• Program:

public class Main {

  public static void main(String[] args) {

    int count = 0, number = 0003452;

    while (number != 0) {
      // number = number/10
      number /= 10;
      ++count;
    }

    System.out.println("Number of digits: " + count);
  }
}

• Output:

Number of digits: 4

• Program:

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

    char n;

    for(n = 'A'; n <= 'Z'; ++n) // For lowercase: for(n = 'a'; n <= 'b'; ++n)
      System.out.print(n + " ");
    }
}

• Output:

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 

• Program:

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

        int a = 72, b = 120, lcm;

        // maximum number between a and b is stored in lcm
        lcm = (a > b) ? a : b;
        while(true) {
            if( lcm % a == 0 && lcm % b == 0 ) {
                System.out.printf("The LCM of %d and %d is %d.", a, b, lcm);
                break;
            }
            ++lcm;
        }
    }
}

• Output:

The LCM of 72 and 120 is 360.

• Program:

class Main {
  public static void main(String[] args) {
    
    int n1 = 11, n2 = 102; // find GCD between n1 and n2
   
    int gcd = 1; // initially set to gcd

    for (int i = 1; i <= n1 && i <= n2; ++i) {
   
      if (n1 % i == 0 && n2 % i == 0) // check if i perfectly divides both n1 and n2
        gcd = i;
    }

    System.out.println("GCD of " + n1 +" and " + n2 + " is " + gcd);
  }
}

• Output:

GCD of 11 and 102 is 1