How to cast from List to double[] in Java?

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With java-8, you can do it this way.

double[] arr = frameList.stream().mapToDouble(Double::doubleValue).toArray(); //via method reference
double[] arr = frameList.stream().mapToDouble(d -> d).toArray(); //identity function, Java unboxes automatically to get the double value

What it does is :

  • get the Stream<Double> from the list
  • map each double instance to its primitive value, resulting in a DoubleStream
  • call toArray() to get the array.

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