List of Some important problem for java
1. Write a program in Java to check if a number is even or odd in Java? (input 2 output true, input 3 : output false)
A number is called even if it is completely divisible by two and odd if it’s not completely divisible by two. For example number 4 is even number because when you do 4/2 , remainder is 0 which means 4 is completely divisible by 2. On the other hand 5 is odd number because 5/2 will result in remainder as 1.
2. Write a program in Java to find out if a number is prime in Java? (input 7: output true , input 9 : output false)
A number is called prime if it is divisible by either itself or 1. There are many algorithm to find prime numbers e.g. instead of dividing till number, division upto square root of number may be enough. Start from simplest one and than try to solve this problem with couple of different ways.
3. Write Java program to check if a number is palindrome in Java? ( 121 is palindrome, 321 is not)
A number is called a palindrome if number is equal to reverse of number e.g. 121 is palindrome because reverse of 121 is 121 itself. On the other hand 321 is not palindrome because reverse of 321 is 123 which is not equal to 321. See here for solution of checking if a number is palindrome or not in Java.
4. How to find if a number is power of 2 in Java? (1,2, 4 power of 2, 3 is not)
This is another interesting Java programming exercise. This program can be solved using different ways e.g. using arithmetic operator or by using bit shift operator.
5. Write program to sort an integer array without using API methods?
Sorting questions are one of the integral part of programming questions. There are many sorting algorithm out there to sort any array in Java e.g. Bubble sort, Insertion sort, Selection sort or quick sort. Implementing sorting algorithm itself a good programming exercise in Java.
6. Write Java program to check if a number is Armstrong number or not? (input 153 output true, 123 output false)
An Armstrong number of 3 digit is a number for which sum of cube of its digits are equal to number e.g. 371 is an Armstrong number because 3*3*3 + 7*7*7 + 1*1*1 = 371).
7. Write a program in Java to reverse any String without using StringBuffer?
This is another classical Java programming question. You can reverse String in various way in Java but two programming technique is used to do e.g. Iteration and Recursion. Try solving this problem using Iteration by using Java’s arithmetic operator.
8. Write a program in Java to print Fibonacci series up to given number? Write iterative version.
Fibonacci series a popular number series and very popular programming question in Java, in which number is equal to sum of previous two numbers, starting from third. Fibonacci series is also a good recursion exercise and often asked in Interviews as well. Try doing this exercise by using both Iteration e.g. loops .
9. Write a Java program to calculate factorial of an integer number ? Write iterative solution.
Calculating Factorial is also a classic recursion exercise in programming. Since factorial is a recursive function, recursion becomes natural choice to solve this problem. You just need to remember formula for calculating factorial which is for n! its n*(n-1)*…1.
10. Print following structure in Java?
This program is a good exercise for mastering loops e.g. for loop and while loop in Java. By the way you can print any character and use System.out.print() and System.out.println()) in below example input is 5,
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