JAVA EE: Why is Java 8 Stream required? | Java 8 streams tutorial | Java 8 streams

Wednesday 30 August 2017

Why is Java 8 Stream required? | Java 8 streams tutorial | Java 8 streams | Streams in Java 8

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Why is Java 8 Stream required? | Java 8 streams tutorial | Java 8 streams | Streams in Java 8

NonStreamDemo.java

import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

/**
 * Before JDK8
 * 
 * We want to iterate over a list of integers and find out sum
 * of all the integers greater than 10.
 * 
 */
public class NonStreamDemo
{
    public static void main(String[] args)
    {

        List<Integer> numberList = Arrays.asList(2, 5, 10, 20, 50);
        int sum = calculateSum(numberList);
        System.out.println("sum = " + sum);
    }

    private static int calculateSum(List<Integer> list)
    {
        Iterator<Integer> it = list.iterator();
        int sum = 0;
        while (it.hasNext())
        {
            int num = it.next();
            if (num > 10)
            {
                sum += num;
            }
        }
        return sum;
    }
}

Output

sum = 70

StreamDemo.java

import java.util.Arrays;
import java.util.List;

/**
 * With JDK8
 * 
 * We want to iterate over a list of integers and find out sum
 * of all the integers greater than 10.
 * 
 */
public class StreamDemo
{
    public static void main(String[] args)
    {

        List<Integer> numberList = Arrays.asList(2, 5, 10, 20, 50);
        int sum = calculateSum(numberList);
        System.out.println("sum = " + sum);
    }

    private static int calculateSum(List<Integer> list)
    {
        return list.stream().filter(i -> i > 10).mapToInt(i -> i).sum();
    }
}