A Pair is a Tuple from JavaTuples library that deals with 2 elements. Since this Pair is a generic class, it can hold any type of value in it.
Since Pair is a Tuple, hence it also has all the characterstics of JavaTuples:
- They are Typesafe
- They are Immutable
- They are Iterable
- They are Serializable
- They are Comparable (implements Comparable<Tuple>)
- They implement equals() and hashCode()
- They also implement toString()
Class Declaration
public final class Pair<A, B> extends Tuple
implements IValue0<A>, IValue1<B>
Class hierarchy
Object
↳ org.javatuples.Tuple
↳ org.javatuples.Pair<A, B>
Creating Pair Tuple
From Constructor:
Syntax:
Pair<A, B> pair = new Pair<A, B>(value1, value2);
Example:
// Below is a Java program to create
// a Pair tuple from Constructor
import java.util.*;
import org.javatuples.Pair;
class Prutor {
public static void main(String[] args)
{
Pair<Integer, String> pair
= new Pair<Integer, String>(Integer.valueOf(1), "PrutordotAi");
System.out.println(pair);
}
}
Output:
[1, PrutordotAi]
Using with() method: The with() method is a function provided by the JavaTuples library, to instantiate the object with such values.
Syntax:
Pair<type1, type2> pair = Pair.with(value1, value2);
Example:
// Below is a Java program to create
// a Pair tuple from with() method
import java.util.*;
import org.javatuples.Pair;
class Prutor {
public static void main(String[] args)
{
Pair<Integer, String> pair
= Pair.with(Integer.valueOf(1), "PrutordotAi");
System.out.println(pair);
}
}
Output:
[1, PrutordotAi]
From other collections: The fromCollection() method is used to create a Tuple from a collection, and fromArray() method is used to create from an array. The collection/array must have the same type as of the Tuple and the number of values in the collection/array must match the Tuple class.
Syntax:
Pair<type1, type2> pair = Pair.fromCollection(collectionWith_2_value);
Pair<type1, type2> pair = Pair.fromArray(arrayWith_2_value);
Example:
// Below is a Java program to create
// a Pair tuple from Collection
import java.util.*;
import org.javatuples.Pair;
class Prutor {
public static void main(String[] args)
{
// Creating Pair from List
List<String> list = new ArrayList<String>();
list.add("PrutordotAi");
list.add("A coding Lab");
Pair<Strin, String> pair
= Pair.fromCollection(list);
// Creating Pair from Array
String[] arr = { "PrutordotAi", "A coding Lab" };
Pair<String, String> otherPair
= Pair.fromArray(arr);
System.out.println(pair);
System.out.println(otherPair);
}
}
Output:
[PrutordotAi, A coding Lab]
[PrutordotAi, A coding Lab]
Getting Value
The getValueX() method can be used to fetch the value in a Tuple at index X. The indexing in Tuples start with 0. Hence the value at index X represents the value at position X+1.
Syntax:
Pair<type1, type2> pair =
new Pair<type1, type2>(value1, value2);
type1 val1 = pair.getValue0();
Example:
// Below is a Java program to get
// a Pair value
import java.util.*;
import org.javatuples.Pair;
class Prutor {
public static void main(String[] args)
{
Pair<Integer, String> pair
= Pair.with(Integer.valueOf(1), "PrutordotAi");
System.out.println(pair.getValue0());
}
}
Output:
1
Setting Pair Value
Since the Tuples are immutable, it means that modifying a value at an index is not possible. Hence, JavaTuples offer setAtX(value) which creates a copy of the Tuple with a new value at index X, and returns that Tuple.
Syntax:
Pair<type1, type2> pair =
new Pair<type1, type2>(value1, value2);
type1 val1 = pair.getValue0();
Example:
// Below is a Java program to set
// a Pair value
import java.util.*;
import org.javatuples.Pair;
class Prutor {
public static void main(String[] args)
{
Pair<Integer, String> pair
= Pair.with(Integer.valueOf(1), "PrutordotAi");
Pair<Integer, String> otherPair
= pair.setAt1("A coding Lab");
System.out.println(otherPair);
}
}
Output:
[1, A coding Lab]
Adding a Value
Adding a value can be done with the help of addAtX() method, where X represents the index at which the value is to be added. This method returns a Tuple of element one more than the called Tuple.
Syntax:
Pair<type1, type2> pair =
new Pair<type1, type2>(value1, value2);
Triplet<type 1, type 2, type 3> pair =
pair.addAt2(value 2);
Example:
// Below is a Java program to add
// a value
import java.util.*;
import org.javatuples.Pair;
import org.javatuples.Triplet;
class Prutor {
public static void main(String[] args)
{
Pair<Integer, String> pair
= Pair.with(Integer.valueOf(1), "PrutordotAi");
Triplet<Integer, String, String> triplet
= pair.addAt2("A coding Lab");
System.out.println(triplet);
}
}
Output:
[1, PrutordotAi, A coding Lab]
Searching in Pair
An element can be searched in a tuple with the pre-defined method contains(). It returns a boolean value whether the value is present or not.
Syntax:
Pair<type1, type2> pair =
new Pair<type1, type2>(value1, value2);
boolean res = pair.contains(value2);
Example:
// Below is a Java program to search
// a value
import java.util.*;
import org.javatuples.Pair;
class Prutor {
public static void main(String[] args)
{
Pair<Integer, String> pair
= Pair.with(Integer.valueOf(1), "PrutordotAi");
boolean exist = pair.contains("PrutordotAi");
boolean exist1 = pair.contains(4);
System.out.println(exist);
System.out.println(exist1);
}
}
Output:
true
false
Iterating through Pair
Since Pair implement the Iterable<Object> interface. It means that they can be iterated in the same way as collections or arrays.
Syntax:
Pair<type1, type2> pair =
new Pair<type1, type2>(value1, value2);
for (Object item : pair) {
...
}
Example:
// Below is a Java program to iterate
// a Pair
import java.util.*;
import org.javatuples.Pair;
class Prutor {
public static void main(String[] args)
{
Pair<Integer, String> pair
= Pair.with(Integer.valueOf(1), "PrutordotAi");
for (Object item : pair)
System.out.println(item);
}
}
Output:
1
PrutordotAi