Lesson 5: Method Definitions

You've now called a number of methods, like Math.max(2.0, 3.0);, but how would you define such a method?

(This method returns the larger of the two numbers you pass in, by the way. In this example, it would return 3.0.)

A little bit like this:

public class Math {
  public static double max(double a, double b) {
    if (a > b) {
      return a;
    }
    return b;
  }
}

Let's break this down.

Method Signature

The method's signature is the following: public static double max(double a, double b)

The signature says what the method takes, and what the method returns, along with other information that we'll cover later.

1. public: This means that the method can be called outside of the Math

   class. We'll cover this more in chapter 6.

2. static: We'll cover this more in chapter 6.

3. double: This method returns a double. This can be any data type (int,

   String, etc.) or void, which means that the method returns nothing.

4. max(double a, double b): The method is called max, and takes two

   parameters: a, which is a double, and b which is also a double.

Return Keyword

There's another new piece of syntax here: the return keyword. The idea is that when you return, the method immediately exits at that point. If the return type of your method is void, you can just do return;. If the return type is not void, you must return something of the appropriate data type. E.g. if your return type is double, this will work: return 3.1;, but this will not: return "foo";.

Conclusion

Here are your PracticeIt problems:

1. Method call and signature error correction

2. Method call and return value error correction