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We just saw how we can group
together different objects

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by using an array with
a common base class.

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Now let's see how to use a cast so
we can call makeSound on our dog object.

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First, since we got rid of our dog
variable, let's make a new one.

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Let's add a new line after our
object array and type dog.

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And we'll name it dog, and set it
equal to the first item in our array.

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So list at position 0, which gives
us an incompatible types error.

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This is where the cast comes in.

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A cast, or type casting,
is when you tell Java that an object

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is a more specific
descendant of that object.

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Essentially moving the object
up its family tree.

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For example, if we were storing
a car as a vehicle object and

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needed to turn it back to a car object,
we would use a cast.

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To use a cast, you just write the name
of the class between parentheses.

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So right after the equal sign,

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let's add a cast to change
list 0 to a dog object.

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So parenthesis and
inside them we write the class, Dog.

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Nice, it doesn't look
like we have any errors.

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And if we run it, We get the right output.

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But before we move on,

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let's see what happens if we
try to merge these two lines.

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Let's hide the run panel,
and then delete line seven,

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and change dog to list at position zero.

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Then let's add the cast,
and it doesn't work.

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It turns out that the call to
makeSound happens before the cast.

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So to make sure that
the cast happens first,

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we just need to use some parentheses.

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Okay, we've got an array of objects and

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seen how we can use casts to move
an object up its family tree.

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But this only works because we know
exactly where our dog is in the array.

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If we accidentally tried to cast
our dog food object to a dog,

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we'd crash the program.

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And just to make sure, Yep,
we get a class cast exception.

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Cmd or Ctrl+Z to undo, and
we're back to working code.

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So instead of just picking
out the dog object,

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let's loop through our list array and
only call makeSound if the object

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actually has a makeSound method,
meaning the object is an animal.

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Let's delete line 7 again, and let's use
a for each loop to loop through our array.

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For object, we'll call it object, and,

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which is represented by a colon,

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our list array, and add the brackets.

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And inside the for loop, we need to
determine if this object is an animal.

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Luckily, there's a keyword for this.

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Let's write an if statement.

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And for the condition,
let's check that object, instance of.

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Animal.

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And notice that instanceof is
all one word and all lowercase.

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Using the instanceof operator
allows us to check if one object

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is an instance of another.

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So inside the if statement,

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after we add our brackets,
object is guaranteed to be an animal.

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However, even though it's guaranteed to be
an animal, we'll still need to cast it.

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Let's type object., and choose makeSound

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to have IntelliJ automatically
add the cast and call the method.

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Awesome, now let's run the app.

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And perfect,
we're still getting the same output.

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Using casts and the instance of operator

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gives us a lot more freedom
with how we handle our objects.

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Why don't you get a little more practice,
and

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in the next video, we'll take
a deeper look at the object class.