One-dimensional arrays in Java - Step-by-Step Execution

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Concept Flow - One-dimensional arrays

Declare array variable

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Allocate memory for array

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Initialize elements

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Access elements by index

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Use elements in operations

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End or reuse array

This flow shows how a one-dimensional array is declared, created, filled with values, accessed by index, and used.

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Execution Sample

Java

int[] numbers = new int[3];
numbers[0] = 10;
numbers[1] = 20;
numbers[2] = 30;
System.out.println(numbers[1]);

This code creates an array of 3 integers, assigns values, and prints the second element.

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Execution Table

Step	Action	Array State	Index Accessed	Output
1	Declare array variable 'numbers'	null (no array yet)	N/A	N/A
2	Allocate array of size 3	[0, 0, 0]	N/A	N/A
3	Assign numbers[0] = 10	[10, 0, 0]	0	N/A
4	Assign numbers[1] = 20	[10, 20, 0]	1	N/A
5	Assign numbers[2] = 30	[10, 20, 30]	2	N/A
6	Print numbers[1]	[10, 20, 30]	1	20
7	End of program	[10, 20, 30]	N/A	N/A

💡 Program ends after printing the value at index 1.

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Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5	Final
numbers	null	[0, 0, 0]	[10, 0, 0]	[10, 20, 0]	[10, 20, 30]	[10, 20, 30]

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Key Moments - 3 Insights

▶Why does the array start with zeros after allocation?

▶What happens if I try to access an index outside the array size?

▶Why do we use numbers[1] to get the second element?

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Visual Quiz - 3 Questions

Look at the execution_table, what is the array state after step 4?

A [10, 20, 0]

B [0, 20, 0]

C [10, 0, 0]

D [10, 20, 30]

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Concept Snapshot

One-dimensional arrays in Java:
- Declare: int[] arr;
- Create: arr = new int[size];
- Indexing starts at 0
- Default int values are 0
- Access with arr[index]
- Out-of-bounds causes error

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Full Transcript

This visual trace shows how a one-dimensional array is declared, created with size 3, initialized with values 10, 20, 30 at indexes 0,1,2 respectively, and how accessing numbers[1] prints 20. The array starts with zeros after allocation. Indexing starts at zero, so numbers[1] is the second element. Accessing outside the array size causes an error.