Implement zero mover algorithm to shift all zeros to the end of array

Java/zeroInTheEnd.java

@@ -0,0 +1,57 @@
+import java.util.*;
+
+public class zeroInTheEnd {
+
+	/**
+	 * Move all zeros in the array to the end while preserving the order
+	 * of non-zero elements. This runs in O(n) time and O(1) extra space
+	 * (modifies the array in-place).
+	 */
+	public static void moveZerosToEnd(int[] a) {
+		int n = a.length;
+		int write = 0; // position to write the next non-zero
+		for (int read = 0; read < n; read++) {
+			if (a[read] != 0) {
+				a[write++] = a[read];
+			}
+		}
+		// fill remaining positions with zeros
+		while (write < n) {
+			a[write++] = 0;
+		}
+	}
+
+	public static void main(String[] args) {
+		Scanner sc = new Scanner(System.in);
+		try {
+			if (!sc.hasNextInt()) {
+				// Demo fallback
+				int[] demo = {0, 1, 0, 3, 12, 0, 5};
+				System.out.println("No input detected — running demo: " + Arrays.toString(demo));
+				moveZerosToEnd(demo);
+				System.out.println(Arrays.toString(demo));
+				return;
+			}
+
+			int n = sc.nextInt();
+			int[] a = new int[n];
+			for (int i = 0; i < n; i++) {
+				if (!sc.hasNextInt()) {
+					System.err.println("Expected " + n + " integers but got fewer.");
+					return;
+				}
+				a[i] = sc.nextInt();
+			}
+
+			moveZerosToEnd(a);
+
+			// print result as space-separated values
+			StringJoiner sj = new StringJoiner(" ");
+			for (int v : a) sj.add(String.valueOf(v));
+			System.out.println(sj.toString());
+		} finally {
+			sc.close();
+		}
+	}
+
+}