Package: java.util
public class Arrays extends Object
✅ Important:
- Arrays is a utility class
- All methods are static
- Used for sorting, searching, comparing, copying, filling, and converting arrays
1️⃣ Sorting Methods (Most Used)
static void sort(array)
Use: Sorts array in ascending order
int[] nums = {5, 3, 8, 1};
Arrays.sort(nums);
System.out.println(Arrays.toString(nums)); // [1, 3, 5, 8]
static void sort(array, fromIndex, toIndex)
Use: Sort part of array
Arrays.sort(nums, 1, 3); // sorts index 1 to 2
static void parallelSort(array)
Use: Faster sorting for large arrays (multi‑threaded)
2️⃣ Searching Methods
static int binarySearch(array, key)
Use: Searches element using binary search
✅ Array must be sorted first
int index = Arrays.binarySearch(nums, 5); System.out.println(index); // index of 5
static int binarySearch(array, fromIndex, toIndex, key)
Use: Search within a range
3️⃣ Comparison Methods
static boolean equals(array1, array2)
Use: Compare 1‑D arrays
int[] a = {1,2,3};
int[] b = {1,2,3};
System.out.println(Arrays.equals(a, b)); // true
static boolean deepEquals(array1, array2)
Use: Compare multi‑dimensional arrays
int[][] x = {{1,2},{3,4}};
int[][] y = {{1,2},{3,4}};
System.out.println(Arrays.deepEquals(x, y)); // true
static int compare(array1, array2)
Use: Lexicographical comparison
static int mismatch(array1, array2)
Use: Returns first index where arrays differ
int idx = Arrays.mismatch(new int[]{1,2,3}, new int[]{1,9,3});
System.out.println(idx); // 1
4️⃣ Filling Methods
static void fill(array, value)
Use: Initialize array with same value
int[] arr = new int[5]; Arrays.fill(arr, 10);
static void fill(array, fromIndex, toIndex, value)
Use: Partial fill
5️⃣ Copying Methods
static array copyOf(original, newLength)
Use: Resize or clone array
int[] copy = Arrays.copyOf(arr, 3);
static array copyOfRange(original, from, to)
Use: Extract portion of array
int[] sub = Arrays.copyOfRange(arr, 1, 4);
6️⃣ Conversion Methods
static String toString(array)
Use: Convert array to readable string
System.out.println(Arrays.deepToString(x));
static String deepToString(array)
Use: Multi‑dimensional arrays
System.out.println(Arrays.deepToString(x));
static List asList(T… a)
Use: Convert array to fixed‑size list
⚠️ Note: With primitive arrays, it returns a single element list (array reference).
String[] names = {"A","B","C"};
List<String> list = Arrays.asList(names);
7️⃣ Stream & Utility Methods (Java 8+)
static IntStream stream(int[] array)
Use: Functional operations
int sum = Arrays.stream(nums).sum();
static void setAll(array, generator)
Use: Populate array dynamically
✅ MOST COMMONLY USED Arrays METHODS (Interview + Projects)
🔥 Used very frequently
sort()
binarySearch()
equals()
toString()
fill()
copyOf()
copyOfRange()
🔶 Used in advanced scenarios
deepEquals()
deepToString()
parallelSort()
mismatch()
stream()
