Convert Integer[] to int[] array

问题

Is there a fancy way to cast an Integer array to an int array? (I don't want to iterate over each element; I'm looking for an elegant and quick way to write it)

The other way around I'm using

scaleTests.add(Arrays.stream(data).boxed().toArray(Double[]::new));

I'm looking for an one-liner but wasn't able to find something.

The goal is to:

int[] valuesPrimitives = <somehow cast> Integer[] valuesWrapper

回答1:

You can use Stream APIs of Java 8

int[] intArray = Arrays.stream(array).mapToInt(Integer::intValue).toArray();

回答2:

If you can consider using Apache commons ArrayUtils then there is a simple toPrimitive API:

public static double[] toPrimitive(Double[] array, double valueForNull)

Converts an array of object Doubles to primitives handling null. This method returns null for a null input array.

回答3:

Using Guava, you can do the following:

int[] intArray = Ints.toArray(intList);

If you're using Maven, add this dependency:

<dependency>
   <groudId>com.google.guava</groupId>
   <artifactId>guava</artifactId>
   <version>18.0</version>
</dependency>

回答4:

If you have access to the Apache lang library, then you can use the ArrayUtils.toPrimitive(Integer[]) method like this:

int[] primitiveArray = ArrayUtils.toPrimitive(objectArray);

来源：https://stackoverflow.com/questions/31394715/convert-integer-to-int-array

标签

java

arrays

java-8

wrapper