What are the rules for defining arrays in Java?

In Java, the rules for defining arrays include the following aspects:

1. When defining an array, it is necessary to specify the type of elements that will be stored in the array. For example, you can define an array of integers, an array of strings, and so on.
2. The size of an array: When defining an array, it is necessary to specify the size of the array, which refers to the number of elements the array can hold. The size of an array is fixed and cannot be changed once defined.
3. Name of array: When defining an array, it is necessary to name the array so it can be used later. The name of the array can be customised according to requirements.
4. When defining an array, you can specify its initial values and assign values to the array in subsequent code. Array elements can be either primitive values or objects.

Here are some examples of array definitions:

// 定义一个整数类型的数组，大小为5
int[] numbers = new int[5];

// 定义一个字符串类型的数组，大小为3，同时初始化数组的元素
String[] names = {"Alice", "Bob", "Charlie"};

// 定义一个二维数组，大小为3x3
int[][] matrix = new int[3][3];

It is important to note that in Java, array indexes start at 0, meaning the index of the first element is 0, the index of the second element is 1, and so on.