Wrapper Classes in Java: Definition & Example

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  • 0:04 Primitive Data Type &…
  • 2:11 Methods and Examples
  • 3:55 Lesson Summary
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Lesson Transcript
Instructor: Martin Gibbs

Martin has 16 years experience in Human Resources Information Systems and has a PhD in Information Technology Management. He is an adjunct professor of computer science and computer programming.

A wrapper is like a blanket over another Java data type, such as the primitive data types int, char, float, and double. This lesson will define the term and provide working code examples.

Primitive Data Type & Wrapper Class

Java provides several primitive data types. These include int (integer values), char (character), double (doubles/decimal values), and byte (single-byte values). Sometimes the primitive data type isn't enough and we may actually have to work with an integer object.

Let's first look at the wrapper classes. First, we'll list the Java primitive data type and then we'll explain its wrapper class.

Java Primitive Data Type Wrapper Class
int Integer
double Double
boolean Boolean
byte Byte
char Character
float Float
long Long
short Short

Notice that all wrapper classes start with a capital letter, such as Integer, while the primitive data types are lowercase, such as int.

Now let's look at basic syntax. There are a couple of ways to use the wrapper classes. The first is to simply declare them with the upper-case wrapper name, like what you're seeing below:

Java wrapper basic

This is perfectly valid, but it could be a little confusing because many of the wrapper classes share the name of the primitive data type. If you use a mix of primitive data types and wrapper classes, the code might be a little harder to maintain.

The other option is to use the wrapper class as you would other classes. That is, when you want to create a new instance of that class, use the new keyword to instantiate, which means to create, an object of that type. Take a look at the code below:

Java wrapper instantiate

In this image, you're seeing a new Integer object declared.

First, we created a primitive integer and gave it a value of 10. Next, we instantiated (created) a new instance of the Integer class and gave it the value of the primitive variable.

Methods and Examples

A really cool feature of the wrapper classes is that they include their own methods that can be used with each wrapper class. For example, you can show the double value of an integer variable, compare values, or even convert values to a string.

Let's look at a code example for the heavy hitter Integer.

Int Primitive = Integer Wrapper

The wrapper class for the int data type is the Integer class. Let's expand upon the previous example of the Integer and use one of the methods to convert it to a Double. The method to do this is doubleValue(), and the code looks like:

Java wrapper integer method

Now that we've created a new instance of Integer, let's look at some of the methods that come with these powerful tools in the Java toolbox.

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