Java中int[]与Integer[]相互转化的方法

雨点打透心脏的1/2处 2023-01-13 04:29 171阅读 0赞

## 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);
        }
    
    }

## 小结 ##

个人认为Java 8方法最佳，即不用编写过多代码，也不用添加新依赖。

其他基本类型数组与其包装类型数组之间转换都用差不多的方法，大家可以触类旁通，举一反三。

## 参考资料 ##

1.  [Java – Convert int\[\] to Integer\[\] example][Java _ Convert int_ to Integer_ example]
2.  [ArrayUtils (Apache Commons Lang 3.11 API)][ArrayUtils _Apache Commons Lang 3.11 API]
3.  [How to convert Integer\[\] to int\[\] array in Java?][How to convert Integer_ to int_ array in Java]
4.  [How to convert int\[\] to Integer\[\] in Java?][How to convert int_ to Integer_ in Java]

[Java _ Convert int_ to Integer_ example]: https://mkyong.com/Java/java-convert-int-to-integer-example/
[ArrayUtils _Apache Commons Lang 3.11 API]: https://commons.apache.org/proper/commons-lang/javadocs/api-release/index.html
[How to convert Integer_ to int_ array in Java]: https://stackoverflow.com/questions/31394715/how-to-convert-integer-to-int-array-in-java
[How to convert int_ to Integer_ in Java]: https://stackoverflow.com/questions/880581/how-to-convert-int-to-integer-in-java