In Javascript you write a function like:
function hypotenuse(a, b) {
return Math.sqrt(a ** 2 + b ** 2);
}function tells us it’s a function
hypotenuse is the name.
a and b are parameters.
And the body is enclosed in {}s.
In Java we call it a method and write it like:
double hypotenuse(double a, double b) {
return Math.sqrt(Math.pow(a, 2) + Math.pow(b, 2));
}The first double is the return type
The parameters a and b also need types.
The body is basically the same but there’s no ** in Java.
Just like variables in Java need to be declared with their type a method needs to be declared with a return type that tells the compiler what kind of value the method returns.
This is how Java can statically check whether code like this is legal or not:
int x = someMethod();For the compiler to know that’s okay I needs to know whether someMethod() returns an int or not.
Method parameters are just another kind of variable and all variables in Java have a declared type.
This lets Java statically check whether this is okay or not:
someOtherMethod(10, 20.0);If the first parameter was declared to be an int and the second to be a double, everything is fine.