The Arrays utility class

Sort, search, fill, compare, and print arrays with java.util.Arrays.

java.util.Arrays

The java.util.Arrays class provides static utility methods for common array operations. Import it with import java.util.Arrays;.

int[] nums = {5, 3, 8, 1};

Arrays.sort(nums);                      // sorts in place → [1, 3, 5, 8]
int idx = Arrays.binarySearch(nums, 5); // 2 — array MUST be sorted first

int[] copy = new int[5];
Arrays.fill(copy, 7);                   // [7, 7, 7, 7, 7]

int[] a = {1, 2, 3};
int[] b = {1, 2, 3};
Arrays.equals(a, b);                    // true — element-by-element

System.out.println(Arrays.toString(nums)); // "[1, 3, 5, 8]"

Why you can't just print an array directly:

System.out.println(nums);  // [I@5f4da5c3 — useless

Arrays don't override toString(), so printing one gives a type prefix plus a memory hash. Always wrap in Arrays.toString() for a readable one-line view, or Arrays.deepToString() for 2D arrays.

binarySearch answers against the sorted row. Run it on the top row and it still returns an index — just the wrong one, with no exception to warn you.