Forem: Abdallah Mahmoud

Summing Java Streams Api

Abdallah Mahmoud — Tue, 08 Feb 2022 12:13:45 +0000

Pipelines and streams are introduced in Java SE 8 and it enriches the Java collections API. Java Stream API package is to support functional style operations such as map-reduce transformations on collections. To get full documentation click this. Understanding the way stream api works Lambda expressions in java is prerequisite.

Stream

Stream is a sequence of elements supporting sequential and parallel aggregate operations.

Operations – Intermediate and terminal are two types of operations in a stream. Intermediate operation returns a new stream and terminal operation consumes a stream.

Example Stream

System.out.println("Stream Api");
List<String> names = Arrays.asList("Abdallah", "Mahmoud", "Ahmed");
        names.stream().filter(name -> name.length() > 5)
                .forEach(System.out::println);

Output:

Stream Api
Ahmed

Java Streams Operations
Java stream operation are of two types intermediate and terminal:

Intermediate Operations : returns a new stream

map()
filter()
sorted()
distinct()
limit()

Terminal Operations:consumes the stream pipeline

sum()
count()
average()
collect()
reduce()

To read more about operations in stream api click here or java streams api here.

reduce():

It applies a binary operator (accumulator) to each element in the stream, where the first operand is the return value of the previous application, and the second one is the current stream element.

Primitive Examples

 public  Integer getSumByUsingReduce(List<Integer> integers) {
        return integers.stream().reduce(0, (a, b) -> a + b);
    }

Using Java Accumulator

 public  Integer getSumByUsingJavaAccumulator(
List<Integer> integers) {
        return integers.stream().reduce(0, Integer::sum);
    }

SumUtils class

public class SumUtils {
    public static int add(int a, int b){
        return a+b;
    }
}

Using Customized Accumulator

public  Integer getSumByUsingCustomizedAccumulator(
          List<Integer> integers) {
        return integers
                    .stream()
                    .reduce(0, SumUtils::add);
    }

collect():

   public Integer getSumByUsingCustomizedAccumulator(
            List<Integer> integers) {
        return integers
                .stream()
                .reduce(0, SumUtils::add);
    }

sum():

    public Integer getSumByUsingSum(
            List<Integer> integers) {
        return integers
                .stream()
                .mapToInt(Integer::intValue)
                .sum();
    }

MapValues:

  public Integer getSumByUsingMapValues(
            Map<Integer, Integer> map) {
        return map
                .values()
                .stream()
                .mapToInt(Integer::valueOf).sum();
    }

Extracting:

  public Integer getSumByExtractingIntegersFromString(
            String str) {

        return Arrays.stream(str.split(" "))
                .filter((s) -> s.matches("\\d+"))
                .mapToInt(Integer::valueOf)
                .sum();
    }

StreamSumByUsingPrimitive Class

package com.riigsoft.streamapi.sum;

import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class StreamSumByUsingPrimitive {

    public Integer getSumByUsingReduce(
            List<Integer> integers) {
        return integers
                .stream()
                .reduce(0, (a, b) -> a + b);
    }

    public Integer getSumByUsingCollect(
            List<Integer> integers) {
        return integers
                .stream()
                .collect(Collectors
                        .summingInt(Integer::intValue));
    }

    public Integer getSumByUsingJavaAccumulator(
            List<Integer> integers) {
        return integers.stream().reduce(0, Integer::sum);
    }

    public Integer getSumByUsingCustomizedAccumulator(
            List<Integer> integers) {
        return integers
                .stream()
                .reduce(0, SumUtils::add);
    }

    public Integer getSumByUsingSum(
            List<Integer> integers) {
        return integers
                .stream()
                .mapToInt(Integer::intValue)
                .sum();
    }

    public Integer getSumByUsingMapValues(
            Map<Integer, Integer> map) {
        return map
                .values()
                .stream()
                .mapToInt(Integer::valueOf).sum();
    }

    public Integer getSumByExtractingIntegersFromString(
            String str) {

        return Arrays.stream(str.split(" "))
                .filter((s) -> s.matches("\\d+"))
                .mapToInt(Integer::valueOf)
                .sum();
    }
}

Object Examples

Product Class

package com.riigsoft.streamapi.sum;

public class Product {
    private int id;
    private int price;

    public Product(int id, int price) {
        this.id = id;
        this.price = price;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getPrice() {
        return price;
    }

    public void setPrice(int price) {
        this.price = price;
    }
}

Calculating sum of product prices:
reduce():

 public  Integer getSumByUsingReduce(List<Product> products) {
        return products.stream()
                .map(product -> product.getPrice())
                .reduce(0, (a, b) -> a + b);
    }

Reduce with Reference

  public  Integer getSumByUsingReduceWithMethodReference(
            List<Product> products) {
        return products.stream()
                .map(Product::getPrice)
                .reduce(0, (a, b) -> a + b);
    }

collect()

 public  Integer getSumByUsingCollect(List<Product> products) {
        return products.stream()
                .map(product -> product.getPrice())
                .collect(Collectors.summingInt(Integer::intValue));

Java Accumulator

  public  Integer getSumByUsingJavaAccumulator(
            List<Product> products) {
        return products.stream()
                .map(product -> product.getPrice())
                .reduce(0, Integer::sum);
    }

Customized Accumulator

  public  Integer getSumByUsingCustomizedAccumulator(
            List<Product> products) {
        return products.stream()
                .map(product -> product.getPrice())
                .reduce(0, SumUtils::add);
    }

sum()

 public  Integer getSumByUsingSum(List<Product> products) {
        return products.stream()
                .map(product -> product.getPrice())
                .mapToInt(Integer::intValue).sum();
    }

StreamSumByUsingObject Class

package com.riigsoft.streamapi.sum;

import java.util.List;
import java.util.stream.Collectors;

public class StreamSumByUsingObject {
    public  Integer getSumByUsingReduce(
            List<Product> products) {
        return products.stream()
                .map(product -> product.getPrice())
                .reduce(0, (a, b) -> a + b);
    }
    public  Integer getSumByUsingReduceWithMethodReference(
            List<Product> products) {
        return products.stream()
                .map(Product::getPrice)
                .reduce(0, (a, b) -> a + b);
    }

    public  Integer getSumByUsingCollect(
            List<Product> products) {
        return products.stream()
                .map(product -> product.getPrice())
                .collect(Collectors
                        .summingInt(Integer::intValue));
    }

    public  Integer getSumByUsingJavaAccumulator(
            List<Product> products) {
        return products.stream()
                .map(product -> product.getPrice())
                .reduce(0, Integer::sum);
    }

    public  Integer getSumByUsingCustomizedAccumulator(
            List<Product> products) {
        return products.stream()
                .map(product -> product.getPrice())
                .reduce(0, SumUtils::add);
    }


    public  Integer getSumByUsingSum(List<Product> products) {
        return products.stream()
                .map(product -> product.getPrice())
                .mapToInt(Integer::intValue).sum();
    }

}

Finally, thank you for reading this, and you can clone complete source code in my git repository here.

Springboot-GooglereCAPTCHA

Abdallah Mahmoud — Thu, 24 Jun 2021 12:00:36 +0000

GooglereCAPTCHA
I hope you doing well. Today I’ll talk about Google reCAPTCHA v2 which provided by Google API. I am using Springboot for my coding backend and Thymeleaf as my View Resolver.

Let me start.

Step#1:

Go to google and google recaptcha admin console
Login with your Gmail account
Create captcha v2 by giving name, type, owner and domain.
Then you will get two keys :

Client side key secret
Server side key secret

Step#2:

Go to https://start.spring.io/
Open your favorite IDE , I am using Intellij Idea 2021.1.2 [Community Edition]
Choose your project name,groupId and artifact.
Use java 8 and higher as your version
Select following dependencies

Spring Web
Spring Data Jpa
Thymeleaf
H2 Database for persistence
Lombok for POJO classes.

I create my project structure, I always tell my friend to structure there projects, don’t miss up everything one package.

CUSTOMER as my model class : Customer, CaptchaResponse
Repository :CustomerRepository
Services :ICustomerService, CustomerServiceImpl
Controller :CustomerController
Configuration class for reCAPTCHA :AppConfig

I can’t explain each and every line of code for this simple article but I am sharing my github link where you can clone and analysis in your own way.

GooglereCAPTCHA

Thank you All.

SpringBootCRUD with SRM Proejct

Abdallah Mahmoud — Sat, 15 May 2021 17:49:33 +0000

https://bit.ly/3okst4f

ConcurrentModificationException in Java

Abdallah Mahmoud — Sat, 20 Feb 2021 08:03:47 +0000

[https://bit.ly/3qz5mDs)

Stack and BubbleSort in Java

Abdallah Mahmoud — Fri, 29 Jan 2021 12:38:21 +0000

Please visit my git to get complete source code with clean and clear examples.
https://bit.ly/3owxTYx

Java 8 Streams.

Abdallah Mahmoud — Fri, 04 Dec 2020 10:25:03 +0000

I prepared every thing you need know about Java 8 Streams . Examples; I prepared with source code in Github. You can click link below to get more.

https://bit.ly/36Gmcsy

Simple Captch in Spring Boot

Abdallah Mahmoud — Sun, 25 Oct 2020 18:30:32 +0000

SimpleCaptcha is a simple Java library which can be used to develop random "captcha" generation for verification and validation purposes. Captcha is combination of background , text and line(noise) like below:

I used Spring boot to develop; this application is complete CRUD in which I did all necessary operation of user. User can register with verification and edit with verification and deleted also. Application allows to view all registered users also. Here is my git, you can download complete code.

https://www.linkedin.com/posts/abdallah-mahmoud-864314102_user-registration-captcha-activity-6726196313769291776-PW2K

Simple Captcha in Java

Abdallah Mahmoud — Tue, 20 Oct 2020 16:05:43 +0000

SimpleCaptcha is a simple Java library which can be used to develop random "captcha" generation for verification and validation purposes. Captcha is combination of background , text and line(noise) like below:

I used to this application simple core java coding thru [MAVEN]. This is standalone application, but in my next post I will share SimpleCaptcha by using Spring Boot . To read more about SimpleCaptcha java library go through this http://simplecaptcha.sourceforge.net/

In my git [https://github.com/abdamah/simpleCaptchaApp] you can download and trace out my code, it simple and clean code. Here you will get complete code including jars/dependencies needed to develop the application. And also it is my pleasure to your feedback