Click here to watch in Youtube :
https://www.youtube.com/watch?v=_kVLMbpop-I&list=UUhwKlOVR041tngjerWxVccw
Author.java
public class Author
{
private String name;
private String email;
private int age;
private char gender;
public Author(String name, String email, int age, char gender)
{
super();
this.name = name;
this.email = email;
this.age = age;
this.gender = gender;
}
public String getName()
{
return name;
}
public void setName(String name)
{
this.name = name;
}
public String getEmail()
{
return email;
}
public void setEmail(String email)
{
this.email = email;
}
public int getAge()
{
return age;
}
public void setAge(int age)
{
this.age = age;
}
public char getGender()
{
return gender;
}
public void setGender(char gender)
{
this.gender = gender;
}
}
Book.java
public class Book
{
private String name;
private Author author;
private double price;
public Book(String name, Author author, double price)
{
super();
this.name = name;
this.author = author;
this.price = price;
}
public String getName()
{
return name;
}
public void setName(String name)
{
this.name = name;
}
public Author getAuthor()
{
return author;
}
public void setAuthor(Author author)
{
this.author = author;
}
public double getPrice()
{
return price;
}
public void setPrice(double price)
{
this.price = price;
}
}
StreamDemo.java
import java.util.ArrayList;
import java.util.List;
/**
*
* How to get the sum of ages of all male authors younger than 50.
*
*/
public class StreamDemo
{
public static void main(String[] args)
{
List<Book> bookList = new ArrayList<Book>();
// Adding Books
bookList.add(new Book("Java Basics",
new Author("Peter", "peter@yahoo.com", 20, 'M'),1000.50));
bookList.add(new Book("Mysql Basics",
new Author("Steve", "steve@yahoo.com", 30, 'M'),2000.0));
bookList.add(new Book("Oracle Basics",
new Author("John", "john@yahoo.com", 40, 'M'),3000.0));
bookList.add(new Book("Angular Basics",
new Author("Juli", "juli@yahoo.com", 55, 'F'),3000.0));
bookList.add(new Book("Jquery Basics",
new Author("Dave", "dave@yahoo.com", 65, 'M'),1000.0));
/*
* Using the same original stream we once again map the
* elements from Books to Authors and filter just on those
* authors that are male. Next we map the elements from
* Authors to author ages which gives us a stream of ints. We
* filter ages to just those that are less than 50 and use a
* reduce operation and Integer::sum to total the ages.
*/
Integer sumOfMaleAuthorAge =
bookList.stream()//Stream<Book>
.map(Book::getAuthor) //Stream<Book> to Stream<Author>.
.filter(author -> author.getGender() == 'M') // filter the male Authors.
.map(Author::getAge)//Stream<Author> to Stream<age>.
.filter(age -> age < 50)//filter the age<50.
.reduce(0, Integer::sum);// calculate the sum of ages.
System.out.println("sumOfMaleAuthorAge = " + sumOfMaleAuthorAge);
}
}
Output
sumOfMaleAuthorAge = 90
Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/StreamDemo_Book_Auther_sum_age_App.zip?attredirects=0&d=1
Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/StreamDemo_Book_Auther_sum_age_App
Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/28b768ba4f37f4b22418a8a2d2a1f53c7d0de625/BasicJava/StreamDemo_Book_Auther_sum_age_App/?at=master
See also:
All JavaEE Viedos Playlist
All JavaEE Viedos
All JAVA EE Links
Servlets Tutorial
All Design Patterns Links
JDBC Tutorial
Java Collection Framework Tutorial
JAVA Tutorial
Kids Tutorial
