Parameters & Arguments

When we are writing methods in our code, we may need to provide some input to our methods. This allows our method to perform the same action using different data each time, making them much more flexible. So, let’s look at how to do that in theory and discuss some of the terminology we’ll need to understand first.

Parameters

When we define a method, we can also list a number of parameters, or inputs, that the method can accept. Depending on the language we are using, we may need to provide either a name, or possibly a type and a name for each parameter. In addition, many languages allow us to accept variable length parameters, which we’ll cover in detail later in this module.

So, in our code, we can define a method that accepts parameters in this way:

public static void foo(String parameter1, String parameter2){
    System.out.println(parameter1);
    System.out.println(parameter2);
}

Typically, each parameter is listed in the method’s definition. So, this example defines a method named foo that accepts two parameters, parameter1 and parameter2. Together, they make up the method’s signature, which allows our programs to find them. Therefore, no two methods may share the same signature. Instead, they must either use a different name, or a different number of parameters. In statically typed languages such as Java, we can also vary the types of each parameter instead, not just the number of parameters.

Arguments

Of course, when we want to call a method in our code, we must provide values for each parameter. Those values are known as arguments to the method. In code, it might look something like this:

public static void main(String[] args){
    foo("abc", "xyz");
}

In that example, we see foo("abc", "xyz"), which is calling our method named foo. Inside, it provides two arguments, one for each parameter of the method. So, inside of our method, the variable parameter1 will be "abc", and parameter2 will be "xyz". Pretty straightforward, right?