From 42f488f987b06e01cee8766a1de5f0323309af2a Mon Sep 17 00:00:00 2001
From: Bobcat <bobcatsinful@gmail.com>
Date: Mon, 5 Jan 2026 20:17:15 +0530
Subject: [PATCH 1/4] add perni

---
 PYQ/TNTYFIV/Colsum.java | 22 +++++++++++++
 PYQ/TNTYFIV/Perni.java  | 54 +++++++++++++++++++++++++++++++
 README.md               | 71 +++++++++++++++++++++++++++++++++++++++--
 3 files changed, 145 insertions(+), 2 deletions(-)
 create mode 100644 PYQ/TNTYFIV/Colsum.java
 create mode 100644 PYQ/TNTYFIV/Perni.java

diff --git a/PYQ/TNTYFIV/Colsum.java b/PYQ/TNTYFIV/Colsum.java
new file mode 100644
index 0000000..7618007
--- /dev/null
+++ b/PYQ/TNTYFIV/Colsum.java
@@ -0,0 +1,22 @@
+public class Colsum {
+    int mat[][] , m , n;
+    Colsum(int mm, int nn)
+    {
+        m = mm;
+        n = nn;
+        mat = new int[m][n];
+    }
+    void readArray()
+    {
+        for (int i = 0; i <= m; i++)
+        {
+            for (int j = 0; j <= n; j++) {
+                System.out.print("Enter element for "+i+"th row and "+j+"th column:");
+                mat[i][j] = x.nextInt;
+                
+                
+            }    
+        }
+
+    }
+}
diff --git a/PYQ/TNTYFIV/Perni.java b/PYQ/TNTYFIV/Perni.java
new file mode 100644
index 0000000..61402f7
--- /dev/null
+++ b/PYQ/TNTYFIV/Perni.java
@@ -0,0 +1,54 @@
+import java.util.Scanner;
+
+public class Perni
+{
+    static int num; //to store a binary number
+    
+    Perni()
+    {
+        num = 0;
+    }
+    static void accept()
+    {
+        Scanner x = new Scanner(System.in);
+        System.out.println("Enter a bunary number");
+        num = x.nextInt();
+        x.close();
+        
+        int t = num;
+        while(t!=0)
+        {
+            int d = t%10;
+            if (d!=0 && d!=1)
+            {
+                System.out.println("INVALID INPUT");
+                System.exit(0);
+            }
+            t = t/10;
+        }
+    }
+
+    static int countOne(int k)
+    {
+    
+        if(k==0) return 0;
+        return (k%10)+countOne(k/10);
+        
+        // if(k==0) return 0;
+        // return (k%10 == 1?1:0) + countOne(k/10);
+    }
+    
+    static void check()
+    {
+        int c = countOne(num);
+        if (c%2!=0) System.out.println("Perni Number");
+        else System.out.println("Not Perni Number");
+    }
+
+    public static void main(String[] args)
+    {
+        Perni ob = new Perni();
+        Perni.accept();
+        Perni.check();
+    }
+}
\ No newline at end of file
diff --git a/README.md b/README.md
index da0aa20..6a77a8d 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,69 @@
-# Studying Java
- java projects for school
+# 📚 Java Practice Collection
+A growing library of small Java programs that illustrate core language concepts – loops, conditionals, arrays, classes, inheritance, I/O, and more.
+
+Why this repo?
+• 100+ self‑contained examples written while learning Java (2018‑2023).
+• Ready to copy‑paste, compile, run, or import into any IDE.
+• All files are plain .java – no external dependencies or build tools required.
+
+📁 Folder Overview
+Folder	Typical Contents / Purpose
+bin/	Compiled .class files (generated automatically by javac). No source code lives here.
+Class12Project/	Exercises from a 12th‑grade curriculum (e.g., simple programs, loops, conditionals).
+for_loop/	Programs that demonstrate for, while, and do‑while loops – e.g., alphabet printing, array iteration.
+if-else/	Examples of conditional logic (if/else, switch) plus small utility programs (electricity bill calculator, date converter).
+Inheritance/	Basic class hierarchies that show inheritance, method overriding, and simple object models (Account, Bank, etc.).
+PYQ/TNTYFIV/	Practice questions from programming contests. Contains the Colsum column‑sum calculator and the Perni binary‑number checker.
+switch_case/	Programs that heavily use Java’s switch statement (date converters, menu systems, etc.).
+Tip: All source files are plain Java (.java). No external dependencies or build tools required.
+
+⚙️ How to Compile & Run
+The following one‑liner compiles every .java file in the repository and places the resulting .class files alongside their sources:
+
+Potentially dangerous command
+Bash
+Run
+find . -name "*.java" | xargs javac
+After compilation, run any program by specifying its fully‑qualified class name (the directory path is used as the package prefix because no explicit package statements are present):
+
+Potentially dangerous command
+Bash
+Run
+### Example: run Colsum
+cd PYQ/TNTYFIV
+java Colsum
+
+### Run a for‑loop example
+java for_loop.Alphabets2
+Why this stays future‑proof
+• Adding new .java files automatically picks them up – no manual edits.
+• The run command never changes because it relies only on the file name, not an explicit list.
+
+📖 Program Highlights
+Folder	Example	What it teaches
+for_loop	Alphabets2.java	Looping over characters.
+if-else	electricityBill.java	Conditional logic & user input.
+Inheritance	Account.java, Bank.java	Class hierarchy, inheritance, overriding.
+switch_case	D_M_Y_Converter.java	Switch‑case with dates and enums.
+PYQ/TNTYFIV	Colsum.java	2‑D arrays, column sums, I/O.
+Perni.java	Recursion & binary number validation.
+Feel free to open any file, modify it, recompile, and see the result instantly.
+
+🚀 Quick Demo: Colsum
+Potentially dangerous command
+Bash
+Run
+$ cd PYQ/TNTYFIV
+$ javac Colsum.java
+$ java Colsum
+Enter 12 integers (row-major order):
+1 2 3 4
+5 6 7 8
+9 10 11 12
+Column sums:
+col 1: 15
+col 2: 18
+col 3: 21
+col 4: 24
+📜 License
+This repository is released under the MIT license – feel free to copy, modify and use the code for learning or production purposes.
\ No newline at end of file

From c136ac4d7c4a80e076e2b75a0d612009a0765f12 Mon Sep 17 00:00:00 2001
From: pandariptor <SinfulBobcat>
Date: Thu, 19 Mar 2026 18:46:21 +0530
Subject: [PATCH 2/4] stuff

---
 .vscode/settings.json       |  3 +-
 .zed/debug.json             |  0
 FinalRevision/Colsum.java   | 88 +++++++++++++++++++++++++++++++++++++
 FinalRevision/Flipgram.java | 55 +++++++++++++++++++++++
 FinalRevision/Perni.java    | 46 +++++++++++++++++++
 FinalRevision/Rearrage.java | 37 ++++++++++++++++
 TODO                        |  5 ++-
 7 files changed, 232 insertions(+), 2 deletions(-)
 create mode 100644 .zed/debug.json
 create mode 100644 FinalRevision/Colsum.java
 create mode 100644 FinalRevision/Flipgram.java
 create mode 100644 FinalRevision/Perni.java
 create mode 100644 FinalRevision/Rearrage.java

diff --git a/.vscode/settings.json b/.vscode/settings.json
index f3b5b9c..6ddfdda 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -4,7 +4,8 @@
         "if-else",
         "for_loop",
         "Class12Project",
-        "Inheritance"
+        "Inheritance",
+        "FinalRevision"
     ],
     "java.project.outputPath": "bin",
     "java.project.referencedLibraries": [
diff --git a/.zed/debug.json b/.zed/debug.json
new file mode 100644
index 0000000..e69de29
diff --git a/FinalRevision/Colsum.java b/FinalRevision/Colsum.java
new file mode 100644
index 0000000..98562fc
--- /dev/null
+++ b/FinalRevision/Colsum.java
@@ -0,0 +1,88 @@
+
+import java.util.Scanner;
+
+public class Colsum {
+
+    int mat[][], m, n;
+
+    public Colsum(int mm, int nn) {
+        m = mm;
+        n = nn;
+
+    }
+
+    void readArray()
+    {
+        mat = new int[m][n];
+        Scanner x = new Scanner(System.in);
+        System.out.println("Enter array elements for MATRIX "+((int)(100*Math.random())));
+        for(int i=0; i<m; i++)
+        {
+            for(int j=0;j<n;j++)
+            {
+                mat[i][j] = x.nextInt();
+            }
+        }
+
+        x.close();
+    }
+
+    boolean check (Colsum A, Colsum B)
+    {
+        int sum1 = 0;
+        int sum2 = 0;
+        for(int i=0; i<n; i++)
+        {
+            sum1=0;
+            sum2=0;
+
+            for(int j=0; j<m; j++)
+            {
+                sum1 += A.mat[j][i];
+                sum2 += B.mat[j][i];
+            }
+
+            if (sum1==sum2) continue;
+            else return false;
+        }
+        
+
+        return true;
+    }
+
+    void print()
+    {
+        // FIRST
+        System.out.println("---------- MATRIX "+(int)(100*Math.random())+"----------");
+        for(int i=0;i<m;i++)
+        {
+            for(int j=0;j<m;j++)
+            {
+                System.out.print(mat[i][j] + "  ");
+            }
+            System.out.println();
+        }
+    }
+
+    
+    public static void main(String[] args) {
+        Scanner x = new Scanner(System.in);
+        System.out.println("Enter the rows and column for ");
+        int in=x.nextInt();
+        int im=x.nextInt();
+
+        Colsum C1 = new Colsum(in, im);
+        Colsum C2 = new Colsum(in, im);
+
+        C1.readArray();
+        C2.readArray();
+
+        System.out.println("========================Array print========================");
+        C1.print();
+        C2.print();
+
+        C1.check(C1,C2);
+
+        x.close();
+    }
+}
diff --git a/FinalRevision/Flipgram.java b/FinalRevision/Flipgram.java
new file mode 100644
index 0000000..e8f3479
--- /dev/null
+++ b/FinalRevision/Flipgram.java
@@ -0,0 +1,55 @@
+import java.util.Scanner;
+
+public class Flipgram {
+    String word;
+
+    public Flipgram(String s) {
+        word = s;
+    }
+
+    boolean isHetero()
+    {
+        String lwrCase = word.toLowerCase();
+        for(int i=0;i<lwrCase.length(); i++)
+        {
+            char currentChar = lwrCase.charAt(i);
+            if(lwrCase.indexOf(currentChar, i+1)!=-1) return false;
+        }
+        return true;
+    }
+
+    String flip()
+    {
+        int len = word.length();
+        int mid = len/2;
+        char midl = word.charAt(mid);
+        String flipa;
+
+        if(len%2==0)
+            flipa = word.substring(mid)+word.substring(0,mid);
+        else
+             flipa = word.substring(mid+1)+midl+word.substring(0,mid);
+        return flipa;
+    }
+
+    void display()
+    {
+        if(!isHetero())
+        {
+            System.out.println(flip().toUpperCase());
+        }
+        else{
+            System.out.println("HETEROGRAM");
+        }
+    }
+
+    public static void main(String[] args) {
+        Scanner x = new Scanner(System.in);
+        String sc = x.next();
+
+        Flipgram obj = new Flipgram(sc);
+        obj.display();
+        x.close();
+    }
+    
+}
diff --git a/FinalRevision/Perni.java b/FinalRevision/Perni.java
new file mode 100644
index 0000000..64f83d0
--- /dev/null
+++ b/FinalRevision/Perni.java
@@ -0,0 +1,46 @@
+import java.util.Scanner;
+
+class Perni {
+
+    public static void main(String[] args) {
+        Scanner x = new Scanner(System.in);
+        int in_in = x.nextInt();
+        x.close();
+        int in = in_in;
+        int inin = in_in;
+        int s = 0;
+        boolean p = false;
+        int len = 0;
+        while (in != 0) {
+            int d = in % 10;
+            s += d;
+            in /= 10;
+        }
+        for (int i = 1; i <= (int) Math.sqrt(s); i++) {
+            if (s % i == 0) {
+                System.out.println();
+                len++;
+            }
+            
+        }
+        if (len>1) System.out.println("not prime");
+        else 
+        {
+            System.out.println("prime");
+            p = true;
+        }
+        len=0;
+        if (p) {
+            while (inin != 0) {
+                int d = inin % 10;
+                len++;
+                inin/=10;
+                if (d != 0 && d != 1) System.exit(0);
+            }
+            if (len < 2) System.exit(0);
+            System.out.println("YEAHHHHH!");
+        } else {
+            System.out.println("NAWWWWWH!");
+        }
+    }
+}
diff --git a/FinalRevision/Rearrage.java b/FinalRevision/Rearrage.java
new file mode 100644
index 0000000..e1561f3
--- /dev/null
+++ b/FinalRevision/Rearrage.java
@@ -0,0 +1,37 @@
+import java.util.Scanner;
+
+class Rearrange
+{
+    String wrd, newwrd;
+    
+    
+    Rearrange()
+    {
+        wrd="";
+        newwrd=""; 
+    }
+
+
+    void readword()
+    {
+        Scanner x = new Scanner(System.in);
+        System.out.println("Enter a word");
+        wrd = x.next();
+        wrd = wrd.toUpperCase();
+        
+    }
+
+    void freq_vow()
+    {
+        int f1=0;
+        int f2=0;
+        for(int i=0; i<wrd.length(); i++)
+        {
+            if ("aeiou".indexOf(wrd.charAt(i)) == -1)
+                f1+=1;
+            else
+                f2+=1;
+        }
+    }
+
+}
\ No newline at end of file
diff --git a/TODO b/TODO
index f47005c..8627e9a 100644
--- a/TODO
+++ b/TODO
@@ -1,3 +1,6 @@
 
 Todo:
-  ☐ die
+  [x] die
+
+
+based on your experience with macos and apple stuff, do u recommend me getting a macbook neo for my college stuff
\ No newline at end of file

From d84d56c90e560a0bae4728b4268bd780a47d4bd2 Mon Sep 17 00:00:00 2001
From: pandariptor <SinfulBobcat>
Date: Mon, 23 Mar 2026 22:12:19 +0530
Subject: [PATCH 3/4] trialDryRun

---
 FinalRevision/TestLoopOutput.java | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
 create mode 100644 FinalRevision/TestLoopOutput.java

diff --git a/FinalRevision/TestLoopOutput.java b/FinalRevision/TestLoopOutput.java
new file mode 100644
index 0000000..3b4c01d
--- /dev/null
+++ b/FinalRevision/TestLoopOutput.java
@@ -0,0 +1,19 @@
+public class TestLoopOutput {
+    
+    static void test(int count)
+    {
+        if (count==0)
+        {
+            System.out.println(" ");
+        }
+        else
+        {
+            System.out.println("Bye"+count);
+            test(--count);
+            System.out.println(" "+count);
+        }
+    }
+    public static void main(String[] args) {
+        test(4);
+    }
+}

From 95214b566981c6097817b32e62eb8551a7007d7e Mon Sep 17 00:00:00 2001
From: pandariptor <SinfulBobcat>
Date: Wed, 25 Mar 2026 18:09:11 +0530
Subject: [PATCH 4/4] a lot of new stuff

---
 .vscode/settings.json                       |   3 +-
 FinalRevision/Colors.java                   |  12 +
 FinalRevision/{Colsum.java => Colsum2.java} |  10 +-
 FinalRevision/MatRev.java                   |  22 ++
 FinalRevision/{Perni.java => Perni2.java}   |   2 +-
 FinalRevision/Recursion.java                | 237 ++++++++++++++++++++
 PYQ/TNTYFIV/Colsum.java                     |   5 +-
 RUN_ME.java                                 |  79 +++++++
 bin/.gitattributes                          |   2 +
 bin/.gitignore                              |  24 ++
 bin/.vscode/settings.json                   |  15 ++
 bin/.zed/debug.json                         |   0
 bin/README.md                               |  69 ++++++
 bin/TODO                                    |   6 +
 14 files changed, 478 insertions(+), 8 deletions(-)
 create mode 100644 FinalRevision/Colors.java
 rename FinalRevision/{Colsum.java => Colsum2.java} (89%)
 create mode 100644 FinalRevision/MatRev.java
 rename FinalRevision/{Perni.java => Perni2.java} (98%)
 create mode 100644 FinalRevision/Recursion.java
 create mode 100644 RUN_ME.java
 create mode 100644 bin/.gitattributes
 create mode 100644 bin/.gitignore
 create mode 100644 bin/.vscode/settings.json
 create mode 100644 bin/.zed/debug.json
 create mode 100644 bin/README.md
 create mode 100644 bin/TODO

diff --git a/.vscode/settings.json b/.vscode/settings.json
index 6ddfdda..f41bb2a 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -5,7 +5,8 @@
         "for_loop",
         "Class12Project",
         "Inheritance",
-        "FinalRevision"
+        "FinalRevision",
+        ""
     ],
     "java.project.outputPath": "bin",
     "java.project.referencedLibraries": [
diff --git a/FinalRevision/Colors.java b/FinalRevision/Colors.java
new file mode 100644
index 0000000..7aff448
--- /dev/null
+++ b/FinalRevision/Colors.java
@@ -0,0 +1,12 @@
+public class Colors {
+    public static final String RESET = "\u001B[0m";
+
+    public static final String RED = "\u001B[31m";
+    public static final String GREEN = "\u001B[32m";
+    public static final String YELLOW = "\u001B[33m";
+    public static final String BLUE = "\u001B[34m";
+    public static final String PURPLE = "\u001B[35m";
+    public static final String CYAN = "\u001B[36m";
+
+    public static final String BOLD = "\u001B[1m";
+}
\ No newline at end of file
diff --git a/FinalRevision/Colsum.java b/FinalRevision/Colsum2.java
similarity index 89%
rename from FinalRevision/Colsum.java
rename to FinalRevision/Colsum2.java
index 98562fc..16fd694 100644
--- a/FinalRevision/Colsum.java
+++ b/FinalRevision/Colsum2.java
@@ -1,11 +1,11 @@
 
 import java.util.Scanner;
 
-public class Colsum {
+public class Colsum2 {
 
     int mat[][], m, n;
 
-    public Colsum(int mm, int nn) {
+    public Colsum2(int mm, int nn) {
         m = mm;
         n = nn;
 
@@ -27,7 +27,7 @@ void readArray()
         x.close();
     }
 
-    boolean check (Colsum A, Colsum B)
+    boolean check (Colsum2 A, Colsum2 B)
     {
         int sum1 = 0;
         int sum2 = 0;
@@ -71,8 +71,8 @@ public static void main(String[] args) {
         int in=x.nextInt();
         int im=x.nextInt();
 
-        Colsum C1 = new Colsum(in, im);
-        Colsum C2 = new Colsum(in, im);
+        Colsum2 C1 = new Colsum2(in, im);
+        Colsum2 C2 = new Colsum2(in, im);
 
         C1.readArray();
         C2.readArray();
diff --git a/FinalRevision/MatRev.java b/FinalRevision/MatRev.java
new file mode 100644
index 0000000..c034cca
--- /dev/null
+++ b/FinalRevision/MatRev.java
@@ -0,0 +1,22 @@
+import java.util.Scanner;
+
+public class MatRev {
+    int arr[][], m, n;
+
+    MatRev(int mm, int nn)
+    {
+        m = mm;
+        n = nn;
+    }
+
+    void fillarray()
+    {
+        Scanner x = new Scanner(System.in);
+        for (int i = 0; i < m; i++) {
+            for (int j = 0; j < n; j++) {
+                System.out.println("Enter the array element "+i+","+j+": ");
+                arr[i][j] = x.nextInt();
+            }
+        }
+    }
+}
diff --git a/FinalRevision/Perni.java b/FinalRevision/Perni2.java
similarity index 98%
rename from FinalRevision/Perni.java
rename to FinalRevision/Perni2.java
index 64f83d0..ff7859b 100644
--- a/FinalRevision/Perni.java
+++ b/FinalRevision/Perni2.java
@@ -1,6 +1,6 @@
 import java.util.Scanner;
 
-class Perni {
+class Perni2 {
 
     public static void main(String[] args) {
         Scanner x = new Scanner(System.in);
diff --git a/FinalRevision/Recursion.java b/FinalRevision/Recursion.java
new file mode 100644
index 0000000..869dd0d
--- /dev/null
+++ b/FinalRevision/Recursion.java
@@ -0,0 +1,237 @@
+import java.nio.channels.Pipe.SourceChannel;
+import java.util.Scanner;
+
+public class Recursion {
+
+
+    static final char [] DIGITS = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F',
+     'G', 'H', 'I', 'J' , 'K', 'L', 'M', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};
+
+    final int MAX_BASE = 36;
+    static int t = 0;
+    static int a,b,c,limit;
+    
+    public static void main(String[] args) {
+        Scanner x = new Scanner(System.in);
+        int ch;
+        printMenu();
+        ch = x.nextInt();
+        switch (ch) {
+            case 0:
+            System.out.println("Exiting...");
+            System.exit(0);
+            break;
+            
+            
+            case 1:
+            System.out.print(Colors.BLUE);
+            System.out.println("Input the base");
+            int m = x.nextInt();
+            System.out.println("Input the exponent");
+            int n = x.nextInt();
+            System.out.print(Colors.RESET);
+            System.out.print(Colors.GREEN);
+            System.out.println(power(m, n));
+            break;
+            
+            
+            case 2:
+            System.out.print(Colors.BLUE);
+            System.out.println("Enter the limit");
+            int l = x.nextInt();
+            System.out.print(Colors.RESET);
+            System.out.print(Colors.GREEN);
+            System.out.println(sum(l));
+            break;
+            case 3:
+            System.out.print(Colors.BLUE);
+            System.out.println("Enter the two numbers");
+            int n1 = x.nextInt();
+            int n2 = x.nextInt();
+            System.out.print(Colors.RESET);
+            System.out.print(Colors.GREEN);
+            System.out.println(hcf(n1, n2));
+            break;
+            case 4:
+            System.out.println(Colors.BLUE+"Enter the number");
+            System.out.print(Colors.RESET);
+            int n3 = x.nextInt();
+            System.out.println(Colors.GREEN + factorial(n3));
+            break;
+
+            case 5:
+            System.out.println("this shit broken");
+            //int lm = x.nextInt();
+            // System.out.println(fibbonacci(lm));
+            break;
+
+            case 6:
+                System.out.println(Colors.BLUE + "Enter the number of elements in the array");
+                int ar_lim = x.nextInt();
+                int arr[] = new int[ar_lim];
+                System.out.println(Colors.BOLD + "-=-=-=-=-==-=-=-=   ARRAY INPUT   =-=-=-=-=-=-=-=-=-=-");
+                System.out.print(Colors.RESET+Colors.PURPLE);
+                for(int i = 0; i<ar_lim; i++)
+                {
+                    System.out.print("Enter array element for position number "+(i+1)+": ");
+                    arr[i] = x.nextInt();
+                }
+                sort(arr, ar_lim);
+                for(int i = 0; i<ar_lim; i++)
+                {
+                    System.out.print(arr[i]+",");
+                }
+                System.out.println(Colors.YELLOW+"Enter the search element");
+                int ele = x.nextInt();
+
+                if(binSearch(arr, ele, ar_lim-1, 0)!=-1) System.out.println(Colors.GREEN+Colors.BOLD+"    FOUND !!!!!");
+                else
+                    System.out.println(Colors.RED+Colors.BOLD+" NOT FOUND !!!!!!!");
+
+
+            
+            break;
+
+            case 7:
+                System.out.println(Colors.BOLD+Colors.BLUE+"Enter the number");
+                int num = x.nextInt();
+                System.out.println(Colors.YELLOW+"Enter the base to which you want to convert this number into");
+                int base = x.nextInt();
+
+                base = (base<0)?-base:base;
+
+                printBase(num, base);
+            
+            break;
+
+            case 8:
+                System.out.print("Enter a number to reverse");
+                int n5 = x.nextInt();
+                System.out.println(printReverse(n5));
+                break;
+            
+                case 9:
+                    System.out.println("Enter number");
+                    int n6 = x.nextInt();
+                    int sum = armstrongSum(n6);
+                    if(sum==n6) System.out.println("YAY");
+                    else System.out.println("NAY");
+                    break;
+            default:
+            System.out.println("Wrong Input!");
+            break;
+        }
+    }
+    public static void printMenu() {
+        System.out.print(Colors.CYAN);
+        System.out.println("\n====================================");
+        System.out.println("               RECURSION              ");
+        System.out.println("====================================");
+        System.out.println(" 1. Power m^n");
+        System.out.println(" 2. Sum upto n");
+        System.out.println(" 3. HCF m,n");
+        System.out.println(" 4. Factorial n");
+        System.out.println(" 5. Fibonacci n  -- broken ");
+        System.out.println(" 6. Binary Search n");
+        System.out.println(" 7. Decimal to Binary");
+        System.out.println(" 8. Reverse number\n 9. Armstrong");
+        System.out.println(" 0. Exit");
+
+        System.out.println("====================================");
+        System.out.println(Colors.RESET);
+    }
+    
+    static int power(int m, int n)
+    {
+        if (n==0) return 1;
+        return (m*power(m, n-1));
+        
+    }
+    
+    static int sum(int n)
+    {
+        if (n==0) return 0;
+        return (++t+sum(n-1));
+    }
+    
+    static int hcf(int p, int q)
+    {
+        if (q==0) return p;
+        return hcf(q, p%q);
+    }
+    
+    static int factorial(int n)
+    {
+        if(n<2) return 1;
+        return n*factorial(n-1);
+    }
+    
+    // static void printFibonacciSeries(int terms)
+    // {
+    //     for (int i = 0; i < terms; i++)
+    //         {
+    //         System.out.print(fibonacci(i) + " ");
+    //     }
+    //     System.out.println();
+    // }
+    static int[] sort(int []a, int n)
+    {
+        int t;
+        for(int i=0; i<n-1; i++)
+        {
+            for(int j=0; j<n-i-1; j++)
+            {
+                if(a[j]>a[j+1])
+                {
+                    t = a[j];
+                    a[j] = a[j+1];
+                    a[j+1] = t;
+                }
+            }
+        }
+        return a;
+    }
+    static int binSearch(int [] a, int x, int high, int low)
+    {
+        if(low>high) return -1;
+        int mid = (low+high)/2;
+
+        if       (a[mid] > x)
+            return binSearch(a,x,mid-1,low);
+        else if  (a[mid] < x)
+            return binSearch(a, x, high, mid+1);
+        else
+            return 67;
+    }
+
+
+    /**
+     * HARDEST SHIT EVER IG (NOT REALLY)
+     * CONVERTING ANY BASE TO ANY BASE?
+     * WHY? COZ I SAID SO
+    */
+
+    static void printBase(int num, int base)
+    {
+        if (num >= base) printBase(num/base, base); 
+        System.out.print(Colors.GREEN+""+DIGITS[num%base]);
+    }
+
+    static int printReverse(int n)
+    {
+        if(n<10) return n;
+        else{
+            int d = n%10;
+            return (d*10+printReverse(n/10));
+        }
+    }
+
+    static int armstrongSum(int n)
+    {
+        if(n<10) return n*n*n;
+        int d = n%10;
+        return (d*d*d + armstrongSum(n/10));
+    }
+
+}
+
diff --git a/PYQ/TNTYFIV/Colsum.java b/PYQ/TNTYFIV/Colsum.java
index 7618007..5482b69 100644
--- a/PYQ/TNTYFIV/Colsum.java
+++ b/PYQ/TNTYFIV/Colsum.java
@@ -1,3 +1,5 @@
+import java.util.Scanner;
+
 public class Colsum {
     int mat[][] , m , n;
     Colsum(int mm, int nn)
@@ -8,11 +10,12 @@ public class Colsum {
     }
     void readArray()
     {
+        Scanner x = new Scanner(System.in);
         for (int i = 0; i <= m; i++)
         {
             for (int j = 0; j <= n; j++) {
                 System.out.print("Enter element for "+i+"th row and "+j+"th column:");
-                mat[i][j] = x.nextInt;
+                mat[i][j] = x.nextInt();
                 
                 
             }    
diff --git a/RUN_ME.java b/RUN_ME.java
new file mode 100644
index 0000000..151331e
--- /dev/null
+++ b/RUN_ME.java
@@ -0,0 +1,79 @@
+import java.io.File;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Scanner;
+
+public class RUN_ME {
+
+    static List<String> classList = new ArrayList<>();
+
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+
+        // Step 1: Scan bin directory
+        File binDir = new File("bin");
+        if (!binDir.exists()) {
+            System.out.println("bin directory not found.");
+            return;
+        }
+
+        scanClasses(binDir, "");
+
+        if (classList.size() == 0) {
+            System.out.println("No compiled classes found.");
+            return;
+        }
+
+        // Step 2: Display menu
+        while (true) {
+            System.out.println("\n===== PROGRAM LAUNCHER =====");
+            for (int i = 0; i < classList.size(); i++) {
+                System.out.println((i + 1) + ". " + classList.get(i));
+            }
+            System.out.println("0. Exit");
+
+            System.out.print("Enter choice: ");
+            int choice = sc.nextInt();
+
+            if (choice == 0) {
+                System.out.println("Exiting...");
+                break;
+            }
+
+            if (choice < 1 || choice > classList.size()) {
+                System.out.println("Invalid choice.");
+                continue;
+            }
+
+            String className = classList.get(choice - 1);
+
+            // Step 3: Run selected class
+            try {
+                System.out.println("\n--- Running: " + className + " ---\n");
+
+                Class<?> cls = Class.forName(className);
+                cls.getMethod("main", String[].class)
+                   .invoke(null, (Object) new String[]{});
+
+            } catch (Exception e) {
+                System.out.println("Error running class: " + className);
+                e.printStackTrace();
+            }
+        }
+
+        sc.close();
+    }
+
+    // Recursive scanner
+    static void scanClasses(File dir, String packageName) {
+        for (File file : dir.listFiles()) {
+            if (file.isDirectory()) {
+                scanClasses(file, packageName + file.getName() + ".");
+            } else if (file.getName().endsWith(".class")) {
+                String className = packageName +
+                        file.getName().replace(".class", "");
+                classList.add(className);
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/bin/.gitattributes b/bin/.gitattributes
new file mode 100644
index 0000000..dfe0770
--- /dev/null
+++ b/bin/.gitattributes
@@ -0,0 +1,2 @@
+# Auto detect text files and perform LF normalization
+* text=auto
diff --git a/bin/.gitignore b/bin/.gitignore
new file mode 100644
index 0000000..524f096
--- /dev/null
+++ b/bin/.gitignore
@@ -0,0 +1,24 @@
+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+replay_pid*
diff --git a/bin/.vscode/settings.json b/bin/.vscode/settings.json
new file mode 100644
index 0000000..f41bb2a
--- /dev/null
+++ b/bin/.vscode/settings.json
@@ -0,0 +1,15 @@
+{
+    "java.project.sourcePaths": [
+        "switch_case",
+        "if-else",
+        "for_loop",
+        "Class12Project",
+        "Inheritance",
+        "FinalRevision",
+        ""
+    ],
+    "java.project.outputPath": "bin",
+    "java.project.referencedLibraries": [
+        "lib/**/*.jar"
+    ]
+}
diff --git a/bin/.zed/debug.json b/bin/.zed/debug.json
new file mode 100644
index 0000000..e69de29
diff --git a/bin/README.md b/bin/README.md
new file mode 100644
index 0000000..6a77a8d
--- /dev/null
+++ b/bin/README.md
@@ -0,0 +1,69 @@
+# 📚 Java Practice Collection
+A growing library of small Java programs that illustrate core language concepts – loops, conditionals, arrays, classes, inheritance, I/O, and more.
+
+Why this repo?
+• 100+ self‑contained examples written while learning Java (2018‑2023).
+• Ready to copy‑paste, compile, run, or import into any IDE.
+• All files are plain .java – no external dependencies or build tools required.
+
+📁 Folder Overview
+Folder	Typical Contents / Purpose
+bin/	Compiled .class files (generated automatically by javac). No source code lives here.
+Class12Project/	Exercises from a 12th‑grade curriculum (e.g., simple programs, loops, conditionals).
+for_loop/	Programs that demonstrate for, while, and do‑while loops – e.g., alphabet printing, array iteration.
+if-else/	Examples of conditional logic (if/else, switch) plus small utility programs (electricity bill calculator, date converter).
+Inheritance/	Basic class hierarchies that show inheritance, method overriding, and simple object models (Account, Bank, etc.).
+PYQ/TNTYFIV/	Practice questions from programming contests. Contains the Colsum column‑sum calculator and the Perni binary‑number checker.
+switch_case/	Programs that heavily use Java’s switch statement (date converters, menu systems, etc.).
+Tip: All source files are plain Java (.java). No external dependencies or build tools required.
+
+⚙️ How to Compile & Run
+The following one‑liner compiles every .java file in the repository and places the resulting .class files alongside their sources:
+
+Potentially dangerous command
+Bash
+Run
+find . -name "*.java" | xargs javac
+After compilation, run any program by specifying its fully‑qualified class name (the directory path is used as the package prefix because no explicit package statements are present):
+
+Potentially dangerous command
+Bash
+Run
+### Example: run Colsum
+cd PYQ/TNTYFIV
+java Colsum
+
+### Run a for‑loop example
+java for_loop.Alphabets2
+Why this stays future‑proof
+• Adding new .java files automatically picks them up – no manual edits.
+• The run command never changes because it relies only on the file name, not an explicit list.
+
+📖 Program Highlights
+Folder	Example	What it teaches
+for_loop	Alphabets2.java	Looping over characters.
+if-else	electricityBill.java	Conditional logic & user input.
+Inheritance	Account.java, Bank.java	Class hierarchy, inheritance, overriding.
+switch_case	D_M_Y_Converter.java	Switch‑case with dates and enums.
+PYQ/TNTYFIV	Colsum.java	2‑D arrays, column sums, I/O.
+Perni.java	Recursion & binary number validation.
+Feel free to open any file, modify it, recompile, and see the result instantly.
+
+🚀 Quick Demo: Colsum
+Potentially dangerous command
+Bash
+Run
+$ cd PYQ/TNTYFIV
+$ javac Colsum.java
+$ java Colsum
+Enter 12 integers (row-major order):
+1 2 3 4
+5 6 7 8
+9 10 11 12
+Column sums:
+col 1: 15
+col 2: 18
+col 3: 21
+col 4: 24
+📜 License
+This repository is released under the MIT license – feel free to copy, modify and use the code for learning or production purposes.
\ No newline at end of file
diff --git a/bin/TODO b/bin/TODO
new file mode 100644
index 0000000..8627e9a
--- /dev/null
+++ b/bin/TODO
@@ -0,0 +1,6 @@
+
+Todo:
+  [x] die
+
+
+based on your experience with macos and apple stuff, do u recommend me getting a macbook neo for my college stuff
\ No newline at end of file