Look at the following method header: public static void myMethod(int num) Which of the following calls to the method will cause a compiler error? a) myMethod(7); b) myMethod(6.2); c) long x = 99; myMethod(x); d) short s = 2; myMethod(s);

Understanding Java data types is essential for programming in Java, as they determine the kind and size of data that can be stored and manipulated within your code. In Java, there are two main data type categories: primitive and reference.

Primitive data types include int, long, short, double, and so on. These types represent single values and are not objects. For example, an int can store whole numbers without any decimals, while a double can store large and small numbers with decimal points.

Reference types, on the other hand, include classes, arrays, and interfaces. These reference an object or an instance rather than hold a value directly. For instance, a variable of type String holds the reference of a string object instead of the string characters themselves.

Understanding these types is crucial when defining methods and passing parameters, as mismatched data types between method arguments and parameters can lead to compiler errors. For instance, trying to pass a double to a method expecting an int parameter is problematic without explicit casting because the types are not automatically compatible.

Method overloading in Java is a feature that allows multiple methods to have the same name within a class, but with different parameters—either in type, number, or both. This concept is a cornerstone of Java's polymorphism and is useful for defining methods that should perform similar actions with different types of input.

For example, you could overload a method calculateSum to accept either two int parameters or two double parameters. When you call this method, Java determines which version to use based on the data types of the arguments passed.

Example:

• public int calculateSum(int a, int b)
• public double calculateSum(double a, double b)

Despite having the same method name, each method deals with different types of data. The Java compiler identifies which method to call at compile-time, ensuring type safety and reducing potential errors during runtime.

Automatic type conversion, also known as type promotion, in Java happens when one type of data is automatically converted into another type in certain contexts. This typically occurs within expressions or assignments where the types are compatible and the size of the target type is larger than that of the source.

For instance, if you assign an int value to a long variable, Java will automatically convert the int to a long. However, when dealing with larger to smaller types, like from long to int, explicit casting is required because information might be lost and the conversion is not performed automatically.

Automatic type conversions also occur in method invocations when the provided argument type is smaller than the parameter's type. For instance, calling a method with an int parameter with a short argument is valid since short can be automatically promoted to int. Conversely, passing a double to an int parameter causes an error because double is not automatically converted to int due to potential loss of precision.

As a best practice, developers should be aware of these conversions to avoid unintended behavior and compiler errors, ensuring clear and accurate code.