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Merged
Nullkernel merged 1 commit into from
Apr 5, 2026
+194 −128
Merged

Harden CLI demos against invalid input and validate HashTable size #16

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76 changes: 47 additions & 29 deletions Data-Structures/HashTable.java
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Original file line number Diff line number Diff line change
@@ -1,9 +1,10 @@
import java.util.Scanner;

public class HashTable {
static int size;
static Dataitem[] hasharray;
static final Dataitem DELETED = new Dataitem(-1, -1);
public class HashTable {
static int size;
static Dataitem[] hasharray;
static final Dataitem DELETED = new Dataitem(-1, -1);
private static final String INVALID_INT_MESSAGE = "Invalid input. Please enter an integer.";

static class Dataitem {
int data;
Expand All @@ -15,12 +16,31 @@ static class Dataitem {
}
}

static void initialise() {
Scanner sc = new Scanner(System.in);
System.out.print("Enter the size of the Hash Table: ");
size = sc.nextInt();
hasharray = new Dataitem[size];
}
static void initialise(Scanner sc) {
size = readPositiveInt(sc, "Enter the size of the Hash Table: ");
hasharray = new Dataitem[size];
}

static int readInt(Scanner sc, String prompt) {
while (true) {
System.out.print(prompt);
if (sc.hasNextInt()) {
return sc.nextInt();
}
System.out.println(INVALID_INT_MESSAGE);
sc.next();
}
}

static int readPositiveInt(Scanner sc, String prompt) {
while (true) {
int value = readInt(sc, prompt);
if (value > 0) {
return value;
}
System.out.println("Invalid input. Please enter an integer greater than 0.");
}
}

static int hashcode(int key) {
return Math.floorMod(key, size);
Expand Down Expand Up @@ -69,22 +89,20 @@ static void display() {
}
}

public static void main(String[] args) {
initialise();
Scanner sc = new Scanner(System.in);

System.out.print("Enter the number of Insertions: ");
int n = sc.nextInt();

for (int i = 0; i < n; i++) {
System.out.print("Enter the key: ");
int key = sc.nextInt();
System.out.print("Enter the element: ");
int element = sc.nextInt();
insert(key, element);
}

System.out.println("Insertion done!");
display();
}
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
initialise(sc);

int n = readPositiveInt(sc, "Enter the number of Insertions: ");

for (int i = 0; i < n; i++) {
int key = readInt(sc, "Enter the key: ");
int element = readInt(sc, "Enter the element: ");
insert(key, element);
}

System.out.println("Insertion done!");
display();
sc.close();
}
}
74 changes: 45 additions & 29 deletions Data-Structures/Queue/CircularQueue.java
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Original file line number Diff line number Diff line change
Expand Up @@ -77,15 +77,34 @@ public boolean isFull() {
}
}

public class CircularQueue {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);

System.out.print("Enter Queue size: ");
int capacity = sc.nextInt();

Queue queue = new Queue(capacity);
int choice;
public class CircularQueue {
private static int readInt(Scanner sc, String prompt) {
while (true) {
System.out.print(prompt);
if (sc.hasNextInt()) {
return sc.nextInt();
}
System.out.println("Invalid input. Please enter an integer.");
sc.next();
}
}

private static int readPositiveInt(Scanner sc, String prompt) {
while (true) {
int value = readInt(sc, prompt);
if (value > 0) {
return value;
}
System.out.println("Invalid input. Please enter an integer greater than 0.");
}
}

public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int capacity = readPositiveInt(sc, "Enter Queue size: ");

Queue queue = new Queue(capacity);
int choice;

do {
System.out.println("\n--- Circular Queue Operations ---");
Expand All @@ -94,18 +113,15 @@ public static void main(String[] args) {
System.out.println("3. Peek");
System.out.println("4. Display");
System.out.println("5. Is Full?");
System.out.println("6. Is Empty?");
System.out.println("7. Exit");
System.out.print("Enter your choice: ");

choice = sc.nextInt();

switch (choice) {
case 1:
System.out.print("Enter element to Enqueue: ");
int element = sc.nextInt();
queue.enqueue(element);
break;
System.out.println("6. Is Empty?");
System.out.println("7. Exit");
choice = readInt(sc, "Enter your choice: ");

switch (choice) {
case 1:
int element = readInt(sc, "Enter element to Enqueue: ");
queue.enqueue(element);
break;

case 2:
queue.dequeue();
Expand All @@ -127,14 +143,14 @@ public static void main(String[] args) {
System.out.println(queue.isEmpty() ? "The Queue is Empty." : "The Queue is NOT Empty.");
break;

case 7:
System.out.println("Exiting...");
break;
default:
System.out.println("Invalid choice!");
}
} while (choice != 7);
case 7:
System.out.println("Exiting...");
break;

default:
System.out.println("Invalid choice. Please enter a valid menu option.");
}
} while (choice != 7);

sc.close();
}
Expand Down
86 changes: 51 additions & 35 deletions Data-Structures/Queue/Queue.java
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
import java.util.Scanner;

class Queue {
class Queue {
private int[] arr;
private int front;
private int rear;
Expand Down Expand Up @@ -74,17 +74,36 @@ public boolean isEmpty() {
return rear == -1;
}

public boolean isFull() {
return rear == capacity - 1;
}

public static void main(String[] args) {
Scanner sc = new Scanner(System.in);

System.out.print("Enter Queue size: ");
int capacity = sc.nextInt();

Queue queue = new Queue(capacity);
public boolean isFull() {
return rear == capacity - 1;
}

private static int readInt(Scanner sc, String prompt) {
while (true) {
System.out.print(prompt);
if (sc.hasNextInt()) {
return sc.nextInt();
}
System.out.println("Invalid input. Please enter an integer.");
sc.next();
}
}

private static int readPositiveInt(Scanner sc, String prompt) {
while (true) {
int value = readInt(sc, prompt);
if (value > 0) {
return value;
}
System.out.println("Invalid input. Please enter an integer greater than 0.");
}
}

public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int capacity = readPositiveInt(sc, "Enter Queue size: ");

Queue queue = new Queue(capacity);

while (true) {
System.out.println("\n--- Queue Operations ---");
Expand All @@ -93,18 +112,15 @@ public static void main(String[] args) {
System.out.println("3. Peek");
System.out.println("4. Display");
System.out.println("5. Is Full?");
System.out.println("6. Is Empty?");
System.out.println("7. Exit");
System.out.print("Enter your choice: ");

int choice = sc.nextInt();

switch (choice) {
case 1:
System.out.print("Enter element to Enqueue: ");
int element = sc.nextInt();
queue.enqueue(element);
break;
System.out.println("6. Is Empty?");
System.out.println("7. Exit");
int choice = readInt(sc, "Enter your choice: ");

switch (choice) {
case 1:
int element = readInt(sc, "Enter element to Enqueue: ");
queue.enqueue(element);
break;

case 2:
queue.dequeue();
Expand All @@ -126,14 +142,14 @@ public static void main(String[] args) {
System.out.println(queue.isEmpty() ? "The Queue is Empty." : "The Queue is NOT Empty.");
break;

case 7:
System.out.println("Exiting...");
sc.close();
return;
default:
System.out.println("Invalid choice!");
}
}
}
}
case 7:
System.out.println("Exiting...");
sc.close();
return;

default:
System.out.println("Invalid choice. Please enter a valid menu option.");
}
}
}
}
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