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Lesson 22 - Boxing, wrapper classes, packages and more

In the previous lesson, The equals() and clone() methods in Java, we went over the equals() and clone() object methods. Welcome you all to the last tutorial of the basics of the object-oriented programming in Java. We'll finish the remaining pieces of the theory and then we'll meet again in the form applications course.

Boxing, unboxing, and nullable types

We already know the differences between primitive and reference types. Sometimes, it's useful to work with primitive types as we would with reference types. In these cases, we use boxing. We box a primitive type into the general ancestor of all objects - the Object type. Boxing in action would look something like this:

int a = 10;
Object boxedInt = a;

Then, we would be able to work with the variable boxedInt as with a reference type, e.g. to store it into some collection for generic types only. Alternatively, it could contain the null value. An ordinary int would be just copied without any dependencies.

Similarly, we can unbox variables. To do so, all you have to do is


 

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In the final lesson, we'll learn about boxing and unboxing, wrapper classes for Java primitive types, packages, nested classes and more.

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