Java8Samples.java

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package demo;

import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

/**
 *
 * @author madhub
 */
public class Java8Samples {

    public static void main(String[] args) {
        List<String> names = Arrays.asList("Rachel Green", "Monica Geller", "Phoebe Buffay", 
        "Joey Tribbiani", " Chandler Bing", " Ross Geller ");
        

        // create list of string
        List<String> nCopies = Collections.nCopies(10, "Google")
                                            .forEach(value -> System.out.println(value));

        // on any collection , you can use foreach
        names.forEach(value -> System.out.println(value));
        // or
        names.forEach(System.out::println);
        // or

        // Removes all of the elements of this collection that satisfy the given predicate
        //names.removeIf(name -> name.contains("ll"));
        //  Replaces each element of this list with the result of applying the operator to that element
        names.replaceAll(name -> name + ",");

        Map<String, Integer> authorBooks = new HashMap<String, Integer>();
        authorBooks.put("Robert Ludlum", 27);
        authorBooks.put("Clive Cussler", 50);
        authorBooks.put("Tom Clancy", 17);
        authorBooks.forEach((a, b) -> System.out.println(a + " wrote " + b + " books"));
        
        Integer orDefault = authorBooks.getOrDefault("AuthorA", 0);

        
        
        Stream<Double> generate = Stream.generate(() -> Math.random());
        generate.limit(5).forEach(System.out::println);

        System.out.println("");

    }

    public static void moreLambdaSamples() {

        Arrays.asList("a1", "a2", "a3")
                .stream()
                .findFirst()
                .ifPresent(System.out::println);  // a1

        // Stream.of() to create a stream from a bunch of object references.
        Stream.of("a1", "a2", "a3")
                .findFirst()
                .ifPresent(System.out::println);  // a1
        
        // Java 8 ships with special kinds of streams for working with the primitive data types int, long and double
        IntStream.range(1, 4)
                .forEach(System.out::println);

        Arrays.stream(new int[]{1, 2, 3})
                .map(n -> 2 * n + 1)
                .average()
                .ifPresent(System.out::println);  // 5.0

        //  transform a regular object stream to a primitive stream or vice versa. 
        // For that purpose object streams support the special mapping operations mapToInt(), mapToLong() and mapToDouble:
        Stream.of("a1", "a2", "a3")
                .map(s -> s.substring(1))
                .mapToInt(Integer::parseInt)
                .max()
                .ifPresent(System.out::println);  // 3

        Stream.of("d2", "a2", "b1", "b3", "c")
                .sorted((s1, s2) -> {
                    System.out.printf("sort: %s; %s\n", s1, s2);
                    return s1.compareTo(s2);
                })
                .filter(s -> {
                    System.out.println("filter: " + s);
                    return s.startsWith("a");
                })
                .map(s -> {
                    System.out.println("map: " + s);
                    return s.toUpperCase();
                })
                .forEach(s -> System.out.println("forEach: " + s));

        parallelStreamDemo();

    }

    public static void parallelStreamDemo() {
        Arrays.asList("a1", "a2", "b1", "c2", "c1")
                .parallelStream()
                .filter(s -> {
                    System.out.format("filter: %s [%s]\n",
                            s, Thread.currentThread().getName());
                    return true;
                })
                .map(s -> {
                    System.out.format("map: %s [%s]\n",
                            s, Thread.currentThread().getName());
                    return s.toUpperCase();
                })
                .forEach(s -> System.out.format("forEach: %s [%s]\n",
                                s, Thread.currentThread().getName()));
    }
}