傳統方法

//Convert int[] to Integer[] public static Integer[] toObject(int[] intArray) {Integer[] result = new Integer[intArray.length];for (int i = 0; i < intArray.length; i++) {result[i] = Integer.valueOf(intArray[i]);}return result; }//Convert Integer[] to int[] public static int[] toPrimitive(Integer[] IntegerArray) {int[] result = new int[IntegerArray.length];for (int i = 0; i < IntegerArray.length; i++) {result[i] = IntegerArray[i].intValue();}return result; }

Apache Commons Lang 工具類 ArrayUtils

添加依賴

<dependency><groupId>org.apache.commons</groupId><artifactId>commons-lang3</artifactId><version>3.12.0</version> </dependency> import org.apache.commons.lang3.ArrayUtils;public class ArrayConvertExample {public static void main(String[] args) {int[] obj = new int[] { 1, 2, 3 };Integer[] newObj = ArrayUtils.toObject(obj);Integer[] obj2 = new Integer[] { 4, 5, 6 };int[] newObj2 = ArrayUtils.toPrimitive(obj2);Integer[] obj3 = new Integer[] { 7, 8, null };int[] newObj3 = ArrayUtils.toPrimitive(obj2, 0);} }

ArrayUtils.toObject()與ArrayUtils.toPrimitive()源碼如下：

package org.apache.commons.lang3;public class ArrayUtils {...public static final Integer[] EMPTY_INTEGER_OBJECT_ARRAY = new Integer[0];//Convert int[] to Integer[]public static Integer[] toObject(final int[] array) {if (array == null) {return null;} else if (array.length == 0) {return EMPTY_INTEGER_OBJECT_ARRAY;}final Integer[] result = new Integer[array.length];for (int i = 0; i < array.length; i++) {result[i] = Integer.valueOf(array[i]);}return result;}public static final int[] EMPTY_INT_ARRAY = new int[0];//Convert Integer[] to int[]public static int[] toPrimitive(final Integer[] array) {if (array == null) {return null;} else if (array.length == 0) {return EMPTY_INT_ARRAY;}final int[] result = new int[array.length];for (int i = 0; i < array.length; i++) {result[i] = array[i].intValue();}return result;}public static int[] toPrimitive(final Integer[] array, final int valueForNull) {if (array == null) {return null;} else if (array.length == 0) {return EMPTY_INT_ARRAY;}final int[] result = new int[array.length];for (int i = 0; i < array.length; i++) {final Integer b = array[i];result[i] = (b == null ? valueForNull : b.intValue());}return result;}...}

Java 8 方法

import java.util.Arrays; import java.util.stream.IntStream;public class ArrayConvertExample {public static void main(String[] args) {Integer[] obj = new Integer[] {null, 1, 2, 3};int[] newObj = Arrays.stream(obj).mapToInt(i -> i == null ? 0 : i.intValue()).toArray();//Integer[] obj = new Integer[] {1, 2, 3};//int[] newObj = Arrays.stream(obj).mapToInt(Integer::valueOf).toArray();int[] obj2 = new int[] {4, 5, 6};Integer[] newObj2 = Arrays.stream(obj2).boxed().toArray(Integer[]::new);Integer[] newObj3 = IntStream.of(obj2).boxed().toArray(Integer[]::new);}}

小結

個人認為Java 8方法最佳，即不用編寫過多代碼，也不用添加新依賴。

其他基本類型數組與其包裝類型數組之間轉換都用差不多的方法，大家可以觸類旁通，舉一反三。

參考資料

Java – Convert int[] to Integer[] example

ArrayUtils (Apache Commons Lang 3.11 API)

How to convert Integer[] to int[] array in Java?

How to convert int[] to Integer[] in Java?

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