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Objects can be immutable or immutable.

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In the past, we separated primitive types from class types.

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We can also separate class types into two categories, immutable and immutable.

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In this lesson, you're to learn to tell the difference between mutable and immutable objects.

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To access this lesson, follow this path and your resources and open up the mutable folder.

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Now, another name for Setar is Mutator before we continue to take some time to absorb this sentence.

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Immutable object is an object whose field values can change.

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Immutable object uses Mutator is Setas to update its fields.

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And so inside Maine, the first line creates an object of the car class.

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Let me ask you this, is car a mutable or an immutable class type?

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Take a couple of seconds to think about it.

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The answer is mutable after you create a car object, it's possible to update it.

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In other words, the mutable object can use its mutator as its setas to update its fields.

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And so to keep things simple at its core, what makes an object immutable after creating the object,

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Wicken updated state, that's it.

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We can mutate it.

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Now, what is an immovable object, an immutable object is an object whose field values cannot change,

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an immutable object does not have Mutator doesn't have Setas.

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And you can access this part of the lesson by following this path and the resources and open up the

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immutable folder.

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Can I go inside, Main Espersen, immutable or an immutable class type?

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Think about it.

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The answer is immutable after you create a personal object, it's impossible to update it.

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All of the fields are private and the person class doesn't have any setas.

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This makes every object of the person class immutable.

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It's impossible to update the state of a person object after you create it.

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This leads us to the reference chart, mutable objects are vulnerable to the reference trap.

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Immutable objects are immune to the reference trap.

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So these two tables don't make any sense.

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The reference job doesn't apply to immutable objects, so the tables need to specify that mutable objects

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are the ones that are prone to the reference trap.

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Let's do just that.

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OK, this feels better.

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You now inside main job, we're going to set another variable equal to the first object.

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And then I'm going to update the object from the second variable.

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Then I'll print the gold from both objects.

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Run the code.

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And unsurprisingly, updating the state of the second variable affects the first one.

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When you set a variable equal to another, it copies the value inside in this case, what's inside is

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a reference, and now both variables share a reference that points to the same object.

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If I update the object there, one variable, it's going to affect the other.

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And so mutable objects are vulnerable to the reference trap.

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What about immutable objects?

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Inside Main Java set another variable equal to the first person object.

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OK, what now?

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Every object of the person class is immutable, the fields are private and the person class doesn't

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have any setas.

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So even if both variables share a reference to the same object, there's nothing you can do to update

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the state of either one.

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Let me just put breakpoints.

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You can visualize the runtime.

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And so here, both variables share a reference to the same object, but that doesn't matter because

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we can't update either one.

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All you can do is set the second variable equal to a brand new object.

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But in that case, the second variable story is a new reference that points to a unique object.

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And so I hope you can see that immutable objects are immune to the reference trap.

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OK, so first we need to update this table, because we can also divide class types into two categories,

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mutable and immutable.

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Mutable objects can update their status, immutable objects cannot mutable objects are vulnerable to

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the reference Tropp immutable objects are immune.

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Array is a mutable object, there is a class for every array type.

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There's a class for array of integers, array of double array of long, etc..

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So looking at this example, the variable equals the new object of the entire class.

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The variable stores a reference to an object, the variable can be no, it can call methods, you can

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update the state of an array, and arrays are vulnerable to the reference trap.

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And since arrays are mutable objects, we don't need these two tables, the Redundance.

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Remove them.

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And this looks a lot better.

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Let's recap, you learn to tell the difference between mutable and immutable objects.

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You can update the state of immutable object, but you can't update the state of an immutable object.