Which Among the Following Is Not Valid Data Type in Java?


Larry Thompson

When working with Java, it is essential to understand the different data types available. These data types allow us to declare variables and assign values with specific characteristics. However, not all data types are valid in Java.

Valid Data Types in Java

Before we discuss the invalid data types, let’s quickly review the valid data types in Java:

  • byte: This data type represents an 8-bit signed integer.
  • short: A short is a 16-bit signed integer.
  • int: The most commonly used integer type in Java, with a size of 32 bits.
  • long: A long is a 64-bit signed integer.
  • float: This data type represents single-precision floating-point numbers.
  • double: The double type is used for double-precision floating-point numbers.
  • char: A char represents a single Unicode character.
  • boolean:A boolean can be either true or false, representing logical values.

The Invalid Data Type

In Java, there is one particular data type that is not valid: The invalid data type in Java is “void”.

The void keyword indicates that a method does not return any value. It is often used when defining methods that perform specific actions without returning any result. However, void cannot be used as a variable type or as the return type of a function outside of method declarations.

An Example of Void Usage

To clarify the usage of void, consider the following example:

public void greet() {
    System.out.println("Hello, world!");

In this example, the greet() method does not return any value. Instead, it prints “Hello, world!”

to the console. If we attempt to assign the result of calling this method to a variable, it will result in a compilation error.


In Java, all the data types mentioned earlier are valid and commonly used for declaring variables. However, the void data type is not valid for variable declarations or as a return type outside of method definitions.

Understanding the valid and invalid data types in Java is crucial for writing error-free code and preventing compilation errors. By choosing appropriate data types for our variables and methods, we can ensure efficient memory usage and accurate program execution.

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