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Commit 486f1dc

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[yuvrajs] Method References and Operations on Custom Class
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‎README.md

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@@ -19,28 +19,53 @@ Functional programming is a paradigm that allows programming using expressions i
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2020

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## Implementations using Functional Programming
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### Using Streams, Filters and Lambdas:
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* [Print each element from list in its own line](/src/main/java/com/ysingh/functional/FP01PrintListElement.java)
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* [Print courses, courses having name with Spring, courses having name greater than 3 characters](src/main/java/com/ysingh/functional/FP02CourseExcerise.java)
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### Using Map:
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* [Print Square of each number in the list](src/main/java/com/ysingh/functional/FP03PrintSquareOfEachListElement.java)
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### Using Reduce:
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* [Print sum of all elements in the list](src/main/java/com/ysingh/functional/FP04AddNumbersInList.java)
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* [Print max and min number from all elements in the list](src/main/java/com/ysingh/functional/FP05MaximumAndMinimumNumberInList.java)
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* [Square every number in a list and find the sum of squares](src/main/java/com/ysingh/functional/FP06Excersise.java)
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* [Cube every number in a list and find the sum of cubes](src/main/java/com/ysingh/functional/FP06Excersise.java)
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* [Find sum of odd numbers in a list](src/main/java/com/ysingh/functional/FP06Excersise.java)
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### Using Distinct and Sorted:
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* [Print distinct numbers in the list](src/main/java/com/ysingh/functional/FP07DistinctAndSorted.java)
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* [Sort list of numbers and print it](src/main/java/com/ysingh/functional/FP07DistinctAndSorted.java)
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* [Sort list of strings and print it](src/main/java/com/ysingh/functional/FP07DistinctAndSorted.java)
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### Using Collect:
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* [Square each element of list and collect it as new list](src/main/java/com/ysingh/functional/FP08Collect.java)
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* [Find all even element of list and collect it as new list](src/main/java/com/ysingh/functional/FP08Collect.java)
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* [Find length of each course element of list and collect it as new list](src/main/java/com/ysingh/functional/FP08Collect.java)
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### Using allMatch, noneMatch, anyMatch:
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* [Example](src/main/java/com/ysingh/functional/FP12CustomClass.java)
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### Using Comparator:
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* [Example](src/main/java/com/ysingh/functional/FP12CustomClass.java)
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### Using skip, limit:
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* [Example](src/main/java/com/ysingh/functional/FP12CustomClass.java)
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### Using max, min, findFirst, findAny:
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* [Example](src/main/java/com/ysingh/functional/FP12CustomClass.java)
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### Using sum, average, count:
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* [Example](src/main/java/com/ysingh/functional/FP12CustomClass.java)
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### Using groupingBy:
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* [Example](src/main/java/com/ysingh/functional/FP12CustomClass.java)
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### Terminal or Intermediate operations:
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* Function or method which returns another stream of element called as Intermediate functions or methods or operations.
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* Function or method which does not return another stream of element called as Terminal functions or methods or operations.
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### Functional Interfaces:
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A functional interface has exactly one abstract method.
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* **Predicate\<T\>:** Represents a predicate (boolean-valued function) of one argument.
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* [Example](src/main/java/com/ysingh/functional/FP09FunctionalInterface.java)
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* **IntUnaryOperator:** Represents an operation on a single int-valued operand that produces an int-valued result.
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* [Example](src/main/java/com/ysingh/functional/FP09FunctionalInterface.java)
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### Behavior Parameterization:
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Passing the behaviour as parameter or argument to a method is called as Behavior Parameterization.
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* [Example](src/main/java/com/ysingh/functional/FP10BehaviourParameterization.java)
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* [Example](src/main/java/com/ysingh/functional/FP10BehaviourParameterization.java)
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### Method Reference:
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Method reference is used to refer method of functional interface. The Method reference can only be used to replace a single method of lambda expression.
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* [Example](src/main/java/com/ysingh/functional/FP11MethodReferences.java)
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package com.ysingh.functional;
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import java.util.Arrays;
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import java.util.List;
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import java.util.function.Supplier;
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public class FP11MethodReferences {
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public static void main(String[] args) {
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List<String> courses = Arrays.asList("Spring", "Spring Boot", "API", "Microservices", "AWS", "PCF", "Azure", "Docker", "Kubernetes");
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//Method Reference on Static Method
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courses.stream().map(str -> str.toUpperCase()).forEach(System.out::println);
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System.out.println("---------------");
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//Method Reference on Object of the class
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courses.stream().map(String::toUpperCase).forEach(System.out::println);
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System.out.println("---------------");
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Supplier<String> supplier = () -> new String();
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System.out.println("Empty String 1: "+supplier.get());
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//Method Reference on Constructor of the class
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Supplier<String> supplier1 = String::new;
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System.out.println("Empty String 2: "+supplier1.get());
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}
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}
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package com.ysingh.functional;
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import java.util.ArrayList;
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import java.util.Comparator;
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import java.util.List;
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import java.util.function.Predicate;
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import java.util.stream.Collectors;
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class Course {
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private String name;
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private String category;
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private int reviewScore;
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private int noOfStudents;
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public Course(String name, String category, int reviewScore, int noOfStudents) {
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super();
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this.name = name;
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this.category = category;
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this.reviewScore = reviewScore;
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this.noOfStudents = noOfStudents;
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}
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public String getCategory() {
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return category;
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}
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public void setCategory(String category) {
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this.category = category;
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}
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public int getReviewScore() {
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return reviewScore;
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}
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public void setReviewScore(int reviewScore) {
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this.reviewScore = reviewScore;
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}
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public int getNoOfStudents() {
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return noOfStudents;
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}
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public void setNoOfStudents(int noOfStudents) {
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this.noOfStudents = noOfStudents;
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}
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public String toString() {
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return name + ":" + noOfStudents + ":" + reviewScore;
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}
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}
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public class FP12CustomClass {
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public static void main(String[] args) {
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List<Course> courses = new ArrayList<>();
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courses.add(new Course("Spring", "Framework", 98, 20000));
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courses.add(new Course("Spring Boot", "Framework", 95, 18000));
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courses.add(new Course("API", "Microservices", 97, 22000));
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courses.add(new Course("Microservices", "Microservices", 96, 25000));
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courses.add(new Course("FullStack", "FullStack", 91, 14000));
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courses.add(new Course("AWS", "Cloud", 92, 21000));
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courses.add(new Course("Azure", "Cloud", 99, 21000));
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courses.add(new Course("Docker", "Cloud", 92, 20000));
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courses.add(new Course("Kubernetes", "Cloud", 91, 20000));
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Predicate<Course> reviewScoreGreaterThan90Predicate = course -> course.getReviewScore() > 90;
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Predicate<Course> reviewScoreGreaterThan95Predicate = course -> course.getReviewScore() > 95;
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Predicate<Course> reviewScoreLessThan90Predicate = course -> course.getReviewScore() < 90;
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System.out.println("All Match - reviewScoreGreaterThan90Predicate : "+courses.stream().allMatch(reviewScoreGreaterThan90Predicate));
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System.out.println("All Match - reviewScoreGreaterThan95Predicate : "+courses.stream().allMatch(reviewScoreGreaterThan95Predicate));
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System.out.println("None Match - reviewScoreLessThan90Predicate : "+courses.stream().noneMatch(reviewScoreLessThan90Predicate));
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System.out.println("Any Match - reviewScoreLessThan90Predicate : "+courses.stream().anyMatch(reviewScoreLessThan90Predicate));
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System.out.println("Any Match - reviewScoreGreaterThan95Predicate : "+courses.stream().anyMatch(reviewScoreGreaterThan95Predicate));
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Comparator<Course> comparingByNoOfStudentsIncreasing = Comparator.comparingInt(Course::getNoOfStudents);
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System.out.println(courses.stream().sorted(comparingByNoOfStudentsIncreasing).collect(Collectors.toList()));
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Comparator<Course> comparingByNoOfStudentsDecreasing = Comparator.comparingInt(Course::getNoOfStudents).reversed();
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System.out.println(courses.stream().sorted(comparingByNoOfStudentsDecreasing).collect(Collectors.toList()));
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Comparator<Course> comparingByNoOfStudentsAndNoOfReviews = Comparator.comparingInt(Course::getNoOfStudents).thenComparingInt(Course::getReviewScore).reversed();
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System.out.println(courses.stream().sorted(comparingByNoOfStudentsAndNoOfReviews).collect(Collectors.toList()));
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System.out.println(courses.stream().sorted(comparingByNoOfStudentsAndNoOfReviews).limit(5).collect(Collectors.toList()));
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System.out.println(courses.stream().sorted(comparingByNoOfStudentsAndNoOfReviews).skip(3).collect(Collectors.toList()));
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System.out.println(courses.stream().sorted(comparingByNoOfStudentsAndNoOfReviews).skip(3).limit(5).collect(Collectors.toList()));
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System.out.println(courses.stream().max(comparingByNoOfStudentsAndNoOfReviews));
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System.out.println(courses.stream().min(comparingByNoOfStudentsAndNoOfReviews));
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System.out.println(courses.stream().filter(reviewScoreLessThan90Predicate).min(comparingByNoOfStudentsAndNoOfReviews).orElse(new Course("Kubernetes", "Cloud", 91, 20000)));
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System.out.println(courses.stream().min(comparingByNoOfStudentsAndNoOfReviews).orElse(new Course("Kubernetes", "Cloud", 91, 20000)));
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System.out.println(courses.stream().filter(reviewScoreGreaterThan95Predicate).findFirst());
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System.out.println(courses.stream().filter(reviewScoreGreaterThan95Predicate).findAny());
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System.out.println(courses.stream().filter(reviewScoreGreaterThan95Predicate).mapToInt(course -> course.getNoOfStudents()).sum());
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System.out.println(courses.stream().filter(reviewScoreGreaterThan95Predicate).mapToInt(course -> course.getNoOfStudents()).average());
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System.out.println(courses.stream().filter(reviewScoreGreaterThan95Predicate).mapToInt(course -> course.getNoOfStudents()).count());
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System.out.println(courses.stream().filter(reviewScoreGreaterThan95Predicate).mapToInt(course -> course.getNoOfStudents()).max());
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System.out.println(courses.stream().filter(reviewScoreGreaterThan95Predicate).mapToInt(course -> course.getNoOfStudents()).min());
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System.out.println(courses.stream().collect(Collectors.groupingBy(Course::getCategory)));
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System.out.println(courses.stream().collect(Collectors.groupingBy(Course::getCategory, Collectors.counting())));
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System.out.println(courses.stream().collect(Collectors.groupingBy(Course::getCategory, Collectors.maxBy(Comparator.comparing(Course::getReviewScore)))));
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System.out.println(courses.stream().collect(Collectors.groupingBy(Course::getCategory, Collectors.mapping(Course::getName, Collectors.toList()))));
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}
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}

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