☕ Java 30‑day learning

SimpleCalc AgeChecker MultiTable PasswordValidator PatternPrinter StudentGradeSystem ArrayBasics ArrayMaxMin ArrayReverse ArraySearch StudentRecordSystem LoopExam extra structure progress

Simple Calculator

SimpleCalc SimpleCalc.java

Addition, subtraction, multiplication, division
Takes two integers from user
Formatted results

Sample:
Enter first number: 12
Enter second number: 4
12 + 4 = 16
12 - 4 = 8
12 * 4 = 48
12 / 4 = 3

javac SimpleCalc.java && java SimpleCalc

Concepts: Scanner, arithmetic, variables

Age Checker

AgeChecker AgeChecker.java

Categorizes: Toddler, Kid, Teenager, Adult
Voting eligibility & years left
if/else if/else logic

Enter your age: 16
You are a Teenager.
Almost an Adult.
2 more years until you can vote!

javac AgeChecker.java && java AgeChecker

Multiplication table

MultiTable MultiTable.java

User input number, prints 1..10 table
Countdown 10 → 1 with "Blast off!"

=== Multiplication Table of 5===
5 x 1 = 5
...
5 x 10 = 50
=== Counting Down === 10 9 ... 1 🚀

javac MultiTable.java && java MultiTable

Password Validator

PasswordValidator PasswordValidator.java

While loop, unlimited attempts, tracks counter
Hardcoded "java2026"

Attempt 1 Enter password: hello
❌ Wrong password!
Attempt 2 Enter password: java2026
✅ Access granted in 2 attempts!

javac PasswordValidator.java && java PasswordValidator

Pattern Printer

PatternPrinter PatternPrinter.java

Right triangle, square, number triangle (nested loops)

Enter rows: 3
Pattern1: * \n* * \n* * *
Pattern2: square
Pattern3: 1 \n1 2 \n1 2 3

javac PatternPrinter.java && java PatternPrinter

Student Grade System

StudentGradeSystem StudentGradeSystem.java

Name, subjects, marks → total, average, grade (A-F), progress bar

Alex Johnson · 3 subjects
Total 255, Avg 85.0 → B
Progress: ████████░░ 85.0%

javac StudentGradeSystem.java && java StudentGradeSystem

Array basics & operations

ArrayBasics ArrayBasics.java

5 numbers → sum & average

10 20 30 40 50 → sum 150, avg 30.0

javac ArrayBasics.java && java ArrayBasics

ArrayMaxMin ArrayMaxMin.java

Finds max & min

5 numbers: 15 8 23 4 42 → max 42, min 4

javac ArrayMaxMin.java && java ArrayMaxMin

ArrayReverse ArrayReverse.java

Reverses array

[10,20,30,40,50] → [50,40,30,20,10]

javac ArrayReverse.java && java ArrayReverse

ArraySearch ArraySearch.java

Linear search

search 30 in [10,25,30,45,50] → found at position 3

javac ArraySearch.java && java ArraySearch

Student Record System

StudentRecordSystem StudentRecordSystem.java

Parallel arrays: names & marks (3 students)
Top student, search by name

Alice 85, Bob 92, Charlie 78
Top: Bob 92
Search "Bob" → Found Bob-92marks

javac StudentRecordSystem.java && java StudentRecordSystem

Loop exam (table challenge)

LoopExam LoopExam.java

Multiplication table (1-10) + thank‑you message

Enter number: 7
7x1=7 ... 7x10=70
Thank you! re‑run for other tables.

javac LoopExam.java && java LoopExam

Additional practice

Java-Learning-Repo/
├── SimpleCalc.java # basic calculator
├── AgeChecker.java # age categories
├── MultiTable.java # multiplication table
├── PasswordValidator.java # while‑loop password
├── PatternPrinter.java # nested loops patterns
├── StudentGradeSystem.java # grade + progress bar
├── ArrayBasics.java # array sum/avg
├── ArrayMaxMin.java # max & min
├── ArrayReverse.java # reverse array
├── ArraySearch.java # linear search
├── StudentRecordSystem.java # parallel arrays
├── LoopExam.java # table challenge
├── thepledge.java # syntax practice
├── gitcheck.java # git concept demo
├── iamback.java # welcome back
└── README.md # docs (you are here)

Learning progress

Day	Program(s)	Concepts learned
1	Repository setup	Git basics, README
2	SimpleCalc	Scanner, arithmetic
3	AgeChecker	if/else if, comparison
4	MultiTable	for loops, formatting
5	PasswordValidator	while, .equals(), counter
6	PatternPrinter	nested loops
7	StudentGradeSystem	multiple concepts
8	Review & test	assessment days 1‑7
9	ArrayBasics	array declaration, traversal
10	ArrayMaxMin	comparison logic
11	ArrayReverse	array manipulation
12	ArraySearch	linear search
13	StudentRecordSystem	parallel arrays, buffer handling
14	LoopExam	for loop challenge
ongoing	thepledge, gitcheck, iamback	syntax, git practice

How to use this repository

git clone https://github.com/mandar999xxx/java1.git
cd java1
javac ProgramName.java
java ProgramName

Each file is self‑contained, with comments explaining key concepts. Experiment, modify, and learn!

Java Learning Repository