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Java 8 Streams - Stream.mapToDouble Examples

[Last Updated: Nov 8, 2025]

Java 8 Streams Java Java API 

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Interface:

java.util.stream.Stream

java.lang.AutoCloseableAutoCloseablejava.util.stream.BaseStreamBaseStreamjava.util.stream.StreamStreamLogicBig

Method:

DoubleStream mapToDouble(ToDoubleFunction<? super T> mapper)

This intermediate operation returns a DoubleStream consisting of the results of applying the given mapper function to the elements of this stream.


Examples


package com.logicbig.example.stream;

import java.util.stream.DoubleStream;
import java.util.stream.Stream;

public class MapToDoubleExample {

    public static void main(String... args) {
        String[] s = {"1.1", "2.4", "3.7", "4.33"};
        Stream<String> stringStream = Stream.of(s);
        DoubleStream doubleStream = stringStream.mapToDouble(Double::parseDouble);
        double sum = doubleStream.peek(System.out::println)
                                 .sum();
        System.out.println("sum: " + sum);
    }
}

Output

1.1
2.4
3.7
4.33
sum: 11.530000000000001

See Also