10 b)
import java.util.Hashtable;
import java.util.Scanner;
class HashTableRemoveDuplicateKeys {
public static void main(String... args) {
// Create a Hashtable to store the data
Hashtable<Integer, String> ht = new Hashtable<>();
Scanner scanner = new Scanner(System.in);
// Prompt the user to enter the number of elements they want to insert
System.out.println("How many elements do you want to insert?");
int size = scanner.nextInt();
scanner.nextLine(); // Consume the newline character
// Inserting data dynamically into the Hashtable
for (int i = 0; i < size; i++) {
System.out.println("Enter Student ID (Key): ");
int studentId = scanner.nextInt();
scanner.nextLine(); // Consume the newline character
// Check if the key already exists in the Hashtable
if (ht.containsKey(studentId)) {
System.out.println("Duplicate key found! The student ID already exists.");
} else {
System.out.println("Enter Student Name (Value): ");
String studentName = scanner.nextLine();
ht.put(studentId, studentName); // Insert the key-value pair
System.out.println("Student added successfully!");
}
}
// Printing the elements of the Hashtable after all insertions
System.out.println("\nFinal Hashtable (without duplicates): ");
printHashtable(ht);
scanner.close(); // Close the scanner object after use
}
// Helper method to print the Hashtable contents
public static void printHashtable(Hashtable<Integer, String> ht) {
for (Integer key : ht.keySet()) {
System.out.println("Student ID: " + key + " -- Student Name: " + ht.get(key));
}
}
}
Out put:
How many elements do you want to insert?
3
Enter Student ID (Key):
101
Enter Student Name (Value):
John Doe
Student added successfully!
Enter Student ID (Key):
102
Enter Student Name (Value):
Jane Smith
Student added successfully!
Enter Student ID (Key):
101
Duplicate key found! The student ID already exists.
Final Hashtable (without duplicates):
Student ID: 101 -- Student Name: John Doe
Student ID: 102 -- Student Name: Jane Smith
(or)
import java.util.Hashtable;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
class RemoveDuplicateValues {
public static void main(String[] args) {
// Create a Hashtable and add some entries (with possible duplicate values)
Hashtable<Integer, String> ht = new Hashtable<>();
ht.put(1, "John");
ht.put(2, "Jane");
ht.put(3, "John"); // Duplicate value "John"
ht.put(4, "Alice");
ht.put(5, "Bob");
ht.put(6, "Alice"); // Duplicate value "Alice"
System.out.println("Original Hashtable:");
printHashtable(ht);
// Remove duplicates based on values
Hashtable<Integer, String> uniqueHashtable = removeDuplicates(ht);
System.out.println("\nHashtable after removing duplicate values:");
printHashtable(uniqueHashtable);
}
// Function to remove duplicate values from the Hashtable
public static Hashtable<Integer, String> removeDuplicates(Hashtable<Integer, String> ht) {
// Create a new Hashtable to store unique key-value pairs
Hashtable<Integer, String> uniqueHashtable = new Hashtable<>();
// Use a HashSet to track unique values
Set<String> uniqueValues = new HashSet<>();
// Iterate over the original Hashtable
for (Map.Entry<Integer, String> entry : ht.entrySet()) {
String value = entry.getValue();
// If the value is not already in the HashSet, add it to the new Hashtable
if (!uniqueValues.contains(value)) {
uniqueHashtable.put(entry.getKey(), value);
uniqueValues.add(value); // Mark this value as encountered
}
}
return uniqueHashtable; // Return the new Hashtable with unique values
}
// Helper function to print the Hashtable
public static void printHashtable(Hashtable<Integer, String> ht) {
for (Map.Entry<Integer, String> entry : ht.entrySet()) {
System.out.println("ID: " + entry.getKey() + ", Name: " + entry.getValue());
}
}
}
Output:
Original Hashtable:
ID: 1, Name: John
ID: 2, Name: Jane
ID: 3, Name: John
ID: 4, Name: Alice
ID: 5, Name: Bob
ID: 6, Name: Alice
Hashtable after removing duplicate values:
ID: 1, Name: John
ID: 2, Name: Jane
ID: 4, Name: Alice
ID: 5, Name: Bob
10 c
import java.util.TreeMap;
import java.util.Map;
import java.util.Set;
import java.util.Iterator;
public class TreeMapIteration {
public static void main(String[] args) {
// Create a TreeMap and insert some entries
TreeMap<Integer, String> treeMap = new TreeMap<>();
treeMap.put(1, "John");
treeMap.put(3, "Jane");
treeMap.put(2, "Alice");
treeMap.put(4, "Bob");
// 1. Iterating using for-each loop with entrySet()
System.out.println("Iterating using for-each with entrySet():");
for (Map.Entry<Integer, String> entry : treeMap.entrySet()) {
System.out.println("Key: " + entry.getKey() + ", Value: " + entry.getValue());
}
// 2. Iterating using for-each loop with keySet()
System.out.println("\nIterating using for-each with keySet():");
for (Integer key : treeMap.keySet()) {
System.out.println("Key: " + key + ", Value: " + treeMap.get(key));
}
// 3. Iterating using for-each loop with values()
System.out.println("\nIterating using for-each with values():");
for (String value : treeMap.values()) {
System.out.println("Value: " + value);
}
// 4. Iterating using Iterator with entrySet()
System.out.println("\nIterating using Iterator with entrySet():");
Iterator<Map.Entry<Integer, String>> iterator = treeMap.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry<Integer, String> entry = iterator.next();
System.out.println("Key: " + entry.getKey() + ", Value: " + entry.getValue());
}
}
}
Output:
Iterating using for-each with entrySet():
Key: 1, Value: John
Key: 2, Value: Alice
Key: 3, Value: Jane
Key: 4, Value: Bob
Iterating using for-each with keySet():
Key: 1, Value: John
Key: 2, Value: Alice
Key: 3, Value: Jane
Key: 4, Value: Bob
Iterating using for-each with values():
Value: John
Value: Alice
Value: Jane
Value: Bob
Iterating using Iterator with entrySet():
Key: 1, Value: John
Key: 2, Value: Alice
Key: 3, Value: Jane
Key: 4, Value: Bob
