Given some object o, I need to find its dimensionality (eg: for int[x][y][z] the dimensionality is 3), I figured that any appropriate method would be in the class of the object.
int dimensionality = o.getClass().getName().indexOf('L');
works, but its source refers to a native method, so I'm left getting the answer from a string, rather than directly.
If anyone knows a better way of doing this it would be appreciated (although more for the sake of curiosity than necessity).
Here's a recursive solution using Class.isArray:
static int getDimensionality(final Class<?> type) {
if (type.isArray()) {
return 1 + getDimensionality(type.getComponentType());
}
return 0;
}
public static void main (String[] args) {
System.out.println(getDimensionality(int.class)); // 0
System.out.println(getDimensionality(int[].class)); // 1
System.out.println(getDimensionality(int[][].class)); // 2
System.out.println(getDimensionality(int[][][].class)); // 3
}
Although as PM 77-1 points out, this is not truly a measure of dimensionality but of the depth of a jagged array in terms of its static type. There are no true multidimensional arrays in Java, just arrays of arrays.
If the array is more complex e.g.
Object[] oa = new Object[] {1, new Object[] {"a", new int[] {5, 6, 7}, "c"}, 3};
getComponentType is not gonna work. In that case you could determine the maximum nesting depth like this
static int maxDim(Object[] oa) {
int maxDim = 0;
for(Object o: oa) {
if(o instanceof int[] || o instanceof long[] || o instanceof short[] ||
o instanceof byte[] || o instanceof float[] ||
o instanceof double[] || o instanceof boolean[]) {
maxDim = Math.max(maxDim, 1);
} else if(o instanceof Object[]) {
maxDim = Math.max(maxDim, maxDim((Object[])o));
}
}
return maxDim + 1;
}
oa[1] is of type Object, not int[]. Even though oa[1] refers to an int[], one cannot subscript the inner array without typecasting oa[1] to int[] first.
{{{},{}},{}}?arrayis just anotherarray. There's nothing here to argue about.