What is Encapsulation ?
- Encapsulation is the process of wrapping data(variables) and code (methods) together as a single unit . It hides the internal state of object from outside access, that mean the variable of a class will be hidden from other classes, and can be accessed only through method of current class. Encapsulation used to achieve data hiding ,not itself data hiding.
Why Use Encapsulation
- protects Data : keep important Fields are private (data-variable) safe from direct access.
- Hides Details : show only necessary thins to the user
- Controls Access:- gives control over who can read or change the data. that mean you can lock you data using private and you give a key (get/set method) to trusted one,only change authorized class or user.
- Easy to change: you can change the code inside without affecting other code and also you can use another project Encapsulated project
Achieving Encapsulation in java:-
Declare the variables of a class as private.
provide public setters(write-only) and getters(read-only) methods to modify and view the variables values.
Benefits of Encapsulation:-
The fields(global variable ) of class can be made read-only (or) write-only. class can have total control over what is stored in the fields.
Example:-
package encapsulation;
public class BankAccount {
// private variable - hidden from outside
private String accountHolderName;
private int accountNumber;
private double balance;
// constructor
BankAccount(String name ,int accNumber, double initialBalance)
{
this.accountHolderName=name;
this.accountNumber=accNumber;
if (initialBalance >=0)
{
this.balance=initialBalance;
}
else
{
System.out.println("Invalid blance! setto 0 by default. ");
this.balance=0;
}
}
public String getAccountHolderName()
{
return accountHolderName;
}
public void setAccountHolderName(String name)
{
if (name != null && !name.isEmpty())
{
this.accountHolderName= name;
}else
{
System.out.println("Invalid name!");
}
}
// Get balance (no direct access to variable)
public double getBalance()
{
return balance;
}
// withdraw method with check
public void deposit(double amount)
{
if (amount > 0 )
{
balance += amount;
System.out.println("Deposited: "+ amount);
}
else {
System.out.println("Invalid deposite amount! ");
}
}
// deposit method with validation
public void withdraw (double amount)
{
if (amount > 0 &&amount <= balance)
{
balance -= amount;
System.out.println(" Withdrawn:"+ amount);
}
else
{
System.out.println("Invalid funds");
}
}
//Display details (read-only)
public void displayAccountInfo()
{
System.out.println("Account Holder: "+ accountHolderName);
System.out.println("Account Number: "+ accountNumber );
System.out.println("Current Balance: "+ balance);
}
}
package encapsulation;
public class Bank_Main {
public static void main(String[] args) {
BankAccount account = new BankAccount("Prasanth",1001,5000);
account.displayAccountInfo();
account.deposit(1500);
account.displayAccountInfo();
//Trying to withdraw
account.withdraw(1500);
account.displayAccountInfo();
//trying to withdraw
account.withdraw(2000);
account.displayAccountInfo();
// Trying to set a bad name
account.setAccountHolderName("");
account.setAccountHolderName("sam");
System.out.println("updated name:" +account.getAccountHolderName());
//trying invalid operations
account.deposit(-500);
account.withdraw(10000); //more than balance
}
}
Encapsulation Read-only class
Example:2
package encapsulation;
// Creating Write-Only Class
public class FruitShop {
private String fruitname;
private int fruitprice;
public void setName(String name)
{
this.fruitname=name;
}
public void setfruitPrice(int price)
{
this.fruitprice=price;
}
}
package encapsulation;
// Creating Write-Only Class
public class FruitShop {
private String fruitname;
private int fruitprice;
public void setName(String name)
{
this.fruitname=name;
}
public void setfruitPrice(int price)
{
this.fruitprice=price;
}
}
Read and write:-
package encapsulation;
public class TechwaveEmployee {
private String emp_name;
private String emp_id;
private double net_salary;
TechwaveEmployee(String emp_name,String emp_id ,double net_salary)
{
this.emp_name =emp_name;
this.emp_id = emp_id;
this.net_salary = net_salary;
}
public String getEmp_name() {
return emp_name;
}
public void setEmp_name(String emp_name) {
this.emp_name = emp_name;
}
public String getEmp_id() {
return emp_id;
}
public void setEmp_id(String emp_id) {
this.emp_id = emp_id;
}
public double getNet_salary() {
return net_salary;
}
public void setNet_salary(double net_salary) {
this.net_salary = net_salary;
}
}
package encapsulation;
public class TechWaveHr {
public static void main(String[] args) {
// first object - setting values using constructor
TechwaveEmployee person1 = new TechwaveEmployee("Prasanth","Empl001",15000.00);
TechWaveHr person2 = new TechWaveHr();
// printing data
System.out.println("Employee (Initial values):");
System.out.println(person1.getEmp_id()+ " , "+ person1.getEmp_name()+" ," + person1.getNet_salary());
// updating values setter methods
person1.setEmp_id("Empl002");
person1.setEmp_name("Vishal");
person1.setNet_salary(50000.00);
//printing data
// printing data
System.out.println("Employee (Updated values):");
System.out.println(person1.getEmp_id()+ " , "+ person1.getEmp_name()+" ," + person1.getNet_salary());
}
}
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