CRUD Operations in Java

CRUD stands for Create, Read/Retrieve, Update, and Delete, which are the fundamental operations carried out on persistent storage. CRUD involves the use of standardized HTTP methods and is focused on data operations. CRUD operations are data-centric and align with the standardized utilization of HTTP methods. CRUD operations in Java refer to the fundamental operations you can perform on data in a database or data structure. These operations are necessary for maintaining and modifying data in a wide range of applications, from simple managing database systems to complex data storage systems.

These are the standard CRUD operations:

POST: The technique is used to send data to a certain resource to be processed. On the server, a new resource is created.
GET: The method requests data from a specified resource. It takes existing data from the server and reads or retrieves it without changing it.
PUT: The method updates existing data on the server. It sends data to be stored at a specific resource location, replacing the resource's current content.
DELETE: The method is used to remove data from a specified resource. The resource is removed from the server and is no longer accessible as a result.

Make a menu with the following four basic operations: Add, Search, Remove, and Show Student Details.

Explanation of each operation:

Create (C):

When performing the "Create" procedure, new data records are added to a data storage.
In Java, this typically involves inserting new records into a database or adding new objects to a collection or data structure.
For databases, you can use SQL statements (e.g., INSERT INTO) or Object-Relational Mapping (ORM) frameworks like Hibernate or JPA to create records.

Read (R):

The "Read" operation is about retrieving data from a data store.
Java allows you to access data from a variety of sources, including external APIs, files, and databases.
For databases, you can use SQL queries (e.g., SELECT) or Java libraries like JDBC to retrieve data.
Reading data from files involves file I/O operations, and for external APIs, you use HTTP requests and JSON/XML parsing to fetch and parse data.

Update (U):

To modify already-existing data records, utilize the "Update" operation.
In Java, you can update data in a database by executing SQL statements (e.g., UPDATE) or using ORM frameworks.
For collections or data structures, you directly update the objects by modifying their attributes.

Delete (D):

The "Delete" procedure includes deleting data records from a data the server.
In Java, you can delete data from a database using SQL statements (e.g., DELETE FROM) or ORM frameworks.
For collections or data structures, you remove objects or elements from the collection.

CRUD Operations for Student Management System in Java

A Student Management System is a crucial application in educational institutions that allows efficient management of student data. The fundamental capabilities which allow for the processing of this data within a database are known as CRUD operations (Create, Read, Update, and Delete). There will be four primary choices on the menu: Add, Search, Remove, and Display student information.

Files to be created:

1. StudentRecordLinkedList.java:

StudentRecordLinkedList.java serves as the main program file. It handles user interaction through a menu-driven approach, allowing users to add, delete, update, search, and display student records. The class instantiates the StudentRecordManagement class and provides a user interface for managing student data.

2. StudentRecordManagement.java:

StudentRecordManagement.java contains the StudentRecordManagement class, which encapsulates the logic for managing student records. It includes methods to add, delete, update, search, and display student records using a LinkedList data structure. The class ensures operations like adding new records, updating existing ones, and searching for records based on user input.

3. Record.java:

Record.java defines the `Record` class, representing individual student records. It includes private instance variables for name, idNumber, and contactNumber, along with constructors, getters, setters, and a toString() method. This class encapsulates the data structure for each student record, enabling the program to store and manipulate student information effectively.

Algorithm:

Step 1: Initialize Classes and Imports

Import necessary Java packages: Java.util.Scanner and Java.util.LinkedList.
Define a class Record with private instance variables for name, idNumber, and contactNumber.
Implement constructors, getters, setters, and toString() method for the Record class.

Step 2: Create StudentRecordManagement Class

Define a class StudentRecordManagement to manage student records.
Declare a LinkedList of Record objects.
Implement methods within the class for add, delete, update, search, and display operations.

Step 3: Main Method Initialization

Inside StudentRecordManagement class, create the main method.
Instantiate StudentRecordManagement class.
Hard code a sample student record and add it to the linked list.

Step 4: User Menu

Implement a simple text-based menu for user interaction with options:

Add a new student record.
Delete a student record that already exists.
Update the existing record of the student.
Search for a student record.
Display all student records.
Exit the program.

Step 5: User Input Handling

Use the Scanner class to handle user input for various operations.

Step 6: Implement Add Operation

Prompt user for student information (ID number, contact number, name).
Please create a new Record object with the provided data and add it to the linked list.

Step 7: Implement Delete Operation

Prompt the user for the ID number of the student to be deleted.
Search the linked list for the student record with the given ID number and remove it.

Step 8: Implement Update Operation

Prompt the user for the ID number of the student to be updated.
Search the linked list for the student record with the given ID number.
Prompt users for new information and update the student record.

Step 9: Implement Search Operation

Prompt the user for the ID number of the student to be searched.
Search the linked list for the student record with the given ID number and display it if found.

Step 10: Implement Display Operation

Iterate through the linked list and print each student record.

Implementation

Filename: StudentRecordLinkedList.java

package College;

// Java Program to Illustrate StudentRecordLinkedList Class

// Importing required classes
import java.util.Scanner;

// Class
public class StudentRecordLinkedList {

	// Main driver method
	public static void main(String[] args)
	{

		// Creating the object StudentRecordManagement.
		StudentRecordManagement hr = new StudentRecordManagement();

		// Creating a Record object.
		Record record = new Record();
	
		// Initial Employee record
		// Using mutators to hard code the data
		record.setIdNumber(4238);
		record.setContactNumber(89770);
		record.setName("Surya");

		// Calling add() method to add static data (Hard Coded Data) to linked List
		hr.add(record);

		// Creating Scanner Object to read input
		Scanner input = new Scanner(System.in);

		// Creating an integer variable to store the user's choice
		int option = 0;

		// Do - While loop for menu-driven program
		do {
			// Display the menu
			menu();
			option = input.nextInt();

			// Switch case to handle user's choice
			switch (option) {

			// Case 1: Add Student
			case 1:

				// Prompt user for Student information
				System.out.print("What is the Student id Number? ");
				int idNumber = input.nextInt();

				System.out.print("What is the Student contact Number? ");
				long contactNumber = input.nextLong();
				input.nextLine(); // Consume the newline character

				System.out.print("What is the Student Name? ");
				String name = input.nextLine();

				// Create a new Record object and pass constructor parameters.
				record = new Record(name, idNumber, contactNumber);
				// Call the add() method
				hr.add(record);
				System.out.println(record.toString());

				// Break statement used to exit the switch case
				break;

			// Case 2: Delete Student
			case 2:

				// Prompt user for Student id to delete
				System.out.print("What is the Student id number? ");
				int rId = input.nextInt();

				// Invoke the delete() method to remove the record
				hr.delete(rId);

				break;

			// Case 3: Update Student
			case 3:

				// Prompt user for Student id to update
				System.out.print("What is the Student id number? ");
				int rIdNo = input.nextInt();
				hr.update(rIdNo, input);

				break;

			// Case 4: Search Student
			case 4:

				// Prompt user for Student id to search
				System.out.print("What is the Student id? ");
				int bookId = input.nextInt();

				if (!hr.find(bookId)) {
					System.out.println("Student id does not exist\n");
				}

				break;

			// Case 5: Display Students
			case 5:
				hr.display();
				break;

			// Case 6: Exit program
			case 9:

				// Display exit message and terminate the program
				System.out.println("\nThanks for using the Student Record Management System. Have a great day!\n");
				System.exit(0);

				break;

			// Case 7: Default case
			// If none of the above cases execute
			default:

				// Print an error message for invalid input
				System.out.println("\nInvalid input\n");
				break;
			}
		}

		// Continue the loop until the user chooses to exit (option 9)
		while (option != 9);
	}

	// Method 2
	// Menu - Static menu for displaying options
	public static void menu()
	{

		// Printing statements displaying the menu on the console
		System.out.println("MENU");
		System.out.println("1: Add Student");
		System.out.println("2: Delete Student");
		System.out.println("3: Update Student");
		System.out.println("4: Search Student");
		System.out.println("5: Display Students");
		System.out.println("9: Exit program");
		System.out.print("Enter your selection : ");
	}
}

Filename: StudentRecordManagement.java

package College;

// Java Program to Illustrate StudentRecordManagement Class

// Importing required classes
import java.util.LinkedList;
import java.util.Scanner;

// Class
public class StudentRecordManagement {

    // Creating an empty LinkedList to store records
    LinkedList<Record> list;

    // Default Constructor
    public StudentRecordManagement() {
        list = new LinkedList<>(); // Initialize the linked list
    }

    // Method 1
    // Adding Record
    // @param record
    public void add(Record record) {

        // Checking if a record already exists or not,
        //If not, add it to the Record list; otherwise,
        // display an error message
        if (!find(record.getIdNumber())) {
            list.add(record);
        } else {

            // Print statement
            System.out.println("Record already exists in the Record list");
        }
    }

    // Method 2
    // Searching Record
    // @param idNumber
    // @return
    public boolean find(int idNumber) {

        // Iterating over the record list using a for-each loop
        for (Record l : list) {

            // Checking if a record with the given idNumber exists
            if (l.getIdNumber() == idNumber) {

                // Print the found record
                System.out.println(l);
                return true;
            }
        }
        return false; // Return false if the record is not found
    }

    // Method 3
    // Delete Record
    // @param recIdNumber
    public void delete(int recIdNumber) {
        Record recordDel = null;

        // Iterating over the record list
        for (Record ll : list) {

            // Finding the record to be deleted by id Number
            if (ll.getIdNumber() == recIdNumber) {
                recordDel = ll;
            }
        }

        // If recordDel is null, then show an error message,
        //Otherwise, remove the record from the Record list
        if (recordDel == null) {

            // Displaying a message for an invalid record ID
            System.out.println("Invalid record Id");
        } else {

            list.remove(recordDel);

            // Display a message for the successful deletion of the record
            System.out.println("Successfully removed record from the list");
        }
    }

    // Method 4
    // Finding Record
    // @param idNumber
    // @return
    public Record findRecord(int idNumber) {

        // Iterate over the Record list using a for-each loop
        for (Record l : list) {

            // Checking if a record with the given id Number exists
            if (l.getIdNumber() == idNumber) {
                return l; // Return the found record
            }
        }

        return null; // Return null if the record is not found
    }

    // Method 5
    // Update Record
    // @param id
    // @param input
    public void update(int id, Scanner input) {

        if (find(id)) {
            Record rec = findRecord(id);

            // Display a message only
            System.out.print("What is the new Student id Number? ");
            int idNumber = input.nextInt();

            // Display a message only
            System.out.print("What is the new Student contact Number? ");
            long contactNumber = input.nextLong();
            input.nextLine();

            // Display a message only
            System.out.print("Please enter the updated student's name: ");
            String name = input.nextLine();

            // Update the record with new values
            rec.setIdNumber(idNumber);
            rec.setName(name);
            rec.setContactNumber(contactNumber);
            System.out.println("Record Updated Successfully");
        } else {

            // Print statement
            System.out.println("Record Not Found in the Student list");
        }
    }

    // Method 6
    // Display Records
    public void display() {

        // If the record list is empty, then
        // print the message below
        if (list.isEmpty()) {

            // Print statement
            System.out.println("The list has no records\n");
        }

        // Iterating over the Record list using a for-each loop
        for (Record record : list) {

            // Printing the record details
            System.out.println(record.toString());
        }
    }
} 

Filename: Record.java

package College;

// Class
public class Record {

    // Instance variables
    private String name;
    private int idNumber;
    private long contactNumber; // Change the type to long

    // Default Constructor
    public Record() {}

    // Parameterized Constructor
    // @param name - The name of the record
    // @param idNumber - The ID number of the record
    // @param contactNumber - The contact number of the record
    public Record(String name, int idNumber, long contactNumber) // Change the type to long
    {

        // this keyword refers to the current instance itself
        this.name = name;
        this.idNumber = idNumber;
        this.contactNumber = contactNumber;
    }

    // Getting the value of contactNumber
    // @return the value of contactNumber
    public long getContactNumber() { return contactNumber; } // Change the return type to long

    // Set the value of contactNumber
    // @param contactNumber - The new value of contactNumber
    public void setContactNumber(long contactNumber) // Change the type to long
    {
        this.contactNumber = contactNumber;
    }

    // Getting the value of idNumber
    // @return the value of idNumber
    public int getIdNumber() { return idNumber; }

    // Setting the value of idNumber
    // @param idNumber - The new value of idNumber
    public void setIdNumber(int idNumber)
    {
        this.idNumber = idNumber;
    }

    // Getting the value of name
    // @return the value of name
    public String getName() { return name; }

    // Setting the value of name
    // @param name - The new value of name
    public void setName(String name) { this.name = name; }

    // toString() Method
    // @return - A string representation of the record
    @Override
    public String toString()
    {

        // Returning the record as a formatted string
        return "Record{" +
            "name='" + name + '\'' +
            ", idNumber=" + idNumber +
            ", contactNumber=" + contactNumber +
            '}';
    }
}

Output:

Add