Programs using loops in java solved by one of my student.Very useful to crack interviews.

package com.loops;

public class LoopExcercises {

public static void main(String[] args) {
// TODO Auto-generated method stub
for (int i=1;i<=1000;i++) {
int number = i ,temp,rev = 0 ,r=1 ;
temp = number;
while (number != 0) {
r = number%10;
number = number/10;
rev = rev*10 + r;
}

if (rev == temp) {
System.out.println("This is palindrome "+i);
}
}
}
}


class primeNumber1000 {
public static void main(String[] args) {

for (int j=3;j<=1000;j++)
{
int i = 1,count = 0;
int number = j;
while (i<= number) {
if (number%i == 0) {
count++;
}
i++;
}
if(count == 2) {
System.out.println("This is prime number " + number);
}
}
}
}

class armstrongNumber1000 {
public static void main(String[] args) {
for (int i = 1; i < 1000; i++) {
int number = i,remainder = 1, sum = 0;
int temp = number;
while (number != 0) {
remainder = number%10;
number = number/10;
sum += remainder*remainder*remainder;
}
if (temp == sum) {
System.out.println("The armstrong number is: "+temp);
}

}
}
}

class armstrongNumberSum {
public static void main(String[] args) {
int totalSum = 0;
for (int i = 1; i < 1000; i++) {
int number = i,remainder = 1, sum = 0;
int temp = number;
while (number != 0) {
remainder = number%10;
number = number/10;
sum += remainder*remainder*remainder;
}
if (temp == sum) {
System.out.println("The armstrong number is: "+temp);
totalSum += temp;
System.out.println("The total armstrong number sum is: "+totalSum);
}

}
}
}

class PrimeArmstrong {
public static void main(String[] args) {
for (int i = 1; i < 1000; i++) {
int number = i,remainder = 1, sum = 0,j=1, count = 0;
int temp = number;
while (number != 0) {
remainder = number%10;
number = number/10;
sum += remainder*remainder*remainder;
}
if (temp == sum) {
System.out.println("The armstrong number is: "+temp);
while (j <= temp) {
if ( temp%j == 0) {
count++;
}
j++;
}
if(count == 2) {
System.out.println("This is prime armstrong :"+temp);
}
}

}
}
}


class palindromeSum {
public static void main(String[] args) {
int totalSum = 0;
for (int i=1;i<=1000;i++) {
int number = i ,temp,rev = 0 ,r=1 ;
temp = number;
while (number != 0) {
r = number%10;
number = number/10;
rev = rev*10 + r;
}

if (rev == temp) {
System.out.println("This is palindrome "+i);
totalSum += temp;
System.out.println("The total Sum of Palindromes upto 100: "+totalSum);
}
}
}
}

class PalindromePrime{
public static void main(String[] args) {
for (int i=1;i<=1000;i++) {
int number = i ,temp,rev = 0 ,r=1, j=1, count =0 ;
temp = number;
while (number != 0) {
r = number%10;
number = number/10;
rev = rev*10 + r;
}

if (rev == temp) {
// System.out.println("This is palindrome "+i);
while(j<= temp) {
if(temp%j == 0) {
count++;
}
j++;
}
if (count == 2) {
System.out.println("This is a prime palindrome: "+temp);
}
}
}
}
}

class PrimeSum {
public static void main(String[] args) {
int totalSum = 2;
for (int j=3;j<=1000;j++)
{
int i = 1,count = 0;
int number = j;
while (i<= number) {
if (number%i == 0) {
count++;
}
i++;
}
if(count == 2) {
System.out.println("This is prime number " + number);
totalSum += number;
System.out.println("The total sum of primes upto 1000: "+totalSum);
}
}
}
}


class PerfectPrime {
public static void main(String[] args) {
for (int j=3;j<=1000;j++)
{
int i = 1,count = 0, div = 1, perfectPrime, factorSum = 0;
int number = j;
while (i<= number) {
if (number%i == 0) {
count++;
}
i++;
}
if(count == 2) {
System.out.println("This is prime number " + number);
perfectPrime = number;
while (div < perfectPrime) {
if(perfectPrime%div == 0) {
factorSum += div;
}
div++;
}
if( factorSum == number) {
System.out.println("This is perfect prime number");
}
}
}
}
}



class PrintEvenOddDigits{
public static void main(String[] args) {
int number = 32458, rem = 1;
while (number != 0) {
rem = number%10;
number = number/10;
if (rem%2 == 0) {
System.out.println("Thi is even number of the digit: "+rem);
} else {
System.out.println("This is odd number of the digit: "+rem);
}
}
}
}

class PrintPrimeDigits {
public static void main(String[] args) {
int number = 54671, rem = 1,i=1, count = 0;
while (number != 0) {
rem = number%10;
number  = number/10;
if (rem != 0) {
while (i<= rem) {
if(rem%i == 0) {
count++;
}
i++;
if(count == 2) {
System.out.println("This is prime number of the digit :"+rem);
}
}
}
if( number < 10 && number != 0) {
while (i <= number) {
if(number%i == 0) {
count++;
}
i++;
}
if(count == 2) {
System.out.println("This is prime number of the digit :"+number);
}
}
}
}
}


class PrintPerfectDigits {
public static void main(String[] args) {
int num = 12368, rem = 1;
while (num != 0) {
rem = num%10;
num = num/10;

int sum = 0, temp, i=1;
temp = rem;

while (i < temp) {
if(temp%i == 0) {
sum += i;
}
i++;
if(temp == sum) {
System.out.println("This is perfect number of digit: "+temp);
}
}
// i=1; sum=0;
}
}
}

class PrintMiddleDigits{
public static void main(String[] args) {
int num = 34625, rem = 1, count = 0, middleNum = 0, temp = 1;
int rem1 = 1;
while (num != 0) {
rem = num%10;
num = num/10;
count++;
if(count == 1) {
temp = num;
while(temp != 0) {
rem1= temp%10;
temp = temp/10;
// System.out.println(rem1);
middleNum = middleNum*10+rem1;
// System.out.println(middleNum);
}
temp = middleNum/10;
System.out.println(temp);
}

}
}
}