How to define variables in Java?

In Java, variables can be defined using keywords such as int, double, boolean, char, etc. The syntax is:

<数据类型> <变量名> = <初始值>;

Where represents the type of the variable, represents the name of the variable, and represents the initial value of the variable.

For example, define an integer variable called num with an initial value of 10.

int num = 10;

Create a string variable called ‘name’ with an initial value of “John”.

String name = "John";

Note that if you do not assign an initial value to a variable, you will need to use the keyword “null” to indicate that the variable’s initial value is null. For example, defining an empty reference variable, person:

Person person = null;