Java 8 Streams - Stream.mapToInt Examples

package com.logicbig.example.stream;

import java.util.IntSummaryStatistics;
import java.util.stream.IntStream;
import java.util.stream.Stream;

public class MapToIntExample {

    public static void main(String... args) {
        String[] s = {"one", "two", "three", "four"};
        Stream<String> stringStream = Stream.of(s);
        IntStream intStream = stringStream.mapToInt(e -> e.length());
        IntSummaryStatistics stats = intStream.peek(System.out::println)
                                              .summaryStatistics();
        System.out.println(stats);
    }
}

package com.logicbig.example;

import java.util.Arrays;
import java.util.stream.Stream;

/**
 * Even though this is thread safe, but the result is non-deterministic
 */
public class SideEffectWrongUse2Fix {
    public static void main(String[] args) {

        int[] lengths = Stream.of("Banana", "Pear", "Apple")
                              .peek(SideEffectWrongUse2Fix::longTask)//applying side effect
                              .parallel()
                              .mapToInt(s -> s.length())
                              .toArray();
        System.out.println(Arrays.toString(lengths));
    }

    private static void longTask(String s) {
        try {//some stateless task simulation. e.g. sending email
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

package com.logicbig.example;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.stream.Stream;

/**
 * Even though this is thread safe, but the result is non-deterministic
 */
public class SideEffectWrongUse2 {
    public static void main (String[] args) {
        List<Integer> lengths = Collections.synchronizedList(new ArrayList<>());
        Stream.of("Banana", "Pear", "Apple")
              .peek(SideEffectWrongUse2::longTask)//applying side effect
              .parallel()
              .mapToInt(s -> s.length())
              .forEach(lengths::add);//collecting via side effect
                                    // updating state
        System.out.println(lengths);
    }

    private static void longTask (String s) {
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}