In Java, there are two types of arrays:

1. Single-dimensional arrays: These are arrays that have a single dimension, similar to a list. They are declared using the square brackets [] after the data type. For example:

int[] numbers;

2. Multi-dimensional arrays: These are arrays that have more than one dimension. They are declared using multiple sets of square brackets. For example:

int[][] numbers;

This declares a 2-dimensional array of integers. You can have arrays with more than two dimensions as well, such as a 3-dimensional array:

int[][][] numbers;

Arrays in Java are dynamically allocated, which means that their size is not fixed and can be changed at runtime. They are also zero-indexed, meaning that the first element of the array is at index 0, the second element is at index 1, and so on.

Arrays in Java are useful for storing and manipulating large amounts of data in a structured manner. They provide various methods for manipulating the elements of the array, such as sorting, searching, and inserting or deleting elements. However, arrays have a fixed size, which means that once you create an array, you cannot change its size unless you create a new array and copy the elements of the old array into the new one.