)]

That’s all about Triplet class implementation in Java.

Implement Triplet class (or a 3-Tuple) in Java

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