Java Arrays.equals() returns false for two dimensional arrays

I was just curious to know - why does Arrays.equals(double[][], double[][]) return false? when in fact the arrays have the same number of elements and each element is the same?

For example I performed the following test.

double[][] a,  b;
int size =5;

a=new double[size][size];
b=new double[size][size];

for( int i = 0; i < size; i++ )
    for( int j = 0; j < size; j++ ) {
        a[i][j]=1.0;
        b[i][j]=1.0;
    }

if(Arrays.equals(a, b))
    System.out.println("Equal");
else
    System.out.println("Not-equal");

Returns false and prints "Not-equal".

on the other hand, if I have something like this:

double[] a,  b;
int size =5;

a=new double[size];
b=new double[size];

for( int i = 0; i < size; i++ ){
    a[i]=1.0;
    b[i]=1.0;
} 

if(Arrays.equals(a, b))
    System.out.println("Equal");
else
    System.out.println("Not-equal");

returns true and prints "Equal". Does the method only work with single dimensions? if so, is there something similar for multi-dimensional arrays in Java?