feat: Add Subject1 and Student1 classes to model subjects and students with encapsulation

WHAT the code does:
Defines Subject1 with private fields:
- subID, name, maxMarks, marksObtain.
- Constructor initializes subID, name, and maxMarks.
- Getters and setters provide controlled access.
- isQualified() checks if marks are ≥ 40% of max marks.
- toString() returns formatted subject details.

Defines Student1 with private fields:
- rollNo, name, dept, numOfSub, and an array of Subject references.
- Overloaded constructors initialize rollNo, name, and optionally number of subjects.
- Getters return student info and associated subjects.
- setDept() assigns department.
- setSubjects(Subject... subs) assigns subjects to the student.
- toString() formats student details.

Defines OOPsIMP with main():
- Creates an array of 3 Subject objects (DS, Algorithms, OS).
- Prints subject details.

WHY this matters:
Demonstrates object composition: a Student1 contains multiple Subject references.
Illustrates encapsulation through private fields and getters/setters.
Shows constructor overloading for flexible object creation.
Introduces array-of-objects concept in OOP design.

HOW it works:
OOPsIMP creates Subject objects and prints them using toString().
Student1 is designed to associate with multiple Subject objects, but this link is not yet used in main().
Validation logic (40% threshold) is encoded in isQualified() for subject performance checks.

Tips and gotchas:
OOPsIMP uses Subject, but the defined class is Subject1 — likely a naming mismatch that will cause compilation errors.
Student1’s sub array is declared but never initialized; setSubjects() will throw NullPointerException. It should be initialized with new Subject[numOfSub].
isQualified() uses integer division (maxMarks/10*4), which may cause precision issues; prefer (maxMarks * 40) / 100.
Currently, no setters exist for subID or name in Subject1, making them immutable after construction — which may be intentional.

Use-cases:
Educational demonstration of OOP composition, encapsulation, and constructor overloading.
Models a simple academic system linking students and subjects.
Foundation for expanding into grading systems, course registration, or transcript generation.

Short key: class-subject1 student1 oop composition encapsulation.

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

Author: Someshdiwan

Section11ObjectOrientedProgramming/src/OOPsIMP.java

@@ -1,58 +1,50 @@
-//Pending solve it again
-
-class Subject1
-{
+class Subject1 {
     private String subID;
     private String name;
     private int maxMarks;
     private int marksObtain;
 
-    public Subject1(String subID,String name,int maxMarks)
-    {
+    public Subject1(String subID,String name,int maxMarks) {
         this.subID=subID;
         this.name=name;
         this.maxMarks=maxMarks;
     }
+
     public String getSubID(){return subID;}
     public String getName(){return name;}
     public int getMaxMarks(){return maxMarks;}
     public int getMarksObtain(){return marksObtain;}
 
-    public void setMaxMarks(int mm)
-    {
+    public void setMaxMarks(int mm) {
         maxMarks=mm;
     }
-    public void setMarksObtain(int m)
-    {
+
+    public void setMarksObtain(int m) {
         marksObtain=m;
     }
-    boolean isQualified()
-    {
+
+    boolean isQualified() {
         return marksObtain>=maxMarks/10*4;
     }
-    public String toString()
-    {
+
+    public String toString() {
         return "\nSubject ID:"+subID+"\nName :"+name+"\nMarks Obtained: "+marksObtain;
     }
 }
 
-class Student1
-{
+class Student1 {
     private String rollNo;
     private String name;
     private String dept;
     private int numOfSub;
     private Subject sub[];
 
-
-    public Student1(String roll,String name)
-    {
+    public Student1(String roll,String name) {
         this.rollNo=roll;
         this.name=name;
-
     }
-    public Student1(String roll,String name,int ns)
-    {
+
+    public Student1(String roll,String name,int ns) {
         this.rollNo=roll;
         this.name=name;
         this.numOfSub=ns;
@@ -64,28 +56,22 @@ public Student1(String roll,String name,int ns)
     public int getNoOfSubjects(){return numOfSub;}
     public Subject[] getSubjects(){return sub;}
 
-    public void setDept(String dept)
-    {
+    public void setDept(String dept) {
         this.dept=dept;
     }
-    public void setSubjects(Subject ...subs)
-    {
+
+    public void setSubjects(Subject ...subs) {
         for(int i=0;i<subs.length;i++)
             sub[i]=subs[i];
     }
 
-    public String toString()
-    {
+    public String toString() {
         return "Roll :" +rollNo+"\nName :"+name+"\nDept :"+dept;
     }
-
 }
 
-public class OOPsIMP
-{
-
-    public static void main(String[] args)
-    {
+public class OOPsIMP {
+    public static void main(String[] args) {
         Subject subs[]=new Subject[3];
         subs[0]=new Subject("s101","DS",100);
         subs[1]=new Subject("s102","Algorithms",100);
@@ -94,4 +80,4 @@ public static void main(String[] args)
         for(Subject s:subs)
             System.out.println(s);
     }
-}
+}