Overloading methods | part 2

"Hello, Amigo! A couple of days ago I told you about overloading methods. Did you understand everything?"

"Yes. I remember. Each class method must be unique. A member method is unique if the class has no other method with the same name and parameter types (and the order of the parameters matters)."

"Very good! I see you've learned that lesson well. Today I want to expand your knowledge in this topic just a bit. What method do you think will be called in each case?"

class Cat
{
 public static void print(int n)
 {
  System.out.println(n);
 }
 public static void print(short n)
 {
  System.out.println(n);
 }
 public static void print(Integer n)
 {
  System.out.println(n);
 }
 public static void print(String s)
 {
  System.out.println(s);
 }
public static void main(String[] args)
{
  Cat.print(1);
  Cat.print((byte)1);
  Cat.print("1");
  Cat.print(null);
 }
}

"It's hard to say."

"In the first case, 1 is an int. We have a 100% match with the method that takes an int. The first void print(int n). will be called.

In the second case, we don't have a method that takes a byte. But there are two methods that take a short and an int. Based on type widening rules, a byte will first be widened to a short, and then widened to an int. Thus, the verdict is that the void print(short n). will be called.

In the third case, we have a 100% match with the method that takes a String. The void print(String s). method will be called.

The fourth case is ambiguous. null doesn't have a specific type. The compiler will refuse to compile this code. In this case, we need to write Cat.print((Integer)null) to call the third method and Cat.print((String)null) to call the fourth."

"That was very informative. Thank you."

"I'd like to point out that when determining the correct method to call, types can only widen. They cannot narrow. Consider this example:"

class Cat
{
 public static void print(short n)
 {
  System.out.println(n);
 }
 public static void print(Integer n)
 {
  System.out.println(n);
 }

 public static void main(String[] args)
 {
  Cat.print((byte)1);
  Cat.print(1);
 }
}

In the first case, the byte type will be widened to a short and the first method will be called: void print(short n)..

In the second case, there will be an implicit widening conversion from int to Integer, and then the second method will be called: void print(Integer n)..

"I didn't expect that."

"No, here's the real surprise:"

 class Cat
{
 public static void print(Object o)
 {
  System.out.println(o);
 }
 public static void print(String s)
 {
  System.out.println(s);
 }

 public static void main(String[] args)
 {
  Cat.print(1);
  Cat.print(null);
 }
}

"Amigo, I hope you understand that in such cases it's best to specify a type cast operator (as in we did with «(byte)») in order to know exactly which method will be called."

"I never expected any problems would come from overloading methods. But then you come along. Thanks, Rishi. I'll keep up my guard on this point."

3

Task

Java Core, level 2, lesson 4

Locked

We're on overload!

It is a good thing that Java supports method overloading! It solves so many problems and gives us so much freedom! So, let's add it to your arsenal and continue to master it through practice. This time let's write two methods named print. One will print a whole number, and the other a string.

Open

3

Task

Java Core, level 2, lesson 4

Locked

int and Integer

At the end of the first quest, you learned that every primitive type in Java has a corresponding non-primitive class. Soon these non-primitives will be everywhere, mark my words! But for now, we'll write two different screen output methods: one for the primitive int and a second for the non-primitive Integer class.

Open

3

Task

Java Core, level 2, lesson 4

Locked

Freedom of the press

In CodeGym, we believe in freedom of the press. No secrets here! Write whatever you'd like, whenever you'd like. Just be sure to create special methods for it, so we can practice overloading these methods. So, write five different print methods with take different parameters. Which ones? Whatever comes to mind!

Open

3

Task

Java Core, level 2, lesson 4

Locked

Three methods and a minimum

Is it possible to compare two numbers of different types? The overwhelming majority of humans can handle this task. But for robots, it is really difficult. For them, trying to compare a double with an int would be like asking a human to compare something warm with something soft. Let's not wear out the robots: create 3 overloaded min methods using long, double, and int.

Open

3

Task

Java Core, level 2, lesson 4

Locked

Three methods and a maximum

We've once again entered the orbit of Planet Linear Chaos, home of the Ordered Isomorphs. Anyone who wants a visa must first solve a sorting and ordering problem. This time they are being very nice to you. They're giving you a super simple task: you need to create 3 methods that return the maximum of two longs, doubles, or ints.

Open