多维长度数组反射java

Question

如何在java上找到带有反射的多维数组的长度？

Answer 1

There is no such thing as "length" for multi-dimensional array; it may not be rectangular. I'm guessing you're talking about the number of dimensions. You need to descend into it iteratively and count.

public int getDimensionCount(Object array) {
  int count = 0;
  Class arrayClass = array.getClass();
  while ( arrayClass.isArray() ) {
    count++;
    arrayClass = arrayClass.getComponentType();
  }
  return count;
}

Answer 2

Java arrays have lengths per instance, not all arrays in the same dimension have to have equals lengths. That said, you can get the lengths of instances in the.

Dimensions can be counted by the number of '[' in their name, this is quicker than descending the type hierarchy. The following code:

        int[][][] ary = {{{0},{1}}};

        Class cls = ary.getClass();

        boolean isAry = cls.isArray();
        String clsName = cls.getName();

        System.out.println("is array=" + isAry);
        System.out.println("name=" + clsName);

        int nrDims = 1 + clsName.lastIndexOf('[');

        System.out.println("nrDims=" + nrDims);

        Object orly = ary;

        for (int n = 0; n < nrDims; n++) {

            int len = Array.getLength(orly);

            System.out.println("dim[" + n + "]=" + len);

            if (0 < len) {
                orly = Array.get(orly, 0);
            }
        }

gives the following output:

is array=true
name=[[[I
nrDims=3
dim[0]=1
dim[1]=2
dim[2]=1

Answer 3

Class clazz = Class.forName("ReflectionTest");    
Method m = clazz.getDeclaredMethod("getArray");
Object o1 = m.invoke(o, arg);
int array[][] = (int[][])o1;
System.out.println("Array length: " + array.length);
System.out.println("Array length: " + array[0].length);

Answer 4

使用java.lang.reflect.Array.getLength(obj) 。

Answer 5

If you like me were trying to get the number of dimensions and the size of them then:

private static int[] getDimentionsOf(final Object expectedArray) {
    if (!expectedArray.getClass().isArray()) {
        return new int[0];
    }
    final int dimensionSize = Array.getLength(expectedArray);
    final int[] innerDimensions =
                    (expectedArray.getClass().getComponentType().isArray())
                                    ? getDimentionsOf(Array.get(expectedArray, 0))
                                    : new int[0];
    final int lenghtPlusOne = innerDimensions.length + 1;
    final int[] newDimensions = new int[lenghtPlusOne];
    System.arraycopy(innerDimensions, 0, newDimensions, 1, innerDimensions.length);
    newDimensions[0] = dimensionSize;
    return newDimensions;
}