JAVA ARRAY CHEAT SHEET | QA SDET | TEST AUTOMATION
Java Array Cheat Sheet - Summary Format
1. Array Definition:
Arrays are fixed-size, index-based data structures that store similar types of data.
Example declarations:
int[] a = new int[10];
char[] c = new char[15];
String[] s = new String[20];
2. Array Structure:
Indexing starts at 0. For example: int[] arr = {21, 15, 37, 53, 17}
3. Array Declaration:
Two ways:
int[] arr;
int arr[];
4. Array Initialization:
Step-by-step: arr[0] = 21; arr[1] = 15; ...
With new: int[] arr = new int[]{21, 15, 37, 53, 17};
Directly: int[] arr = {21, 15, 37, 53, 17};
5. Array Traversal:
Using for loop:
for (int i = 0; i arr.length; i++)
System.out.println(arr[i]);
Using enhanced for loop:
for (int i : arr)
System.out.println(i);
6. Multidimensional Arrays:
2D: int[][] arr = {{1,2,3},{4,5,6},{7,8,9}};
3D: int[][][] arr = {{{1,2,3},...}, ...}
Jagged: Arrays of different lengths inside a 2D array
7. Anonymous Arrays:
Used without a name: new int[]{1, 2, 3, 4, 5};
8. Array to List Conversion:
List String list = Arrays.asList("One", "Two", "Three");
9. Array to Stream:
IntStream stream = Arrays.stream(new int[]{1, 2, 3});
10. Array Length:
Use arr.length to get size
11. java.util.Arrays Methods:
sort() - Sort array
stream() - Convert to stream
spliterator() - Get spliterator
setAll() - Initialize all elements
fill() - Fill with a value
copyOf() - Copy array
asList() - Convert to list
binarySearch() - Search value
12. Pros:
Easy to implement
Supports primitives and references
Fast data retrieval
13. Cons:
Fixed size
Not type safe
No built-in methods