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John Sader: Everyone, and welcome to my video on traversing 2D arrays in Java. Let's get started.

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John Sader: So let's look at one dimensional arrays first so you can see I use Java code to declare an instantiate a on d array. And then I sort of made this visualization of what that really looks like. Right? So arrays are 0 based, meaning that their index starts at 0.

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John Sader: So if we look at that the number one box. That's our 0 index. And then our first index is where the 2 is, and our second index is where the 3 is. So how do we traverse a one d array? Well, we're going to use a for loop.

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John Sader: so our for loop. is gonna use I and it's going to increment over the array. meaning that as I, meaning that I points to our index, right? So we're gonna start with I at 0. And then we're gonna have the condition. I is less than array dot length, which is a a property of our integer array

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John Sader: meaning the link. So that's gonna be 3, right? Because we have 3 elements in this array. and then the body, we're just doing a simple print statement. Okay.

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John Sader: so our first iteration. I is going to start at 0.

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John Sader: So when we call a ray at the I index, we're calling array at the 0 index, which is one. Okay? So then, we're incrementing. I so you can see when I equals 0 pointing at one, we increment I for the second iteration through the loop.

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John Sader: I now equals one, which means it's pointing at 2.

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John Sader: Then we go one more and I equals 2. It's pointing at 3 At this point I increments, and I equals 3. that's also our array dot link. So is 3 less than 3. No, it's not so. We're done with the loop. We jump out and move on to the rest of our code.

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John Sader: Okay. So now let's look at a 2D array. so a two-dimensional array basically just means. it's an array of arrays. Okay? So whereas with our one dimensional array, every element was an integer.

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John Sader: Now, every element is an array. Okay? And this specific example, each of those

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John Sader: array elements

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John Sader: have elements, right? Because they're an array. And those elements are integers. Okay? So we see, we have 3 elements in our outer array.

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John Sader: And then within each inner right, we also have 3 elements. So we have 9 total elements. okay.

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John Sader: so

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John Sader: let's break this down going with using a for loop. Okay?

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John Sader: So you'll notice our outer for loop where I equals 0. I is less than a rate out length. I plus that is exactly the same as the one dimensional right? Right? Because

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John Sader: we're doing the same thing. We are

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John Sader: going through each element in the array.

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John Sader: What's different is the body because we have a nested for loop. And the reason we have that is because at each element we need to further

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John Sader: look into it and look at the integers in each element. Right?

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So in our first array we have 1, 2, 3,

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John Sader: so J is going to be used as the like sub index. of the specific element. So J equals 0

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John Sader: and I equals 0. So we're pointing at that one. Okay? And I is gonna stay 0 for the whole time. We're looking at that first element because we're going to execute

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John Sader: the entirety of that second, the nested for loop. before we increment. I

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John Sader: okay, I hope that makes sense. So Jay, Jay starts at 0 right? And this is going to be just like the last example, we're going to increment. J, it equals one. Now, we're pointing at that 2. And then we're going to increment again to 2. Now we're pointing at that 3. Okay.

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John Sader: now, at this point J will equal 3,

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John Sader: and it won't meet that for loop condition. So we're gonna jump out of that for loop. And we're gonna get to the bottom of our outer for loop

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John Sader: where I gets incremented. Okay, so I is going to increment. And then we go back into our

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John Sader: nested for loop. Right? And J is, gonna we're gonna start from 0 again.

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John Sader: So now I equals one and J equals 0. We're pointing at that 4.

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John Sader: And then what's gonna happen? We're gonna increment J and point at that 5. And then we're gonna increment J again and plant that 6. Okay.

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John Sader: get to the end of that. And now we're gonna increment I and J is equal to 0. And then we keep going until we have traversed every single element in this 2D array. At this point. I increments to 3, and we jump out of our for loop.

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John Sader: and we execute the rest of our code. all right, that's it. Thank you.