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Wrappers with null

Unlike primitives, a wrapper variable can be uninitialized and has a value of null. A primitive variable that is not initialized is automatically set to its default value (0 in the case of ints). Since wrappers can have null values, this allows us to test if it has been set before using it (unlike primitives). In this exercise, we see the difference in uninitialized primitives and wrapper objects.

Este ejercicio forma parte del curso

Data Types and Exceptions in Java

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Instrucciones del ejercicio

  • Declare a variable of type int called x but do not set its value.
  • Declare a variable of type Integer called y but do not set its value.
  • Display (print) the value of x even though you did not initialize its value.
  • Test if y is null.

Ejercicio interactivo práctico

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public class NullWithWrappers {

	// Declare a primitive integer called x
	static ____ ____;
	// Declare a wrapper Integer called y
	static ____ ____;

	public static void main(String[] args) {
       	// Display x value
		____.____.____(____);
		System.out.println(y);

		// Check if y has been initialized and is null
		if (____ ____ ____) {
			System.out.println("y is not initialized so take corrective steps here");
		}
	}
}
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