Module 3: Loop Programs
Java programs that practice loops (for, while, do-while) and iterative logic.
25 program solutions
Program Solutions
Print 1–100
Print numbers from 1 to 100 using a loop.
Print Even Numbers
Print all even numbers in a given range.
Print Odd Numbers
Print all odd numbers in a given range.
Factorial
Find factorial of a number using a loop.
Reverse a Number
Reverse the digits of a number using a loop.
Sum of Digits
Compute the sum of digits of a number.
Count Digits
Count the number of digits in a given integer.
Armstrong Numbers in Range
Print all Armstrong numbers in a given range.
Prime Numbers in Range
Print all prime numbers in a given range.
Fibonacci Series
Print Fibonacci series up to N terms using a loop.
GCD (HCF)
Find the greatest common divisor (HCF) of two numbers using Euclidean algorithm.
LCM
Find the least common multiple of two numbers using GCD.
Power of Number
Compute a^b using a loop (similar to earlier power program).
Sum of Series
Compute the sum of the series 1 + 2 + ... + n using a loop.
Number Patterns
Print a simple increasing number triangle pattern.
Star Patterns
Print a simple right-angled triangle star pattern.
Floyd Triangle
Print Floyd’s triangle pattern using consecutive numbers.
Pascal Triangle
Generate Pascal’s triangle using loops and binomial coefficients.
Multiplication Table
Print the multiplication table of a given number.
Factor Pairs
Print all factor pairs (i, n/i) of a given number.
Prime Check
Check whether a given number is prime using a loop.
Composite Check
Check whether a given number is composite.
Perfect Square Check
Check whether a number is a perfect square using loops.
Harshad Number
Check whether a number is a Harshad (Niven) number (divisible by sum of its digits).
Duck Number
Check whether a number is a duck number (contains zero, but not at the first position).
Topic Strategy: Module 3: Loop Programs
This topic is best practiced through repetition with variation. Solve each program, then modify constraints and test alternate approaches so you understand why one solution performs better than another.
During interviews, explain the approach before coding: input assumptions, core logic, complexity, and edge cases. Clear reasoning often matters as much as final code correctness.
Once comfortable, time-box each question and target clean, readable code with meaningful variable names and a quick dry run explanation.