feat: Add Subject class and ArrayOfObject demo for handling multiple objects in arrays

WHAT the code does:
Defines a Subject class with fields:
- subID, name, maxMarks, marksObtains.
Constructor initializes subID, name, and maxMarks.
Provides getters and setters for encapsulated access.
Implements isQualified() to check if marks obtained are at least 40% of max marks.
Overrides toString() to display subject details.
Defines ArrayOfObject with main():
- Creates an array of Subject objects.
- Initializes three subjects (DS, Algorithms, Operating Systems).
- Iterates over the array and prints each Subject.

WHY this matters:
Demonstrates how arrays can store multiple objects in Java.
Encapsulates object state with private fields and exposes controlled access through methods.
Highlights object initialization via constructors and usage of overridden toString() for formatted output.
Introduces a simple grading rule (40% threshold) through isQualified().

HOW it works:
Subject subs[] = new Subject[3] creates an array of references.
Each index is assigned a new Subject object.
Enhanced for loop iterates through the array, printing details via toString().
Output shows subject IDs, names, and marksObtains (default 0 unless explicitly set).

Tips and gotchas:
marksObtains defaults to 0 because it’s never set before printing; consider using setMarksObtain().
isQualified() currently uses integer division in maxMarks/10*4, which may behave unexpectedly for non-multiples of 10; use (maxMarks * 40) / 100 instead.
Overriding toString() is effective, but adding subject maxMarks could improve clarity.
For real systems, prefer List<Subject> instead of fixed arrays for flexibility.

Use-cases:
Educational example of arrays of objects in Java.
Useful for modeling student-subject relationships in simple academic systems.
Foundation for extending into collections-based applications like gradebooks or course management tools.

Short key: class-subject arrayofobject encapsulation object-array.

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

Author: Someshdiwan

Section11ObjectOrientedProgramming/src/ArrayOfObject.java

@@ -1,20 +1,20 @@
-//You have to wtite a 2 classes one is subject and students.
-//you have to write a class for subject and subjID and name and maxMarks and maxobtain. you have to decide the data type and properties methods and constructers. how many constructer are possible.
-//data type Should be a string for subID and name also and MaxMarks is Int and MarksObtain is als.
-//Property methods get method for all of them... what about the set method
-//maxmarks can change everytime so marksobtain are also use the set method
-//constructer you can not have non parameterized cons.. subject(sid, name) and subject(",",max marks, marks obtain)
-
-
-class Subject
-{
+/*
+You have to write a 2 classes one is subject and students.
+you have to write a class for subject and subjID and name and maxMarks and maxobtain.
+you have to decide the data type and properties methods and constructers. how many constructer are possible.
+data type Should be a string for subID and name also and MaxMarks is Int and MarksObtain is als.
+Property methods get method for all of them... what about the set method
+maxmarks can change everytime so marksobtain are also use the set method
+constructer you can not have non parameterized cons.. subject(sid, name) and subject(",",max marks, marks obtain)
+*/
+
+class Subject {
     private String subID;
     private String name;
     private int maxMarks;
     private int marksObtains;
 
-    public Subject(String subID,String name,int maxMarks)
-    {
+    public Subject(String subID,String name,int maxMarks) {
         this.subID=subID;
         this.name=name;
         this.maxMarks=maxMarks;
@@ -25,33 +25,25 @@ public Subject(String subID,String name,int maxMarks)
     public int getMaxMarks(){return maxMarks;}
     public int getMarksObtains(){return marksObtains;}
 
-    public void setMaxMarks(int mm)
-    {
+    public void setMaxMarks(int mm) {
         maxMarks=mm;
     }
 
-    public void setMarksObtain(int m)
-    {
+    public void setMarksObtain(int m) {
         marksObtains=m;
     }
 
-    boolean isQualified()
-    {
+    boolean isQualified() {
         return marksObtains>=maxMarks/10*4;
     }
 
-    public String toString()
-    {
+    public String toString() {
         return"\n SubjectID: "+subID+"\n Name "+name+"\n MarksObtained "+marksObtains;
     }
-
 }
 
-public class ArrayOfObject
-{
-
-    public static void main(String[] args)
-    {
+public class ArrayOfObject {
+    public static void main(String[] args) {
         //Array of objects
         //Subs Reference to an object
         //Pointers or References 0, 1, 2. there are no pointers in JAVA.
@@ -67,4 +59,4 @@ public static void main(String[] args)
         for(Subject s:subs)
             System.out.println(s);
     }
-}
+}