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Every primitive type has a wrapper class.

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Java is object oriented, that means there is a class for every primitive type.

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In this lesson, you'll learn about wrapper classes.

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You can find the code for this lesson by following this path in the resources.

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Let's get one question out of the way, what is a rapper?

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A rapper is an immutable class that wraps around a primitive type.

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Here's an example, integer integer is an immutable class that wraps around the type because integer

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is an immutable class, then variables of that type story, a reference to an object.

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They can be now, they can call methods, but they cannot change, which means they are immune to the

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reference trap.

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So inside Rupert Java, there are a bunch of primitive variables if you view the runtime.

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You'll notice that a primitive is just a value and nothing more, and because it's primitive, the variable

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cannot be null and it cannot call any methods.

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And so we can set up a variable of type integer.

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Equal to a new object of the integer class and then pass the integer value into the constructor.

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And now the variable stores a reference to an integer object, the integer object contains a field that

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matches the value we pastan.

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And because it's an object, the variable can call many methods like.

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Percent to string int value, double value and so much more.

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And because it's an object, it can also be No.

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But there's a shorter way to define a proper object.

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The syntax where you directly create a new object of the integer class with the value inside the constructor

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is deprecated.

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You can just assign the value directly in Java is going to create an object and update the field behind

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the scenes.

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You can confirm this by running the debugger.

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And like before, the variable stores, a reference to an integer object and the integer object contains

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a field that matches the value of Pastan.

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And here are some more upper classes, double long and character like integer, they are immutable class

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types, variables of each type story reference to an object they can be know they can call methods they

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cannot change.

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You cannot update the status of an immutable object, which means they're immune to the reference trap.

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So inside, Rupert Jarvis said the three variables equal to a new object of the respective wrapper class,

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first, we're going to do with the Longway.

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All the rerun, the debugger.

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Step through each line.

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And notice that every object contains a field that matches the value that we bastin because they're

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all objects, each one can be null and can call methods.

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And so in general, the syntax where you create a new object of the wrapper class is deprecated, you

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can just assign the value directly and Jeff is going to create an object and update every field behind

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the scenes.

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Let's talk about the reference trap rappers are immutable class types, so they are immune to the trap.

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A rapper such as Integer doesn't have any suitors, so it's impossible to update the field.

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Let's set another integer variable equal to the first.

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Launched the debugger, and it follows that when you set an integer variable equal to another, it copies

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of the reference inside and now both variables are going to point to the same integer object.

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Should I worry about the reference trap?

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No, it's impossible to update the state of the object when you assign the variable annuity Energia.

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When you assign the variable a new integer, it's going to equal a brand new object of the integer class

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with the value 10, the same applies to the other rappers.

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OK, so you might be asking one to use primitive one to use proper use, primitive 90 percent of the

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time, primitive takes up less space and they're faster, only use a wrapper when you need the variable

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to be null or when you need to call a method from the variable.

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In this lesson, you learned about wrapper classes.

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A wrapper class wraps around a primitive type javas object oriented, so there's a class for every primitive

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type.

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Use a primitive type 90 percent of the time, because they take up less space and they're faster, only

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use a wrapper when you absolutely need to, when you need the variable to be known or if you need to

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call a method from the variable.