java.util.function.IntPredicate implementation using Modern Java

In this blog, I am going to show how to implement IntPredicate using lambdas.

And, use them to do useful work.

I am going to create a person class. Which has three properties, age, salary and name.

And, I will use lambdas to find count of person, who are above thirty years of age or has salary more than 50,000.

class Person {
        private int salary;
        private int age;
    private String name;

    public Person(final String name, final int age, final int salary){
        if(name == null || name.trim().isEmpty()) 
            throw new IllegalArgumentException("Name can not be empty");
        this.name = name;

        if(age < 0) 
            throw new IllegalArgumentException("Age Can not be less than zero");
        this.age = age;

        if(salary < 0) 
            throw new IllegalArgumentException("Salary Can not be less than zero");
        this.salary = salary;
    }

    public String getName(){ return name; }
    public int getAge() { return age; }
    public int getSalary() { return salary; }

    public void setName(final String name){ this.name = name; }
        public void setAge(final int age){ this.age = age; }
        public void setSalary(final int salary){ this.salary = salary; }
    }

Now, I will create lambdas to implement the IntPredicate interface.

final static IntPredicate i_greaterThanThirty = (int age) -> age > 30;
final static IntPredicate ageAboveThirty      = (age) -> age > 30;

final static IntPredicate salaryAbove20K      = (int salary) -> salary > 20_000;
final static IntPredicate salaryAbove50K      = (int salary) -> salary > 50_000;

Let us create list of person objects.

final IntPredicateImpl parentObj = new IntPredicateImpl();

final Person personOne    =   parentObj.new Person("Anurag", 35, 50_000);
final Person personTwo    =   parentObj.new Person("Rajneesh", 20, 20_000);
final Person personThree  =   parentObj.new Person("Durgesh", 41, 12_000);
final Person personFour   =   parentObj.new Person("Kamlesh", 25, 70_000);

List<Person> listOfPerson = List.of(personOne, personTwo, personThree, personFour);

Then use the lamdbas to filter out the peron and get the count.

long totalPersonAboveThirty = listOfPerson
                                       .stream()
                                       .mapToInt(Person::getAge)
                       .filter(ageAboveThirty)
                       .count();

System.out.format("Total Person above thirty %d.%n", totalPersonAboveThirty);
long totalNoOfPeopleWithSalaryAbove50k = listOfPerson
                                                         .stream()
                                 .mapToInt(Person::getSalary)
                                 .filter(salaryAbove50K)
                                 .count();
System.out.format("Total Number of person with salary more than 50K %d.%n", totalNoOfPeopleWithSalaryAbove50k);

You can watch my video on youtube, where I code this example.

Full Source Code :- 

import java.util.function.IntPredicate;
import java.util.List;
//IllegalArgumentException
class IntPredicateImpl{
    class Person {
        private int salary;
        private int age;
    private String name;

    public Person(final String name, final int age, final int salary){
        if(name == null || name.trim().isEmpty()) 
            throw new IllegalArgumentException("Name can not be empty");
        this.name = name;

        if(age < 0) 
            throw new IllegalArgumentException("Age Can not be less than zero");
        this.age = age;

        if(salary < 0) 
            throw new IllegalArgumentException("Salary Can not be less than zero");
        this.salary = salary;
    }

    public String getName(){ return name; }
    public int getAge() { return age; }
    public int getSalary() { return salary; }

    public void setName(final String name){ this.name = name; }
        public void setAge(final int age){ this.age = age; }
        public void setSalary(final int salary){ this.salary = salary; }
    }

    final static IntPredicate i_greaterThanThirty = (int age) -> age > 30;
    final static IntPredicate ageAboveThirty      = (age) -> age > 30;

    final static IntPredicate salaryAbove20K      = (int salary) -> salary > 20_000;
    final static IntPredicate salaryAbove50K      = (int salary) -> salary > 50_000;

    public static void main(final String ... args){
        final IntPredicateImpl parentObj = new IntPredicateImpl();

        final Person personOne    =   parentObj.new Person("Anurag", 35, 50_000);
        final Person personTwo    =   parentObj.new Person("Rajneesh", 20, 20_000);
        final Person personThree  =   parentObj.new Person("Durgesh", 41, 12_000);
        final Person personFour   =   parentObj.new Person("Kamlesh", 25, 70_000);

        List<Person> listOfPerson = List.of(personOne, personTwo, personThree, personFour);
        
    long totalPersonAboveThirty = listOfPerson
                                       .stream()
                                       .mapToInt(Person::getAge)
                       .filter(ageAboveThirty)
                       .count();

    System.out.format("Total Person above thirty %d.%n", totalPersonAboveThirty);

    long totalNoOfPeopleWithSalaryAbove50k = listOfPerson
                                                         .stream()
                                 .mapToInt(Person::getSalary)
                                 .filter(salaryAbove50K)
                                 .count();
       System.out.format("Total Number of person with salary more than 50K %d.%n", totalNoOfPeopleWithSalaryAbove50k);
    }
}