Which of the following is NOT a valid data type in Java?

In Java, data types are categorized into two main groups: primitive data types and reference data types. The primitive data types include int, float, double, char, and boolean, among others. Each of these serves a specific purpose for storing simple data values.

The datatype "int" is used for storing integer values, "float" is for representing single-precision floating-point numbers, and "boolean" is used for storing true or false values. Each of these types is fundamental to programming in Java, allowing developers to define variables that suit the requirements of their applications.

In contrast, "real" is not a recognized data type in Java. The concept of a real number is encompassed within the "float" and "double" types, which can represent decimal numbers but not as a standalone data type. Therefore, the lack of "real" as a valid data type makes it distinct among the options, confirming it is the correct answer to identify as not valid in Java.