Unary Operator

This lesson explains the Unary operator, which is a subtype of the Function interface.

We'll cover the following

UnaryOperator<T>

The UnaryOperator<T> interface represents a function that takes one argument of type T and returns a value of the same type. This is similar to the Function interface, which is a parent to the UnaryOperator interface.

The UnaryOperator does not define any new abstract methods. Since it extends the Function interface from the same package, it inherits the following method from the Function interface :

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T apply(T t)

Below are the functional interfaces, which can be categorized as unary operators
UnaryOperator<T> Represents an operation on a single operand that produces a result of the same type as its operand (reference type) T apply (T t)
DoubleUnaryOperator Accepts single double-value operand and produces a double-value result double applyAsDouble(double operand)
IntUnaryOperator Accepts a single int-value operand and produces an int-value result int applyAsInt(int operand)
LongUnaryOperator Accepts a single long-value operand and produces a long-value result long applyAsLong(long operand)

In the below example, we will create a lambda of unary operator type. It will take a Person object as input, fill data in the object, and return the same object as the output.

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import java.util.function.UnaryOperator;



public class UnaryOperatorTest {





    public static void main(String args[]) {

        Person person = new Person();

        UnaryOperator<Person> operator = (p) -> {

            p.name = "John";

            p.age = 34;

            return p;

        };



        operator.apply(person);

        System.out.println("Person Name: " + person.getName() + " Person Age: " + person.getAge());

    }

}



class Person {

    String name;

    int age;



    Person() {

    }



    Person(String name, int age) {

        this.name = name;

        this.age = age;

    }



    public void setName(String name) {

        this.name = name;

    }



    public void setAge(int age) {

        this.age = age;

    }



    public String getName() {

        return name;

    }



    public int getAge() {

        return age;

    }

}

IntUnaryOperator

This is the primitive flavor of the UnaryOperator. It takes an int as an argument and returns int as a result. We should always prefer using the primitive flavors of functional interfaces as boxing and unboxing are not good for performance.

In the below example, we will create a lambda of IntUnaryOperator type. It takes a number as input and returns its square.

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import java.util.function.IntUnaryOperator;



public class UnaryOperatorTest {





    public static void main(String args[]) {

        IntUnaryOperator operator = num -> num * num;



        System.out.println(operator.applyAsInt(25));

    }

}

In the next lesson, we will discuss the Binary operator.

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