Question 31

Explanation

UKOCP20750:

Let's check all the options one by one:

Flyable flyable = new Flyable();

✗ Can't instantiate an interface.

Flyable flyable = new Flyable(){};

✗ fly() method has not been implemented.

Flyable flyable = new Flyable() {
    public void fly() {
        System.out.println("Flying high");
    }
}

✗ semicolon is missing at the end

Flyable flyable = new Flyable() {
    public void fly() {
        System.out.println("Flying high");
    }
};

✓ Correct syntax, fly() method has been implemented successfully.

var flyable = new Flyable() {
    @Override
    public void fly() {
        System.out.println("Flying high");
    }
    
    public void stop() {
        System.out.println("Stopping");
    }
};
flyable.fly();
flyable.stop();

✓ Local variable Type inference was added in JDK 10.

Reserved type name var is allowed in JDK 10 onwards for local variable declarations with initializers, enhanced for-loop indexes, and index variables declared in traditional for loops. For example,

var x = "Java"; //x infers to String

var m = 10; //m infers to int

The identifier var is not a keyword, hence var can still be used as variable name, method name or package name but it cannot be used as a class or interface name.

Variable 'flyable' infers to anonymous inner class implementing Flyable interface. The anonymous inner class correctly overrides fly() method and provides a new stop() method. Both these methods can be invoked on reference variable 'flyable' as it is of anonymous inner class type.