A KeyValue is a Tuple from JavaTuples library that deals with only 2 elements – a key and a value. Since this KeyValue is a generic class, it can hold any type of value in it.
Since KeyValue 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 KeyValue<A, B> extends Tuple
implements IValueKey<A>, IValueValue<B>
Class hierarchy
Object
↳ org.javatuples.Tuple
↳ org.javatuples.KeyValue<A, B>
Creating KeyValue Tuple
From Constructor:
Syntax:
KeyValue<A, B> kv = new KeyValue<A, B>(value1, value2);
Example:
// Below is a Java program to create
// a KeyValue tuple from Constructor
import java.util.*;
import org.javatuples.KeyValue;
class Prutor {
public static void main(String[] args)
{
KeyValue<Integer, String> kv
= new KeyValue<Integer, String>(Integer.valueOf(1), "PrutordotAi");
System.out.println(kv);
}
}
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:
KeyValue<type1, type2> kv = KeyValue.with(value1, value2);
Example:
// Below is a Java program to create
// a KeyValue tuple from with() method
import java.util.*;
import org.javatuples.KeyValue;
class Prutor {
public static void main(String[] args)
{
KeyValue<Integer, String> kv
= KeyValue.with(Integer.valueOf(1), "PrutordotAi");
System.out.println(kv);
}
}
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:
KeyValue<type1, type2> kv = KeyValue.fromCollection(collectionWith_2_value);
KeyValue<type1, type2> kv = KeyValue.fromArray(arrayWith_2_value);
Example:
// Below is a Java program to create
// a KeyValue tuple from Collection
import java.util.*;
import org.javatuples.KeyValue;
class Prutor {
public static void main(String[] args)
{
// Creating KeyValue from List
List<String> list = new ArrayList<String>();
list.add("PrutordotAi");
list.add("A coding Lab");
KeyValue<String, String> kv
= KeyValue.fromCollection(list);
// Creating KeyValue from Array
String[] arr = { "PrutordotAi", "A coding Lab" };
KeyValue<String, String> otherKeyValue
= KeyValue.fromArray(arr);
System.out.println(kv);
System.out.println(otherKeyValue);
}
}
Output:
[PrutordotAi, A coding Lab]
[PrutordotAi, A coding Lab]
Getting Value
The getValue() and getKey() methods can be used to fetch the value and key respectively in a KeyValue Tuple.
getKey():
Syntax:
KeyValue<type1, type2> kv =
new KeyValue<type1, type2>(value1, value2);
type2 val1 = kv.getKey();
Example:
// Below is a Java program to get
// a KeyValue value
import java.util.*;
import org.javatuples.KeyValue;
class Prutor {
public static void main(String[] args)
{
KeyValue<Integer, String> kv
= KeyValue.with(Integer.valueOf(1), "PrutordotAi");
System.out.println(kv.getKey());
}
}
Output:
1
getValue():
Syntax:
KeyValue<type1, type2> kv =
new KeyValue<type1, type2>(value1, value2);
type2 val1 = kv.getValue();
Example:
// Below is a Java program to get
// a KeyValue value
import java.util.*;
import org.javatuples.KeyValue;
class Prutor {
public static void main(String[] args)
{
KeyValue<Integer, String> kv
= KeyValue.with(Integer.valueOf(1), "PrutordotAi");
System.out.println(kv.getValue());
}
}
Output:
PrutordotAi
Setting KeyValue Value
Since the Tuples are immutable, it means that modifying a value at an index is not possible. Hence, JavaTuples offer setKey(value) and setValue(value) which creates a copy of the KeyValue with a new value according to method used, and returns a new KeyValue object.
setKey():
Syntax:
KeyValue<type1, type2> kv =
new KeyValue<type1, type2>(value1, value2);
KeyValue<type1, type2> kvNew = kv.setKey(valueNew);
Example:
// Below is a Java program to set
// a KeyValue Key
import java.util.*;
import org.javatuples.KeyValue;
class Prutor {
public static void main(String[] args)
{
KeyValue<Integer, String> kv
= KeyValue.with(Integer.valueOf(1), "PrutordotAi");
KeyValue<Integer, String> otherKeyValue
= kv.setKey(10);
System.out.println(otherKeyValue);
}
}
Output:
[10, PrutordotAi]
setValue():
Syntax:
KeyValue<type1, type2> kv =
new KeyValue<type1, type2>(value1, value2);
KeyValue<type1, type2> kvNew = kv.setValue(valueNew);
Example:
// Below is a Java program to set
// a KeyValue Value
import java.util.*;
import org.javatuples.KeyValue;
class Prutor {
public static void main(String[] args)
{
KeyValue<Integer, String> kv
= KeyValue.with(Integer.valueOf(1), "PrutordotAi");
KeyValue<Integer, String> otherKeyValue
= kv.setValue("A computer science portal");
System.out.println(otherKeyValue);
}
}
Output:
[1, A computer science portal]
Searching in KeyValue
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:
KeyValue<type1, type2> kv =
new KeyValue<type1, type2>(value1, value2);
boolean res = kv.contains(value2);
Example:
// Below is a Java program to search
// a value
import java.util.*;
import org.javatuples.KeyValue;
class Prutor {
public static void main(String[] args)
{
KeyValue<Integer, String> kv
= KeyValue.with(Integer.valueOf(1), "PrutordotAi");
// Using contains for True result
boolean exist = kv.contains("PrutordotAi");
// Using contains for False result
boolean exist1 = kv.contains(4);
System.out.println(exist);
System.out.println(exist1);
}
}
Output:
true
false
Iterating through KeyValue
Since KeyValue implement the Iterable<Object> interface. It means that they can be iterated in the same way as collections or arrays.
Syntax:
KeyValue<type1, type2> kv =
new KeyValue<type1, type2>(value1, value2);
for (Object item : kv) {
...
}
Example:
// Below is a Java program to iterate
// a KeyValue
import java.util.*;
import org.javatuples.KeyValue;
class Prutor {
public static void main(String[] args)
{
KeyValue<Integer, String> kv
= KeyValue.with(Integer.valueOf(1), "PrutordotAi");
for (Object item : kv)
System.out.println(item);
}
}
Output:
1
PrutordotAi