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Let's not look at two dimensional art Gutierrez what we saw in the previous lesson we're one dimensional

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art is a one dimensional array can be visualized as a sequence of elements laid out along a line in

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a tree you can visualize elements to be laid out in a great form like in The Matrix.

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In fact mattresses are usually implemented using tree areas.

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It's also possible to how arrays of higher dimensions but they are very rare in practice.

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So let's just go ahead and see how UDRS are created integrated elements are arranged in rows and columns

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.

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Here is a two dimensional array that has four rows and columns and has a total of eight elements like

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a one dimensional array.

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It is also an object in Java and it can start with primitives an object references index numbering for

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both rows and columns beginning with zero.

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Now if this arrays named as my array then my array at indexes 0 and 1 will get it and the element from

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0 throw unfussy column which has a value of 11.

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So with this can be implemented using such dreariest.

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Similarly for the common student example unconsidered would students on their assignments scores in

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a particular course.

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Then we can store that information in a query each that can correspond with a student and the values

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stored in each row can be the assignment of course like in the case of one dimensional arrays.

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There are three ways to create gutiérrez And they're also created using similar syntax.

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Let's look at how we can create Overmeyer example.

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And here's a fast way to do it similar to one dimensional arrays.

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We use the word new in one dimensional array.

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We had only one pair of square brackets on either side of the assignment.

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Since we know how two dimensions we will have two pairs so square brackets on either side of the assignment

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on the right hand side.

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The number of rows is indicated in the first square brackets while the number of columns is indicated

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in the second square brackets.

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The square brackets on the left hand side will be empty.

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Let's see how JVM internally implements this to the three Gibeon basically creates a one dimensional

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array with four elements corresponding to the four rows.

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And these four elements do not contain the raw data but each of the elements is actually an object reference

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reference to another and array with two elements.

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And these are referenced in arrays represent actual rows and they contain the actual data as a byte

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for the arrays and all of the internal arrays are initialized with default 0.

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You can also see the two dimensional index numbers associated with each element.

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So you can see that it is actually implemented as a one be array under elements or simply object references

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which are done differencing one dimensional address this fact can be observed in the declaration itself

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.

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So let's review the declaration once again.

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We know that an articulation includes a type followed by square brackets which is then followed by the

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Iranian and we can read it as an army of bike.

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Now if the pipe is and we can read it as an army off and on we know it is a one dimensional array.

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Now the pipe itself is trade off and then we can read it as an arc of RF and or in other words on off

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and of it.

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So although it doesn't set the machinery in reality it is actually one dimensionality.

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No not my example elements where any dealings with default value.

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So we need to initialize them explicitly.

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And that can be done as shown here.

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And this is an illustration of how the RL looks after element initialization.

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Here is the second way to create a query in one be array.

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We only had commas operator values but we know that a 2D array is an array of some type.

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So we have one array and within that array we have nested arrays with each an asterisk corresponding

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to zero and for each history we will have a pair of nested braces on the actual DWB side in that nested

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braces.

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Finally as in the case of one dimensional arrays we have this simplest notation.

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Now here we have something interesting in our Meyera example.

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We saw that there were four rows on all of the rows were sorting the same number of elements.

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That is two elements.

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So each will have two elements but due to the bit Djala implements.

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Or is it also possible for different rows in a truly array to have different number of elements.

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So let's see how that's possible.

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And also where it can be useful.

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So here we created €2 with duros but we don't specify any value for the number of columns.

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Next we cleared the first row which would have five elements or five columns Mexicans would be created

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with two elements.

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So as you can see the column size is not fixed.

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Kruskal now has five columns.

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When the second row has only two columns one example use of this kind of recreation is a symmetric marker

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X with the number of rows is equal to the number of columns and elements about the diagonal which are

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shown in red here are simply duplicate of elements below that I acknowledged which are shown in blue

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.

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So by creating an array with irregular row sizes begin to watch dooring that duplicate in red.

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And so the symmetric matrix will now be a triangular matrix as shown here.

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Each row will be represented by an array of different.

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In this example frontrow would be an array of length one.

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Well secondo would be an array of Lendu and so on.

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So that's a pretty cool way to save some storage space and it would be very useful for very large mattresses

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like in the case of one dimensional array.

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Lenth field can also be used on it.

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However since internally the array is implemented as a one dimensional array accessing lenth from the

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ARI would return the number of rows in our miring example which are four rows on two columns land would

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read for accessing left on the first element of my arm would return to this example shows how we can

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make a reference to one of the rows which is a suburb.

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So he had a variable called row which is an array is assigned the third row.

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Since index numbering begins with zero.

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And that's the end of our discussion on the arrays.

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Probiotics are sometimes very useful but are much less commonly used than one dimensional allergies

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later in the first version of our project.

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We will use two areas similar to the way we extended the syntax from one to two dimensions.

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We can further extend to higher dimensions dimensions higher than two dimensions are pretty rare in

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practice