Java Stream - boxed() With Examples

If you want to convert a stream of primitives int, long, double to a stream of respective wrapper objects i.e. Integer, Long, Double then Java Stream API has a boxed() method to do this job.

boxed() method in Java

In Java stream API there are primitive specializations of Stream named IntStream, LongStream and DoubleStream and each of these interfaces has a boxed() method that returns a Stream consisting of the elements of this stream, each boxed to an Integer, Long or Double respectively.

So, to summarize in java.util.stream.IntStream interface there is a boxed() method that returns a Stream consisting of the elements of this stream, each boxed to an Integer.

In java.util.stream.LongStream interface there is a boxed() method that returns a Stream consisting of the elements of this stream, each boxed to a Long.

In java.util.stream.DoubleStream interface there is a boxed() method that returns a Stream consisting of the elements of this stream, each boxed to a Double.

boxed() is an intermediate operation.

boxed stream Java examples

1. If you have a Stream of ints that you want to collect to a List. It won’t be possible to directly store primitive integers into a list so you will get compile time error for the following lines of code.

IntStream intStream = IntStream.of(1, 2, 3, 4, 5);
// Not able to collect primitives to a list 
intStream.collect(Collectors.toList());

In this scenario you can use boxed() to wrap primitive ints into Integer wrapper object which can than be stored into a List.

import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class StreamBoxedDemo {
  public static void main(String[] args) {
    IntStream intStream = IntStream.of(1, 2, 3, 4, 5);
    List<Integer> numList = intStream.boxed().collect(Collectors.toList());
    System.out.println(numList);
  }
}

Output

[1, 2, 3, 4, 5]

2. Using boxed() method of LongStream to get a Stream consisting of the elements of this stream, each boxed to a Long.

public class StreamBoxedDemo {
  public static void main(String[] args) {
    List<Long> numList = LongStream.of(1, 2, 3, 4, 5)
                     .boxed().collect(Collectors.toList());
    System.out.println(numList);
  }
}

3. Using boxed() method of DoubleStream to get a Stream consisting of the elements of this stream, each boxed to a Double.

public class StreamBoxedDemo {
  public static void main(String[] args) {
    List<Double> numList = DoubleStream.of(1, 2, 3, 4, 5)
                      .boxed().collect(Collectors.toList());
    System.out.println(numList);
  }
}

That's all for this topic Java Stream - boxed() With Examples. If you have any doubt or any suggestions to make please drop a comment. Thanks!

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