Functions

Defining and calling functions

In Java, a function is called a method. You can define a method by specifying its name, return type, and parameters. Here's an example:

public class MethodExample {
    public static int add(int x, int y) {
        return x + y;
    }

    public static void main(String[] args) {
        int sum = add(1, 2);
        System.out.println(sum);
    }
}

In the above example, we define a method called add that takes two integer parameters x and y, and returns their sum. We call the add method in the main method, passing in the arguments 1 and 2. The add method returns the sum of the two arguments, which we assign to the sum variable. We then print the value of sum to the console.

Parameters and return values

Methods in Java can have zero or more parameters, and can return a value or be void (i.e. not return anything). Here's an example of a method with no parameters and no return value:

public class VoidMethodExample {
    public static void sayHello() {
        System.out.println("Hello!");
    }

    public static void main(String[] args) {
        sayHello();
    }
}

In the above example, we define a method called sayHello that takes no parameters and returns nothing (i.e. void). We call the sayHello method in the main method, which prints "Hello!" to the console.

Here's an example of a method with multiple parameters and a return value:

public class MaxMethodExample {
    public static int max(int x, int y) {
        if (x > y) {
            return x;
        } else {
            return y;
        }
    }

    public static void main(String[] args) {
        int result = max(3, 7);
        System.out.println(result);
    }
}

In the above example, we define a method called max that takes two integer parameters x and y, and returns the larger of the two values. We call the max method in the main method, passing in the arguments 3 and 7. The max method compares the two arguments and returns the larger value, which we assign to the result variable. We then print the value of result to the console.

Function overloading

In Java, you can define multiple methods with the same name but different parameter types or numbers. This is called function overloading. Here's an example:

public class OverloadExample {
    public static int add(int x, int y) {
        return x + y;
    }

    public static double add(double x, double y) {
        return x + y;
    }

    public static void main(String[] args) {
        int sum1 = add(1, 2);
        double sum2 = add(1.5, 2.5);
        System.out.println(sum1);
        System.out.println(sum2);
    }
}

In the above example, we define two methods called add with different parameter types (integers and doubles). We call the add method with integer arguments in the first call, and with double arguments in the second call. The Java compiler selects the appropriate method based on the argument types, allowing us to use the same method name for different types of calculations.

That's an overview of functions (methods) in Java, including defining and calling methods, parameters and return values, and function overloading. Functions are a fundamental building block of Java programming, allowing you to write reusable code and break up complex programs into smaller, more manageable pieces.