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Commit 1aabcba

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[yuvrajs] More miscellaneous examples of functional programming
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7 files changed

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‎README.md

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@@ -62,9 +62,19 @@ Functional programming is a paradigm that allows programming using expressions i
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### Using groupingBy:
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* [Example](src/main/java/com/ysingh/functional/FP12CustomClass.java)
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### Using Stream.of, Arrays.stream, IntStream, LongStream, BigInteger:
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* [Example](src/main/java/com/ysingh/functional/FP13Miscellaneous.java)
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### Using joining, flatMap:
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* [Example](src/main/java/com/ysingh/functional/FP13Miscellaneous.java)
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### Using parallelStreams:
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* [Example](src/main/java/com/ysingh/functional/FP13Miscellaneous.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 returns another stream of element called as Intermediate functions or methods or operations. They are Lazy and execute only when terminal operation is executed.
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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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* [Example](src/main/java/com/ysingh/functional/FP02CourseExcerise.java)
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### Functional Interfaces:
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A functional interface has exactly one abstract method.
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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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* [Example](src/main/java/com/ysingh/functional/FP11MethodReferences.java)
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### Higher Order Functions:
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Higher Order Function is a function which returns a function.
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* [Example](src/main/java/com/ysingh/functional/FP12CustomClass.java)
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### Java Made Easy:
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Few examples of real time Java problems that made very easy using functional programming
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* [Example](src/main/java/com/ysingh/functional/FP15JavaMadeEasy.java)

‎file.txt

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This file is to read
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This content will be read by our program
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This is very big content here

‎src/main/java/com/ysingh/functional/FP02CourseExcerise.java

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@@ -25,5 +25,11 @@ public static void main(String args[]) {
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System.out.println("Print Number of Characters for each course:");
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courses.stream().map(course -> course.length()).forEach(System.out::println);
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System.out.println();
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System.out.println("Find first course have length greater than 11 and print it in upper case:");
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System.out.println(courses.stream().peek(System.out::println).filter(course -> course.length() > 11).map(String::toUpperCase).peek(System.out::println).findFirst());
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}
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}

‎src/main/java/com/ysingh/functional/FP12CustomClass.java

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public class FP12CustomClass {
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@SuppressWarnings("unused")
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public static void main(String[] args) {
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List<Course> courses = new ArrayList<>();
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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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Predicate<Course> reviewScoreGreaterThan90Predicate2 = createPredecateReviewScore(90);
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Predicate<Course> reviewScoreGreaterThan95Predicate2 = createPredecateReviewScore(95);
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}
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//Higher Order Function
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private static Predicate<Course> createPredecateReviewScore(int cutOffReviewScore) {
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return course -> course.getReviewScore() > cutOffReviewScore;
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}
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}
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package com.ysingh.functional;
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import java.math.BigInteger;
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import java.util.Arrays;
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import java.util.List;
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import java.util.stream.Collectors;
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import java.util.stream.IntStream;
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import java.util.stream.LongStream;
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import java.util.stream.Stream;
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public class FP13Miscellaneous {
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public static void main(String[] args) {
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System.out.println("-----------------------------");
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System.out.println(Stream.of(12,9,13,5,4,2,4,12,15).count());
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System.out.println("-----------------------------");
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System.out.println(Stream.of(12,9,13,5,4,2,4,12,15).reduce(0, Integer::sum));
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System.out.println("-----------------------------");
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int[] numberArray = {12,9,13,5,4,2,4,12,15};
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System.out.println(Arrays.stream(numberArray).average());
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System.out.println("-----------------------------");
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System.out.println(Arrays.stream(numberArray).sum());
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System.out.println("-----------------------------");
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System.out.println(Arrays.stream(numberArray).min());
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System.out.println("-----------------------------");
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System.out.println(Arrays.stream(numberArray).max());
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System.out.println("-----------------------------");
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System.out.println(IntStream.range(1, 10).sum());
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System.out.println("-----------------------------");
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System.out.println(IntStream.rangeClosed(1, 10).sum());
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System.out.println("-----------------------------");
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System.out.println(IntStream.iterate(1, num -> num + 2).limit(10).peek(System.out::println).sum());
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System.out.println("-----------------------------");
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System.out.println(IntStream.iterate(2, num -> num + 2).limit(10).peek(System.out::println).sum());
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System.out.println("-----------------------------");
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System.out.println(IntStream.iterate(2, num -> num * 2).limit(10).peek(System.out::println).sum());
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System.out.println("-----------------------------");
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System.out.println(IntStream.iterate(2, num -> num * 2).limit(10).boxed().collect(Collectors.toList()));
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System.out.println("-----------------------------");
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System.out.println(LongStream.rangeClosed(1, 20).reduce(1, (num1, num2) -> num1 * num2));
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System.out.println("-----------------------------");
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System.out.println(LongStream.rangeClosed(1, 50).mapToObj(BigInteger::valueOf).reduce(BigInteger.ONE, BigInteger::multiply));
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List<String> courses = Arrays.asList("Spring", "Spring Boot", "API", "Microservices", "AWS", "PCF", "Azure", "Docker", "Kubernetes");
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List<String> courses2 = Arrays.asList("Spring", "Spring Boot", "API", "Microservices", "AWS", "PCF", "Azure", "Docker", "Kubernetes");
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System.out.println("-----------------------------");
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System.out.println(courses.stream().collect(Collectors.joining(" ")));
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System.out.println(courses.stream().collect(Collectors.joining(",")));
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System.out.println("-----------------------------");
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System.out.println(courses.stream().map(course -> course.split("")).collect(Collectors.toList()));
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System.out.println(courses.stream().map(course -> course.split("")).flatMap(Arrays::stream).collect(Collectors.toList()));
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System.out.println(courses.stream().map(course -> course.split("")).flatMap(Arrays::stream).distinct().collect(Collectors.toList()));
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System.out.println("-----------------------------");
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System.out.println(courses.stream().flatMap(course -> courses2.stream().map(course2 -> Arrays.asList(course, course2))).collect(Collectors.toList()));
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System.out.println(courses.stream().flatMap(course -> courses2.stream().map(course2 -> Arrays.asList(course, course2))).filter(list -> !list.get(0).equals(list.get(1))).collect(Collectors.toList()));
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System.out.println(courses.stream().flatMap(course -> courses2.stream().filter(course2 -> course2.length() == course.length()).map(course2 -> Arrays.asList(course, course2))).filter(list -> !list.get(0).equals(list.get(1))).collect(Collectors.toList()));
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System.out.println("-----------------------------");
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}
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}
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package com.ysingh.functional;
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import java.util.stream.LongStream;
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public class FP14Parallelizing {
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public static void main(String[] args) {
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long startTime = System.currentTimeMillis();
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System.out.println(LongStream.range(0, 1000000000).sum());
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System.out.println(System.currentTimeMillis() - startTime);
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startTime = System.currentTimeMillis();
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System.out.println(LongStream.range(0, 1000000000).parallel().sum());
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System.out.println(System.currentTimeMillis() - startTime);
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}
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}
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package com.ysingh.functional;
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import java.io.IOException;
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import java.nio.file.Files;
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import java.nio.file.Paths;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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public class FP15JavaMadeEasy {
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public static void main(String[] args) throws IOException {
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listOperations();
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fileOperations();
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threadOperations();
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}
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private static void listOperations() {
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List<String> courses = Arrays.asList("Spring", "Spring Boot", "API", "Microservices", "AWS", "PCF", "Azure", "Docker", "Kubernetes");
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List<String> modifyableCourses = new ArrayList<>(courses);
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modifyableCourses.replaceAll(str -> str.toUpperCase());
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System.out.println(modifyableCourses);
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modifyableCourses.removeIf(course -> course.length() < 6);
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System.out.println(modifyableCourses);
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}
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private static void fileOperations() throws IOException {
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System.out.println("---------------------------------");
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Files.lines(Paths.get("file.txt")).forEach(System.out::println);
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System.out.println("---------------------------------");
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Files.lines(Paths.get("file.txt")).map(str -> str.split(" ")).flatMap(Arrays::stream).distinct().sorted().forEach(System.out::println);
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System.out.println("---------------------------------");
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Files.list(Paths.get(".")).filter(Files::isDirectory).forEach(System.out::println);
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System.out.println("---------------------------------");
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}
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private static void threadOperations() {
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Runnable runnable = new Runnable() {
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@Override
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public void run() {
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for(int i=0; i<10000; i++) {
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System.out.println(Thread.currentThread().getId()+ ":" + i);
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}
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}
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};
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Thread thread1 = new Thread(runnable);
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thread1.start();
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Thread thread2 = new Thread(runnable);
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thread2.start();
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Thread thread3 = new Thread(runnable);
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thread3.start();
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Runnable runnable2 = () -> {
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for(int i=0; i<10000; i++) {
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System.out.println(Thread.currentThread().getId()+ ":" + i);
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}
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};
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Thread thread4 = new Thread(runnable2);
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thread4.start();
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Thread thread5 = new Thread(runnable2);
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thread5.start();
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Thread thread6 = new Thread(runnable2);
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thread6.start();
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}
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}

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