9- Generic Methods

Jun 20, 2026 06:32 · 4:48 · English · Whisper Turbo · 2 speakers

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Lecture Index

0:03

S… Speaker 2 (9- Generic Methods)

So you have learned how to create generic classes.

0:05

S… Speaker 2 (9- Generic Methods)

Now in this generic class we have a couple of generic methods add

0:09

S… Speaker 2 (9- Generic Methods)

and get,

0:10

S… Speaker 2 (9- Generic Methods)

but we can also declare a generic method inside a non generic

0:14

S… Speaker 1 (9- Generic Methods)

class.

0:15

S… Speaker 1 (9- Generic Methods)

Let me show you.

0:16

S… Speaker 2 (9- Generic Methods)

So let's add a new class to this package.

0:19

S… Speaker 1 (9- Generic Methods)

We're going to call it utils.

0:21

S… Speaker 2 (9- Generic Methods)

This class is going to have a bunch of utility methods.

0:26

S… Speaker 2 (9- Generic Methods)

Now, let's say we want to get the maximum of two values.

0:29

S… Speaker 2 (9- Generic Methods)

So here we can add a public method.

0:31

S… Speaker 2 (9- Generic Methods)

We make it static so we don't have to create an instance of the utils class.

0:35

S… Speaker 2 (9- Generic Methods)

This is a common convention for declaring utility methods.

0:39

S… Speaker 2 (9- Generic Methods)

We make them static.

0:40

S… Speaker 2 (9- Generic Methods)

Now we return an integer,

0:41

S… Speaker 2 (9- Generic Methods)

we call the method max and give it two parameters,

0:44

S… Speaker 2 (9- Generic Methods)

first and second.

0:46

S… Speaker 2 (9- Generic Methods)

Here we can use the ternary operator to return the

0:50

S… Speaker 2 (9- Generic Methods)

maximum of these two values.

0:52

S… Speaker 1 (9- Generic Methods)

So we return,

0:53

S… Speaker 2 (9- Generic Methods)

here we have a boolean expression.

0:56

S… Speaker 2 (9- Generic Methods)

if first is greater than the second,

0:58

S… Speaker 1 (9- Generic Methods)

return first,

1:01

S… Speaker 2 (9- Generic Methods)

otherwise return second.

1:02

S… Speaker 1 (9- Generic Methods)

Pretty simple,

1:04

S… Speaker 1 (9- Generic Methods)

right? Now,

1:05

S… Speaker 2 (9- Generic Methods)

we want to make this method generic.

1:06

S… Speaker 2 (9- Generic Methods)

So instead of getting two integers and returning an integer,

1:09

S… Speaker 2 (9- Generic Methods)

you want to be able to work with different types of objects.

1:12

S… Speaker 2 (9- Generic Methods)

Now we don't necessarily have to make this class generic,

1:15

S… Speaker 2 (9- Generic Methods)

we can declare a generic method inside a non -generic class.

1:19

S… Speaker 1 (9- Generic Methods)

Let me show you.

1:20

S… Speaker 1 (9- Generic Methods)

So,

1:21

S… Speaker 2 (9- Generic Methods)

just before the return type,

1:24

S… Speaker 2 (9- Generic Methods)

we add the generic type parameter.

1:26

S… Speaker 2 (9- Generic Methods)

Okay, now we replace all these integers with T.

1:30

S… Speaker 2 (9- Generic Methods)

So here's the return type and the two parameters.

1:34

S… Speaker 1 (9- Generic Methods)

We have a compilation error because

1:38

S… Speaker 2 (9- Generic Methods)

we cannot apply the comparison operator between objects of type T.

1:42

S… Speaker 2 (9- Generic Methods)

We can only apply it to numbers and characters.

1:46

S… Speaker 1 (9- Generic Methods)

So how can we compare these two objects?

1:48

S… Speaker 1 (9- Generic Methods)

Well,

1:49

S… Speaker 2 (9- Generic Methods)

you learned about the comparable interface in the last video.

1:52

S… Speaker 2 (9- Generic Methods)

So here we can tell the Java compiler that this T is an

1:56

S… Speaker 2 (9- Generic Methods)

object that implements the comparable interface.

1:59

S… Speaker 1 (9- Generic Methods)

How can we do that?

2:01

S… Speaker 1 (9- Generic Methods)

We type extends comparable of T.

2:05

S… Speaker 1 (9- Generic Methods)

So we are applying a constraint.

2:07

S… Speaker 1 (9- Generic Methods)

Now,

2:08

S… Speaker 1 (9- Generic Methods)

when we type first dot,

2:12

S… Speaker 2 (9- Generic Methods)

we see that this object has a method called compare to,

2:16

S… Speaker 2 (9- Generic Methods)

which takes an object of type T.

2:18

S… Speaker 2 (9- Generic Methods)

So we can compare first with second.

2:21

S… Speaker 2 (9- Generic Methods)

If it's less than zero,

2:23

S… Speaker 1 (9- Generic Methods)

then we're going to return second,

2:27

S… Speaker 2 (9- Generic Methods)

otherwise we're going to return first.

2:29

S… Speaker 2 (9- Generic Methods)

So this is one application of the compareTo method.

2:33

S… Speaker 1 (9- Generic Methods)

Now let's test this method.

2:35

S… Speaker 2 (9- Generic Methods)

So, back to the main class,

2:37

S… Speaker 1 (9- Generic Methods)

here we type utils dot,

2:40

S… Speaker 2 (9- Generic Methods)

we call the max method.

2:42

S… Speaker 1 (9- Generic Methods)

Now look at the type of this parameter,

2:44

S… Speaker 1 (9- Generic Methods)

it's t,

2:45

S… Speaker 2 (9- Generic Methods)

because at this point the Java compiler doesn't know if

2:49

S… Speaker 2 (9- Generic Methods)

we're going to pass an integer,

2:50

S… Speaker 1 (9- Generic Methods)

a character,

2:51

S… Speaker 1 (9- Generic Methods)

a string,

2:52

S… Speaker 2 (9- Generic Methods)

a user object,

2:52

S… Speaker 1 (9- Generic Methods)

or what.

2:53

S… Speaker 2 (9- Generic Methods)

Now, the moment I pass a value here,

2:56

S… Speaker 1 (9- Generic Methods)

let's say 1,

2:57

S… Speaker 2 (9- Generic Methods)

the Java compiler knows this is an integer,

3:00

S… Speaker 2 (9- Generic Methods)

so it wraps it inside the integer class,

3:03

S… Speaker 2 (9- Generic Methods)

and it knows that the second parameter should also be an integer.

3:06

S… Speaker 2 (9- Generic Methods)

So I cannot pass a character or a string here.

3:09

S… Speaker 1 (9- Generic Methods)

This is the benefit of using generics.

3:11

S… Speaker 2 (9- Generic Methods)

Instead of adding two parameters of type object,

3:14

S… Speaker 2 (9- Generic Methods)

we use a generic method.

3:16

S… Speaker 1 (9- Generic Methods)

Okay?

3:17

S… Speaker 1 (9- Generic Methods)

Now,

3:18

S… Speaker 1 (9- Generic Methods)

back in the main class.

3:20

S… Speaker 2 (9- Generic Methods)

So let's pass 3,

3:22

S… Speaker 2 (9- Generic Methods)

this will return the max we store it here and then print it

3:26

S… Speaker 2 (9- Generic Methods)

on the console.

3:27

S… Speaker 1 (9- Generic Methods)

So the max is 3.

3:29

S… Speaker 2 (9- Generic Methods)

Now we can also pass two user objects,

3:32

S… Speaker 2 (9- Generic Methods)

so let's say one user with 10 points and another

3:37

S… Speaker 2 (9- Generic Methods)

user with 20 points.

3:39

S… Speaker 2 (9- Generic Methods)

Obviously the return type of this method is now going to be a user object.

3:43

S… Speaker 2 (9- Generic Methods)

So let me print it

3:47

S… Speaker 2 (9- Generic Methods)

we get this long string which includes the fully qualified name of the class

3:52

S… Speaker 2 (9- Generic Methods)

followed by an add sign and then a hash code.

3:55

S… Speaker 2 (9- Generic Methods)

I talked about this in the previous parts of this series.

3:57

S… Speaker 1 (9- Generic Methods)

So when we pass an object to the print line method,

4:00

S… Speaker 2 (9- Generic Methods)

the tool string method on that object gets called.

4:03

S… Speaker 2 (9- Generic Methods)

So that long string that you saw returns from the default implementation

4:07

S… Speaker 2 (9- Generic Methods)

of the tool string method.

4:08

S… Speaker 2 (9- Generic Methods)

To solve this problem,

4:10

S… Speaker 2 (9- Generic Methods)

we go back to the user class and overwrite the tool string method.

4:14

S… Speaker 2 (9- Generic Methods)

So first we apply

4:16

S… Speaker 2 (9- Generic Methods)

the overwrite annotation.

4:18

S… Speaker 2 (9- Generic Methods)

We're telling the Java compiler that we're overwriting one of the methods inherited

4:23

S… Speaker 2 (9- Generic Methods)

from the base class.

4:24

S… Speaker 2 (9- Generic Methods)

And then we type public string to string.

4:28

S… Speaker 1 (9- Generic Methods)

And here we can return a simple string

4:32

S… Speaker 1 (9- Generic Methods)

like this.

4:33

S… Speaker 2 (9- Generic Methods)

Points equals plus points.

4:36

S… Speaker 1 (9- Generic Methods)

Now,

4:37

S… Speaker 1 (9- Generic Methods)

let's run a program so you can see that the user

4:42

S… Speaker 2 (9- Generic Methods)

with 20 points is the maximum of these two user objects.

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