instanceof-pattern-matching.md

InstanceOf Pattern Matching

Assume we have the following classes.

class Animal{
}

class Cat extends Animal{

    public String name() {
        return "Ketty";
    }
    
    @Override
    public String toString() {
        return "Cat{" + '}';
    }

}

class Dog extends Animal{
    
    public String name() {
        return "Kael";
    }

    @Override
    public String toString() {
        return "Dog{" + '}';
    }  
}

When creating a Cat like this.

Animal animal = new Cat();

And we want to check if it is a Cat, in the previous Java, we could have to code like this.

if(animal instanceof Cat){
    Cat cat = (Cat) cat;
    System.out.println("it is a cat:" + cat.name());
}

Here we used a line of codes to cast the animal instance to Cat type .

In Java 14, it simply becomes:

if(animal instanceof Cat cat){
	System.out.println("it is a cat:" + cat.name());
}