Data hiding in Java - Step-by-Step Execution

Concept Flow - Data hiding

Start

↓

Define class with private variables

↓

Create public methods (getters/setters)

↓

Create object

↓

Access variables only via methods

↓

End

Data hiding means keeping variables private inside a class and accessing them only through public methods.

Execution Sample

Java

class Person {
  private String name;
  public void setName(String n) { name = n; }
  public String getName() { return name; }
}

public class Main {
  public static void main(String[] args) {
    Person p = new Person();
    p.setName("Anna");
    System.out.println(p.getName());
  }
}

This code hides the 'name' variable and accesses it only through setName and getName methods.

Execution Table

Step	Action	Variable/Method	Value/Result	Note
1	Create object	p	Person instance	Object p created
2	Call setter	setName("Anna")	name = "Anna"	Private variable 'name' set to 'Anna'
3	Call getter	getName()	"Anna"	Returns value of 'name'
4	Print output	System.out.println	Anna	Output is 'Anna'
5	Try direct access	p.name	Error	Cannot access private variable directly

💡 Execution stops after printing 'Anna' and error on direct access shows data hiding.

Variable Tracker

Variable	Start	After setName	After getName	Final
name	null	"Anna"	"Anna"	"Anna"

Key Moments - 3 Insights

Why can't we access the variable 'name' directly from the object?

Because 'name' is declared private, it is hidden from outside the class. Only methods inside the class can access it, as shown in step 5 of the execution_table.

How do we change the value of a private variable?

We use a public setter method like setName(), which changes the private variable inside the class, as shown in step 2.

How do we read the value of a private variable?

We use a public getter method like getName(), which returns the value, as shown in step 3.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'name' after step 2?

A Error

B null

C "Anna"

D "John"

💡 Hint

Check the 'After setName' column in variable_tracker and step 2 in execution_table.

At which step does the program print the value 'Anna'?

A Step 3

B Step 4

C Step 2

D Step 5

💡 Hint

Look at the 'Print output' action in execution_table.

If the variable 'name' was public, what would happen at step 5?

A Direct access allowed, no error

B Error because variable is private

C Setter method called automatically

D Getter method called automatically

💡 Hint

Step 5 shows error due to private access; if public, direct access would work.

Concept Snapshot

Data hiding means making class variables private.
Access them only via public getter and setter methods.
Prevents outside code from changing variables directly.
Helps protect data and control how it changes.
Use private keyword for variables, public for methods.

Full Transcript

Data hiding in Java means keeping variables private inside a class so that they cannot be accessed directly from outside. Instead, public methods called getters and setters are used to read and change these variables. In the example, the variable 'name' is private. We create a Person object 'p'. We set the name using p.setName("Anna") which changes the private variable inside the class. Then we get the name using p.getName() which returns the value. Trying to access p.name directly causes an error because it is private. This protects the data and controls how it is accessed or changed.