feat: Add DemoDataHidding with encapsulated fields and validation for rectangle properties

WHAT the code does:
Defines DemoDataHidding with private fields length and breadth.
Provides public getters and setters:
- getLength(), getBreadth() return field values.
- setLength(double l), setBreadth(double b) assign values, defaulting to 0 if negative.
Implements methods:
- area(): computes length × breadth.
- perimeter(): computes 2 × (length + breadth).
- isSquare(): returns true if length == breadth.
Defines DataHidding with main():
- Attempts to create a Rectangle object, set dimensions, and print computed values.

WHY this matters:
Demonstrates data hiding by using private fields with controlled access through getters and setters.
Validates inputs to prevent invalid states (e.g., negative dimensions).
Models real-world rectangle properties with simple methods for area, perimeter, and square check.
Highlights encapsulation as a core OOP principle.

HOW it works:
When positive values are set via setters, the fields are updated normally.
If negative values are provided, the setters assign 0 instead.
area() and perimeter() compute rectangle geometry.
isSquare() compares length and breadth for equality.

Tips and gotchas:
The DataHidding class references Rectangle, which does not exist; it should reference DemoDataHidding instead.
Comparing doubles with == in isSquare() may be unsafe due to floating-point precision issues; use a tolerance (e.g., Math.abs(a-b) < 1e-9).
Encapsulation could be further strengthened by using constructors for required fields instead of relying only on setters.
Overriding toString() would make printing object details cleaner.

Use-cases:
Educational example of encapsulation and data hiding in Java.
Demonstrates geometry modeling with validation.
Foundation for building robust shapes and geometry classes in larger applications.

Short key: class-demodatahidding encapsulation rectangle-validation.

Signed-off-by: https://github.com/Someshdiwan <[email protected]>

Author: Someshdiwan

Section11ObjectOrientedProgramming/src/DataHidding.java

@@ -1,60 +1,48 @@
-class DemoDataHidding
-{
+class DemoDataHidding {
     private double length;
     private double breadth;
 
-    public double getLength()
-    {
+    public double getLength() {
         return length;
     }
 
-    public double getBreadth()
-    {
+    public double getBreadth() {
         return breadth;
     }
 
-    public void setLength(double l)
-    {
+    public void setLength(double l) {
         if(l>=0)
             length=l;
         else
             length=0;
     }
 
-    public void setBreadth(double b)
-    {
+    public void setBreadth(double b) {
         if(b>=0)
             breadth=b;
         else
             breadth=0;
     }
 
-    public double area()
-    {
+    public double area() {
         return getLength()*getBreadth();
     }
 
-    public double perimeter()
-    {
+    public double perimeter() {
         return 2*(length+breadth);
     }
 
-    public boolean isSquare()
-    {
+    public boolean isSquare() {
         if(length==breadth)
             return true;
         else
             return false;
     }
 }
-
-
-public class DataHidding
-{
-
+public class DataHidding {
     public static void main(String[] args) {
         Rectangle r=new Rectangle();
-        r.setLength(10.5);//check with negative values.
+        r.setLength(10.5); //check with negative values.
         r.setBreadth(5.5);
 
         System.out.println("Area "+r.area());
@@ -64,4 +52,4 @@ public static void main(String[] args) {
         System.out.println("Length "+r.getLength());
         System.out.println("Breadth "+r.getBreadth());
     }
-}
+}