What keyword is used to define a variable in Java?

In Java, the var keyword is used to define a variable when using local variable type inference. This means that you can declare a variable without explicitly stating its data type; instead, the compiler infers the type based on the assigned value. For instance, writing var age = 30; allows the compiler to interpret age as an int.

This feature was introduced in Java 10 to simplify variable declarations while still maintaining type safety. It is important to note that var can only be used for local variables and cannot be used for fields, method parameters, or return types.

The other options provided do not pertain to Java's syntax for defining variables. While keywords like let and const are used in other programming languages like JavaScript, Java relies on specific keywords such as int, double, String, or var for variable definitions. The keyword define is not recognized in Java, making var the suitable choice in this context.