Java中int[]与Integer[]相互转化的方法-蒲公英云

Java中int[]与Integer[]相互转化的方法

传统方法

//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 工具类 ArrayUtils

添加依赖

<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()与ArrayUtils.toPrimitive()源码如下：

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);
    }
}