Iterative Constructs in Java

Which of the following segment can be omitted in a for loop?

Which of the following loop executes at least once?

Which of the following is an exit-controlled loop?

Which of the following is an invalid loop?

Which of the following statement causes complete termination of the loop?

Which of the following is an empty loop?

Which of the following is not a jump statement in Java?

How many times will the following code print "Java"?

for (int i = 1; i <= 5; i ++);    
{
    System.out.println("Java");
}  

What will be the output of the following code?

public static void main(String args[]) 
{  
    int sum = 0;   
    for (int i = 1; i <= 5; i++)    
    {    
        sum = i;    
    }    
    System.out.println(sum); 
}  

How many times will the following loop execute?

public static void main(String args[])
{
    int sum = 0;
    for (int i = 10; i > 5; i++)
    {
        sum += i;    
    }
    System.out.println(sum);
}

Which of the following for loops will cause the body of the loop to be executed 10 times?

How many times will the following loop execute?

public static void main(String args[])
{
    int i = 1;
    while (i < 10)
        if (i++ % 2 == 0)
            System.out.println(i);
}

The while loop is an exit-controlled loop.
False

To execute a do-while loop, the condition must be true in the beginning.
False

The while part of a do-while statement must be terminated by a semicolon.
True

All types of loops in Java (for, while, and do-while) can be infinite loops.
True

The continue statement terminates the current loop and then continues from the statement immediately following the current loop.
False

The return statement is a jump statement.
True

The for loop may contain multiple initialisations and updates.
True

A loop that never terminates is called an empty loop.
False

The do-while loop executes at least once even if the condition is false.
True

The do-while loop is an exit-controlled loop.
True

An infinite loop can be constructed using a while loop only.
False

The statements that facilitate unconditional transfer of control are called jump statements.
True

What are loop control structures? What are the essential segments of a loop control structure?

How are these statements different from each other?
i. break

ii. continue

iii. System.exit(0)

iv. return

Identify all the errors in the following statements.

for (int i = 5; i > 0; i++)
{
    System.out.println("Java is fun!");
}

Identify all the errors in the following statements.

while (x < 1 && x > 50)
{
    a = b;
}

Identify all the errors in the following statements.

while (x ==	y)
{
    xx = yy;
    x = y;
}

What is an empty statement? Explain its usefulness.

Convert the following for loop statement into the corresponding while loop and do-while loop:

int sum = 0;
for (int i = 0; i <= 50; i++)
    sum = sum + i;

What are the differences between while loop and do-while loop?

How many times are the following loop bodies repeated? What is the final output in each case?

int x = 2;
while (x < 20)
    if (x % 2 == 0)
        System.out.println(x);

How many times are the following loop bodies repeated? What is the final output in each case?

int y = 2;
while (y < 20)
    if (y % 2 == 0) 
        System.out.println(y++);

How many times are the following loop bodies repeated? What is the final output in each case?

int z = 2;
while (z < 20)
    if ((z++) % 2 == 0) 
        System.out.println(z);

What is the output produced by the following code?

int n = 20;
do   {
    System.out.println(n);
    n = n - 3; 
} while (n > 0);

What is the output produced by the following code?

int num = 20;
while (num > 0) 
{
    num = num - 2;
    if (num == 4)
        break ;
    System.out.println(num);
}
System.out.println("Finished");

What is the output produced by the following code?

int num = 10;
while (num > 0)
{
    num = num - 2;
    if (num == 2)
        continue;   
    System.out.println(num);
}
System.out.println("Finished");

Write a program to input n number of integers and find out:

i. Number of positive integers

ii. Number of negative integers

iii. Sum of positive numbers

iv. Product of negative numbers

v. Average of positive numbers

import java.util.Scanner;

public class KboatIntegers
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        int pSum = 0, pCount = 0, nPro = 1, nCount = 0;
        System.out.println("Enter n:");
        int n = in.nextInt();
        
        System.out.println("Enter " + n + " integers:");
        for (int i = 1; i <= n; i++) {
            int num = in.nextInt();
            if (num >= 0) {
                pSum += num;
                pCount++;
            }
            else {
                nPro *= num;
                nCount++;
            }
        }
        
        double pAvg = pSum/(double)pCount;
        System.out.println("Positive Integers = " + pCount);
        System.out.println("Negative Integers = " + nCount);
        System.out.println("Sum of Positive = " + pSum);
        System.out.println("Product of Negative = " + nPro);
        System.out.println("Average of Positive = " + pAvg); 
        
    }
}

Write a program using do-while loop to compute the sum of the first 500 positive odd integers.

public class KboatSumOdd
{
    public static void main(String args[]) {
        long sumOdd = 0;  
        int num = 1;
        do  {
            sumOdd += num;
            num += 2;
        }while(num <= 500);
                    
        System.out.println("Sum of 500 odd positive numbers = "
                            + sumOdd);        
    }
}

Write three different programs using for, while, and do-while loops to find the product of series 3, 9, 12,... 30.

public class KBoatSeries
{
    public static void main(String args[]) {
        int pro = 1;
        for(int i = 3, t = 1; i <= 30; t++) { 
            pro *= i;
            if(t % 2 == 0)
                i += 3;
            else
                i += 6;
        }
        System.out.println("Product = " + pro);
    }
}

public class KBoatSeries
{
    public static void main(String args[]) {
        long pro = 1;  
        int num = 3, t = 1;
        
        while(num <= 30)    {
            pro *= num;
            if(t % 2 == 0)
                num += 3;
            else
                num += 6;
            t++;
        }            
        System.out.println("Product = " + pro);
    }
}

public class KBoatSeries
{
    public static void main(String args[]) {
        long pro = 1;  
        int num = 3, t = 1;
        
        do {
            pro *= num;
            if(t % 2 == 0)
                num += 3;
            else
                num += 6;
            t++;
        } while(num <= 30);
                    
        System.out.println("Product = " + pro);
    }
}

Write a program to convert kilograms to pounds in the following tabular format (1 kilogram is 2.2 pounds):

public class KboatKiloToPound
{
    public static void main(String args[]) {
        System.out.println("Kilograms \t Pounds");
        for(int i = 1; i <= 20; i++) {
            double p = i * 2.2;
            System.out.println(i + "\t\t" + p);
        }
    }
}

Write a program that displays all the numbers from 150 to 250 that are divisible by 5 or 6, but not both.

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

        for (int i = 150; i <= 250; i++) {
            int mod5 = i % 5;
            int mod6 = i % 6;
            
            if ((mod5 == 0 || mod6 == 0) 
                    && !(mod5 == 0 && mod6 == 0)) {
                System.out.println(i);
            }
        }
    }
}

Write a program in Java to read a number and display its digits in the reverse order. For example, if the input number is 2468, then the output should be 8642.

Output:
Enter a number: 2468
Original number: 2468
Reverse number: 8642

import java.util.Scanner;

public class KboatDigitReverse
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        System.out.print("Enter Number: ");
        int orgNum = in.nextInt();
        
        int copyNum = orgNum;
        int revNum = 0;
        
        while(copyNum != 0) {
            int digit = copyNum % 10;
            copyNum /= 10;
            revNum = revNum * 10 + digit;
        }
        
        System.out.println("Original Number = " + orgNum);
        System.out.println("Reverse Number = " + revNum);
    }
}

Write a program in Java to read a number, remove all zeros from it, and display the new number. For example,

Sample Input: 45407703
Sample Output: 454773

import java.util.Scanner;

public class KboatRemoveZeros
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter number: ");
        int num = in.nextInt();
        int idx = 0;
        int newNum = 0;
        int n = num;
        
        while (n != 0) {
            int d = n % 10;
            if (d != 0) {
                newNum += (int)(d * Math.pow(10, idx));
                idx++;
            }
            n /= 10;
        }
        
        System.out.println("Original number = " + num);
        System.out.println("New number = " + newNum);
    }
}

Write a program to read the number n using the Scanner class and print the Tribonacci series: 0, 0, 1, 1, 2, 4, 7, 13, 24, 44, 81 ...and so on.
Hint: The Tribonacci series is a generalisation of the Fibonacci sequence where each term is the sum of the three preceding terms.

import java.util.Scanner;

public class KboatTribonacci
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter no. of terms : ");
        int n = in.nextInt();
        
        if(n < 3)
            System.out.print("Enter a number greater than 2");
        else    {
            int a = 0, b = 0, c = 1;
            System.out.print(a + " " + b + " " + c);
        
            for (int i = 4; i <= n; i++) {
                int term = a + b + c;
                System.out.print(" " + term);
                a = b;
                b = c;
                c = term;
            }
        }
    }
}

Write a program to calculate the value of Pi with the help of the following series:
Pi = (4/1) - (4/3) + (4/5) - (4/7) + (4/9) - (4/11) + (4/13) - (4/15) ...
Hint: Use while loop with 100000 iterations.

public class KboatValOfPi
{
        public static void main(String args[]) {
            double pi = 0.0d, j = 1.0d;
            int i = 1;
            while(i <= 100000)  {
                if(i % 2 == 0)
                    pi -= 4/j;
                else
                    pi += 4/j;
                j += 2;
                i++;
            }
            System.out.println("Pi = " + pi);
        
    }
}

Write a program to display the following patterns as per the user's choice.

Pattern 1	       
I
 C
   S
     E

Pattern 2
      I
    C
  S
E

import java.util.Scanner;

public class KboatMenuPattern
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter 1 for Pattern 1");
        System.out.println("Enter 2 for Pattern 2");
        System.out.print("Enter your choice: ");
        int ch = in.nextInt();
        String str = "ICSE";
        int len = str.length();
        switch (ch) {
            case 1:
                for (int i = 0; i < len; i++) {
                    for (int j = 0; j < i; j++) {
                        System.out.print(" ");
                    }
                    System.out.println(str.charAt(i));
                }
                break;

            case 2:
                for (int i = len - 1; i >= 0; i--) {
                    for (int j = 0; j < i; j++) {
                        System.out.print(" ");
                    }
                    System.out.println(str.charAt(len - 1 - i));
                }
                break;

            default:
            System.out.println("Incorrect choice");
            break;

        }
    }
}

Write a menu-driven program to display the pattern as the per user's choice:

Pattern 1
ABCDE
ABCD
ABC
AB
A

Pattern 2
B
LL
UUU
EEEE

For an incorrect option, an appropriate error message should be displayed.

import java.util.Scanner;

public class KboatMenuPattern
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter 1 for pattern 1");
        System.out.println("Enter 2 for Pattern 2");
        System.out.print("Enter your choice: ");
        int choice = in.nextInt();
        switch (choice) {
            case 1:
            for (int i = 69; i >= 65; i--) {
                for (int j = 65; j <= i; j++) {
                    System.out.print((char)j);
                }
                System.out.println();
            }
            break;

            case 2:
            String word = "BLUE";
            int len = word.length();
            for(int i = 0; i < len; i++) {
                for(int j = 0; j <= i; j++) {
                    System.out.print(word.charAt(i));
                }
                System.out.println();
            }
            break;

            default:
            System.out.println("Incorrect choice");
            break;

        }
    }
}

Write a program to input a number and check and print whether it is a Pronic number or not. (Pronic number is a number which is the product of two consecutive integers.)
Example: 12 = 3 x 4
                20 = 4 x 5
                42 = 6 x 7

import java.util.Scanner;

public class KboatPronicNumber
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter the number to check: ");
        int num = in.nextInt();
        
        boolean isPronic = false;
        
        for (int i = 1; i <= num - 1; i++) {
            if (i * (i + 1) == num) {
                isPronic = true;
                break;
            }
        }
        
        if (isPronic)
            System.out.println(num + " is a pronic number");
        else
            System.out.println(num + " is not a pronic number");
    }
}

Write a program to accept a number and check and display whether it is a spy number or not. (A number is called a spy number if the sum of its digits equals the product of the digits.)
Example:
Consider the number 1124.
Sum of the digits = 1 + 1 + 2 + 4 = 8.
Product of the digits = 1 * 1 * 2 * 4 = 8.
Refer to Program 9.44 for the solution.

import java.util.Scanner;

public class KboatSpyNumber
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Enter Number: ");
        int num = in.nextInt();
        
        int digit, sum = 0;
        int orgNum = num;
        int prod = 1;
        
        while (num > 0) {
            digit = num % 10;
            
            sum += digit;
            prod *= digit;
            num /= 10;
        }
        
        if (sum == prod)
            System.out.println(orgNum + " is Spy Number");
        else
            System.out.println(orgNum + " is not Spy Number");
        
    }
}

Write a program to accept a number and check and display whether it is a Niven number or not. (Niven number number which is divisible by the sum of its digits).
Example:
Consider the number 126.
Sum of its digits is 1 + 2 + 6 = 9 and 126 is divisible by 9. Refer to Program 9.45 for the solution.

import java.util.Scanner;

public class KboatNivenNumber
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter number: ");
        int num = in.nextInt();
        int orgNum = num;
        
        int digitSum = 0;
        
        while (num != 0) {
            int digit = num % 10;
            num /= 10;
            digitSum += digit;
        }
        
        /*
         * digitSum != 0 check prevents
         * division by zero error for the
         * case when users gives the number
         * 0 as input
         */
        if (digitSum != 0 && orgNum % digitSum == 0)
            System.out.println(orgNum + " is a Niven number");
        else
            System.out.println(orgNum + " is not a Niven number");
    }
}

Using the switch statement, write a menu driven program to:

import java.util.Scanner;

public class KboatFibonacciNDigitSum
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.println("1. Fibonacci Series");
        System.out.println("2. Sum of digits");
        System.out.print("Enter your choice: ");
        int ch = in.nextInt();

        switch (ch) {
            case 1:
            int a = 0, b = 1;
            System.out.print(a + " " + b);
            /*
             * i is starting from 3 below
             * instead of 1 because we have 
             * already printed 2 terms of
             * the series. The for loop will 
             * print the series from third
             * term onwards.
             */
            for (int i = 3; i <= 10; i++) {
                int term = a + b;
                System.out.print(" " + term);
                a = b;
                b = term;
            }
            break;

            case 2:
            System.out.print("Enter number: ");
            int num = in.nextInt();
            int sum = 0;
            while (num != 0) {
                sum += num % 10;
                num /= 10;
            }
            System.out.println("Sum of Digits " + " = " + sum);
            break;

            default:
            System.out.println("Incorrect choice");
            break;
        }
    }
}

Write a menu driven program to accept a number and check and display whether (i) it is a Prime Number or not (ii) it is an Automorphic Number or not. (Use switch-case statement).

import java.util.Scanner;

public class KboatPrimeAutomorphic
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.println("1. Prime number");
        System.out.println("2. Automorphic number");
        System.out.print("Enter your choice: ");
        int choice = in.nextInt();
        System.out.print("Enter number: ");
        int num = in.nextInt();

        switch (choice) {
            case 1:
            int c = 0;
            for (int i = 1; i <= num; i++) {
                if (num % i == 0) {
                    c++;
                }
            }
            if (c == 2) 
                System.out.println(num + " is Prime");
            else
                System.out.println(num + " is not Prime");
            break;

            case 2:
            int numCopy = num;
            int sq = num * num;
            int d = 0;

            /*
             * Count the number of 
             * digits in num
             */
            while(num > 0) {
                d++;
                num /= 10;
            }

            /*
             * Extract the last d digits
             * from square of num
             */
            int ld = (int)(sq % Math.pow(10, d));

            if (ld == numCopy)
                System.out.println(numCopy + " is automorphic");
            else
                System.out.println(numCopy + " is not automorphic");
            break;

            default:
            System.out.println("Incorrect Choice");
            break;
        }
    }
}

Write a menu driven program to accept a number from the user and check whether it is a BUZZ number or to accept any two numbers and to print the GCD of them.

1. A BUZZ number is the number which either ends with 7 or is divisible by 7.
2. GCD (Greatest Common Divisor) of two integers is calculated by continued division method. Divide the larger number by the smaller; the remainder then divides the previous divisor. The process is repeated till the remainder is zero. The divisor then results the GCD.

import java.util.Scanner;

public class KboatBuzzGCD
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.println("1. Buzz number");
        System.out.println("2. Calculate GCD");
        System.out.print("Enter your choice: ");
        int choice = in.nextInt();

        switch (choice) {
            case 1:
                System.out.print("Enter a number: ");
                int num = in.nextInt();
                if (num % 10 == 7 || num % 7 == 0)
                    System.out.println(num + " is a Buzz Number");
                else
                    System.out.println(num + " is not a Buzz Number");
            break;

            case 2:
                System.out.print("Enter first number: ");
                int a = in.nextInt();
                System.out.print("Enter second number: ");
                int b = in.nextInt();
                while (b != 0) {
                    int t = b;
                    b = a % b;
                    a = t;
                }
                System.out.println("GCD = " + a);
                break;

            default:
            System.out.println("Incorrect Choice");
            break;
        }
    }
}

Write a program to read the number x using the Scanner class and compute the series:

Sum = x/2 + x/5 + x/8 + x/11+ ..... + x/20

The output should look like as shown below:

Enter the value of x: 10
Sum of the series is: 10.961611917494269

import java.util.Scanner;

public class KboatSeries
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter x: ");
        int x = in.nextInt();
        double sum = 0.0;
        for (int i = 2; i <= 20; i += 3)
            sum += (double)x / i;
        System.out.println("Sum = " + sum);
    }
}

Write a program in Java to compute and display factorial of numbers up to a number entered via the Scanner class. The output should look like as shown below when 7 is input.

Enter a number: 7
1! (=1) = 1
2! (= 1 x 2) = 2
3! (= 1 x 2 x 3) = 6
4! (= 1 x 2 x 3 x 4) = 24
5! (= 1 x 2 x 3 x 4 x 5) = 120
6! (= 1 x 2 x 3 x 4 x 5 x 6) = 720
7! (= 1 x 2 x 3 x 4 x 5 x 6 x 7) = 5040

import java.util.Scanner;

public class KboatFactorial
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter a number: ");
        int num = in.nextInt();
        
        for (int i = 1; i <= num; i++)  {
            int f = 1;
            System.out.print(i + "! ( = ");
            for (int j = 1; j <= i; j++)    {
                if (j == 1)
                    System.out.print(j);
                else
                    System.out.print(" x " + j);
                f *= j;
            }
            System.out.print(" ) = " + f);
            System.out.println();
        }
    }
}

Write a program in Java to find the sum of the given series:

x¹ + x² + x³ + x⁴ + ..... + xⁿ

import java.util.Scanner;

public class KboatSeries
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter x: ");
        int x = in.nextInt();
        System.out.print("Enter n: ");
        int n = in.nextInt();
        long sum = 0;
        for (int i = 1; i <= n; i++)
            sum += Math.pow(x, i);
        System.out.println("Sum = " + sum);
    }
}

Write a program in Java to find the sum of the given series:

x¹ - x² + x³ - x⁴ + ..... - xⁿ , where x = 3

import java.util.Scanner;

public class KboatSeries
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter n: ");
        int n = in.nextInt();
        int x = 3;
        double sum = 0;
        
        for (int i = 1; i <= n; i++) {
                double term = Math.pow(x, i);
                if (i % 2 == 0)
                    sum -= term;
                else
                    sum += term;
            }
            System.out.println("Sum = " + sum);
    }
}

Write a program in Java to find the sum of the given series:

$\frac{1}{x^1} + \frac{2}{x^2} + \frac{3}{x^3} + ... + \frac{n}{x^n}$

import java.util.Scanner;

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

        Scanner in = new Scanner(System.in);
        System.out.print("Enter x: ");
        int x = in.nextInt();
        System.out.print("Enter n: ");
        int n = in.nextInt();
        double sum = 0;

        for (int i = 1; i <= n; i++) {
            sum += (i / Math.pow(x, i));
        }
        
        System.out.println("Sum=" + sum);
    }
}

Write a program in Java to find the sum of the given series:

$\frac{1}{2} + \frac{2}{3} + \frac{3}{4} + ... + \frac{49}{50}$

import java.util.Scanner;

public class KboatSeries
{
    public static void main(String args[]) {
        double sum = 0;
        for (int i = 1; i <= 49; i++)
            sum += i / (double)(i + 1);
        System.out.println("Sum = " + sum);
    }
}

Write a program in Java to find the sum of the given series:

$\frac{1}{\sqrt{1}} + \frac{2}{\sqrt{2}} + \frac{3}{\sqrt{3}} + ... + \frac{10}{\sqrt{10}}$

public class KboatSeries
{
    public static void main(String args[]) {    
        double sum = 0;
        for (int i = 1; i <= 10; i++)
            sum += i / Math.sqrt(i);
        System.out.println("Sum = " + sum);
    }
}

Write a program in Java to find the sum of the given series:

$\frac{x + 1}{3} + \frac{x + 2}{5} + \frac{x + 3}{7} + ...\text{to n terms}$

import java.util.Scanner;

public class KboatSeries
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter n: ");
        int n = in.nextInt();
        System.out.print("Enter x: ");
        int x = in.nextInt();

        double sum = 0;
        for (int i = 1, j = 3; i <= n; i++, j += 2) {
            sum += (x + i) / (double)j;
        }
        System.out.println("Sum = " + sum);
    }
}

Write a program in Java to find the sum of the given series:

$\frac{x}{2!} + \frac{x}{3!} + \frac{x}{4!} + ... + \frac{x}{20!}$

import java.util.Scanner;

public class KboatSeries
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter x: ");
        int x = in.nextInt();
        double sum = 0;
        
        for (int i = 2; i <= 20; i++) {
            double f = 1;
            for (int j = 1; j <= i; j++) {
                f *= j;
            }
            sum += x / f;
        }
        System.out.println("Sum = " + sum);
        
    }
}

Write a program in Java to find the sum of the given series:

$\frac{x^2}{2!} + \frac{x^3}{3!} + \frac{x^4}{4!} + ... + \frac{x^n}{n!}, \text{where n = 10}$

import java.util.Scanner;

public class KboatSeries
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter x: ");
        int x = in.nextInt();
        double sum = 0;
        
        for (int i = 2; i <= 10; i++) {
            double f = 1;
            for (int j = 1; j <= i; j++) {
                f *= j;
            }
            double term = Math.pow(x,i) / f;
            sum += term;
        }
        System.out.println("Sum = " + sum);
        
    }
}

Write a program in Java to find the sum of the given series:

1 + 3 + 7 + 15 + 31 + ..... + (2²⁰ - 1)

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

        double sum = 0;
        
        for (int i = 1; i <= 20; i++) {
            double term = Math.pow(2,i) - 1;
            sum += term;
        }
            
        System.out.println("Sum = " + sum);
        
    }
}

Write a program in Java to find the sum of the given series:

1 * 2 * 4 * 8 * ..... * 2²⁰

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

        double sum = 0;
        
        for (int i = 0; i <= 20; i++) {
            double term = Math.pow(2,i);
            sum += term;
        }
            
        System.out.println("Sum = " + sum);
        
    }
}

Write a menu driven class to accept a number from the user and check whether it is Palindrome or a Perfect number.

import java.util.Scanner;

public class KboatPalinOrPerfect
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.println("1. Palindrome number");
        System.out.println("2. Perfect number");
        System.out.print("Enter your choice: ");
        int choice = in.nextInt();
        System.out.print("Enter number: ");
        int num = in.nextInt();

        switch (choice) {
            case 1:
            int copyNum = num;
            int revNum = 0;

            while(copyNum != 0) {
                int digit = copyNum % 10;
                copyNum /= 10;
                revNum = revNum * 10 + digit;
            }

            if (revNum == num) 
                System.out.println(num + " is palindrome");
            else
                System.out.println(num + " is not palindrome");
            break;

            case 2:
            int sum = 0;

            for (int i = 1; i <= num / 2; i++) {
                if (num % i == 0) {
                    sum += i;
                }
            }

            if (num == sum) 
                System.out.println(num + " is a perfect number");
            else
                System.out.println(num + " is not a perfect number");
            break;

            default:
            System.out.println("Incorrect Choice");
            break;
        }
    }
}

Write a program to print the sum of negative numbers, sum of positive even numbers and sum of positive odd numbers from a list of n numbers entered by the user. The program terminates when the user enters a zero.

import java.util.Scanner;

public class KboatNumberSum
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        int nSum = 0, eSum = 0, oSum = 0;
        System.out.println("Enter Numbers:");
        while (true) {
            int n = in.nextInt();
            
            if (n == 0) {
                break;
            }
            
            if (n < 0) {
                nSum += n; 
            }
            else if (n % 2 == 0) {
                eSum += n;
            }
            else {
                oSum += n;
            }
        }
        
        System.out.println("Negative No. Sum = " + nSum);
        System.out.println("Positive Even No. Sum = " + eSum);
        System.out.println("Positive Odd No. Sum = " + oSum);
    }
}