Arrays in Java

public class Arrays {
    public static void main(String[] args) {
        // Declaration + initialization
        int[] marks = {85, 90, 78, 92, 88};
        String[] cities = {"Pune", "Mumbai", "Nagpur"};

        // Declaration + later initialization
        double[] prices = new double[5];  // 5 doubles, default 0.0
        prices[0] = 99.99;
        prices[1] = 149.50;

        // Access
        System.out.println(marks[0]);     // 85
        System.out.println(marks.length); // 5

        // for loop — with index
        int sum = 0;
        for (int i = 0; i < marks.length; i++) {
            sum += marks[i];
        }
        System.out.printf("Average: %.2f%n", (double) sum / marks.length);

        // for-each — cleaner
        for (int m : marks) {
            System.out.print(m + " ");
        }
    }
}

// 2D array — matrix
int[][] matrix = {
    {1, 2, 3},
    {4, 5, 6},
    {7, 8, 9}
};

// Print matrix
for (int i = 0; i < matrix.length; i++) {        // rows
    for (int j = 0; j < matrix[i].length; j++) { // columns
        System.out.printf("%3d", matrix[i][j]);
    }
    System.out.println();
}
// Output:
//   1  2  3
//   4  5  6
//   7  8  9

// Student marks — 3 students, 4 subjects
int[][] studentMarks = new int[3][4];
studentMarks[0][0] = 85;   // student 0, subject 0

import java.util.Arrays;

int[] nums = {5, 2, 8, 1, 9, 3};

// Sort
Arrays.sort(nums);
System.out.println(Arrays.toString(nums));  // [1, 2, 3, 5, 8, 9]

// Binary Search (sorted array वर)
int idx = Arrays.binarySearch(nums, 5);
System.out.println("5 found at index: " + idx);  // 3

// Fill
int[] filled = new int[5];
Arrays.fill(filled, 7);
System.out.println(Arrays.toString(filled));  // [7, 7, 7, 7, 7]

// Copy
int[] copy = Arrays.copyOf(nums, 4);  // first 4 elements
System.out.println(Arrays.toString(copy));  // [1, 2, 3, 5]