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You need to learn the difference between a raise an array lists.

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Both can store many values at the same time, there is one difference, arrays are fixed, array lists

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are sizable.

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So far you've used arrays and in this lesson you're learned to use array lists.

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We can start setting up by following this path and the resources and open up the folder array lists.

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Kate, now an array is fixed in size, once you define the size of an array, you cannot change it.

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The number of elements is fixed.

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So inside the class you'll notice a group with three names and Katie just joined the group.

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So you need to add her name as well.

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But you cannot resize an array, so you need to set another variable equal to a brand new array of four

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elements.

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String new group is equal to a new string array that can store four elements.

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And then create a for loop that runs through the length of the first three.

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And inside the fur luper and up to each element in the new era, equal to values from the old one.

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And now finally, you can add Katie to the group.

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Well, that was so much work just by visualizing the runtime, which I'm going to do right now.

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You'll see that it's really crazy how much work needs to go into first, updating every element from

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the old array.

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And then only then can we add Katie to the group to add one element, we had to make a brand new array

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and start over.

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This is not efficient.

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And that is why we have the array list, the array list is sizable.

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The Israelis can add or remove elements at will, and it can only store objects, it cannot store primitives.

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So I hope you can now realize why we did the lesson on wrapper classes.

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To create an array list, you need to write the class type array lists, write what it can store inside

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of a generic, and generics can only accept class types.

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Generics cannot accept primitive types, i.e., if you want to have an array, a list of whole numbers,

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you would write array list integer, not array list int.

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And the third step is to make space for a new object of the area list class.

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Inside sizable arrays that Java Right array list autocomplete import the areolas class, this array

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list is going to store string objects, I'm going to call it names will set names equal to a new object

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of the Israelis class that can store elements of type string.

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Now, remember, the list is an object, so it has many methods that can add or remove elements.

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So we're going to use the ADD method to add three names.

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Joe.

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Jim and John.

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And now you can loop through each element in the array lists, we can use Intellisense to complete a

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loop and here we'll make sure the loop runs through the size of the aerialists.

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The size of an array list returns the number of elements.

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It's equivalent to the length of an array.

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Some generic names that size and let's have a look.

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As expected, the size is three, and so the loop is going to start from equal to zero until it reaches

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the last index and inside the loop, we need to get the element that each index.

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But how do you access values from an object?

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I hope you guessed it a getter.

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The aerialists class defines a getter.

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Get the returns and Alimentarius for an index.

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Since the terrorist public, we can call it from any array list object using DOT syntax, so inside

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the loop, the names array list can get for every element at the index I.

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And we'll print the result.

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Launching the debugger.

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The getter returns every element at the requested index.

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OK, and now let's just say Joe decided to change his name to Joe Fresh, hmmm, how do you update your

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values in an object?

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I hope you guessed it a Seder.

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The Israelis class defines a Seder set that updates an element that a certain index.

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And so, as you can see, it expects to parameters the index and the elements.

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And since the ceteris public, we can call it from any object of the Israelis class.

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So I'm going to set the element at Index zero to Joe Fresh.

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And that's perfect to the setar update's the value, isn't it awesome?

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Java classes also use the big three steps the area.

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This class has constructor's from which we can create a list of objects.

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The area this class defines a getter.

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And since the letter is public, every aerialists object can call it using dot syntax and the Israelis

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defines a setar once again.

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Since the sitarist public, every aerialists object can call it using DOT syntax.

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In the aerialist class also defines other methods like add and remove, the first method adds an element,

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Alacer, an index, and the second method removes an element, Alacer, an index.

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And since these are public, we can call them from any object of the Israelis class.

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So I'm going to add an element at index three of the names object.

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Katie.

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And as expected, it adds an element that index three.

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We can also remove elements in this case, I'm going to remove the element and index to.

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And unsurprisingly, it removes the element of the next to.

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You know, the Aranesp class also defines a method that clears every element.

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And since the method is public, we can call it so I'm going to call it from the names object.

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And it clears every element.

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If you don't expect the size to change userspace.

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User Ray lists when the number of elements can vary, if you need to add or remove elements, then it's

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a thousand times easier to use an array list.

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And this lesson you learn, the difference between a raise, an array lists, arrays are fixed.

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Whereas array lists are sizable.

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If you don't expect the size to change, use a race, if you expect the size to change user realist's.