Assume x is an integer and an array is declared as follows....

Assume x is an integer and an array is declared as follows. Which of the following statements correctly assigns the value 100 to each of the array elements? int [] nums $=$ new int [4]; a. $\operatorname{for}(\mathrm{x}=0 ; \mathrm{x}<3 ;++\mathrm{x})$ nums $[\mathrm{x}]=100$; b. $\operatorname{for}(x=0 ; x<4 ;++x)$ $\operatorname{nums}[\mathrm{x}]=100$; c. for $(\mathrm{x}=1 ; \mathrm{x}<4 ;++\mathrm{x})$ nums $[\mathrm{x}]=100$; d. $\operatorname{for}(x=1 ; x<5 ;++x)$ nums $[\mathrm{x}]=100$;

Assume x is an integer and an array is declared as follows. Which of the following statements correctly assigns the value 100 to each of the array elements?
int [] nums $=$ new int [4];
a. $\operatorname{for}(\mathrm{x}=0 ; \mathrm{x}<3 ;++\mathrm{x})$
nums $[\mathrm{x}]=100$;
b. $\operatorname{for}(x=0 ; x<4 ;++x)$
$\operatorname{nums}[\mathrm{x}]=100$;
c. for $(\mathrm{x}=1 ; \mathrm{x}<4 ;++\mathrm{x})$ nums $[\mathrm{x}]=100$;
d. $\operatorname{for}(x=1 ; x<5 ;++x)$ nums $[\mathrm{x}]=100$;

Key Concepts

Array Indexing

Array indexing refers to accessing the individual elements within an array using indices. In most programming languages, including Java, arrays are zero-indexed, meaning that the first element is accessed with index 0 and the last element is accessed with an index that is one less than the number of elements in the array. Understanding how array indexing works is essential to correctly manipulating arrays and avoiding errors such as accessing indices that are out of bounds.

For Loop Iteration

For loop iteration is a control structure that enables the repeated execution of a block of code with a counter variable. It consists of an initialization, a condition, and an increment or decrement step. When iterating over an array, it is crucial to initialize the loop with the correct starting index, define a condition that does not exceed the array's bounds, and update the counter appropriately so that every array element is processed.

Off-by-One Errors

Off-by-one errors occur when the loop iterates one time too many or one time too few, typically due to incorrect start or end conditions. In the context of array manipulation, these errors can result in either missing an element or trying to access an index that exceeds the bounds of the array, leading to runtime errors. Attention to the proper start index and boundary condition in loops is key to avoiding such errors.

Transcript

00:02 Okay, for this question they ask us to assume we have a two -dimensional right numb and it holds four rows and seven columns.

00:19 Okay, and now they ask what correctly assigns, so assigns third physical column of each row.

00:43 Well, let's see.

00:44 This question they must be getting at making sure we note how arrays are indexed.

00:51 They always start at zero.

00:53 So for rows, you can actually access row zero, you can actually access row one, two, and three.

00:59 You won't be able to access any other rows.

01:05 When they want us to assign the, let's see, close this, when they want us to assign the third column, well, the first column starts at zero.

01:19 So we're going to have code somewhere that will say a number, and then we'll have two to access the third column.

01:28 And all of them seem to have that for a statement.

01:32 Let's see.

01:34 And if they're going to assign to it, they have to have some invalid statement.

01:39 And well, if you look at part a, they don't even have a semicolon.

01:43 So that's the only reason why that one is not valid.

01:47 Now let's see.

01:49 If we're going to assign to the column of each row, the third column, well, you're going to need to do that many times, so we're going to need a four loop.

01:59 We're going to need to include the very first row out of all four of them.

02:02 So we're going to start at zero...

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