Question

Write a main program that runs the following two recursive methods demonstrating that they work. #1) Write a recursive method writeSquares that accepts an integer n and prints the first n squares with the odd squares in decending order, followed by the even squares in acending order. For example • writeSquares(8): prints . 49 25 9 1 4 16 36 64 • writeSquares(11); prints 121 81 49 25 9 1 2 16 36 64 100 • writeSqures(1) prints o 1 • writeSqures(O) (or any negative number) prints o nothing

Please write in java

Answer 1

Please find the running java code below for both the given problems. Please do comments in case of any issue or more information is needed. Also, if you like my work please give it a thumbs up to encourage. Thank You.

You can use any JAVA compiler to run this file. The comments have also been added for code segments for better understanding of the code. The output screenshots have also been attached for your reference.

Question 1:

The logic in the code has been implemented as per the description in the problem. The file name is Main.java

Here I have implemented writeSquares(), a recursive function that accepts an integer n(taken from user/console) and prints odd squares in decending order followed by even squares in acending order.

Java Source Code:

//program that has writeSquares() recursive method that accepts an integer n and prints odd squares in decending order followed by even squares in acending order
import java.util.Scanner; //for taking the input from the user

//Main class
public class Main {

    //writeSquares() function that returns squares String
    // the function first calls  writeOddSquares() to print odd squares
    // followed by writeEvenSquares() to print even squres
    public static String writeSquares(int n) {

        if (n < 1) //if n is less than 1 then print "nothing"
            return "nothing";
        if (n == 1) //if n is 1 then call writeOddSquares()
            return writeOddSquares(n);
        else //otherwise call first call writeOddSquares() and secondaly call writeEvenSquares();
            return writeOddSquares(n) + writeEvenSquares("", n);
    }
    //writeOddSquares() is a recursive function 
    //that returns a String of  the odd squraes in decending order 
    public static String writeOddSquares(int n) {

        //Base case: if n is 1 return 1
        if (n == 1) {
            return 1 + " ";

        } else if (n % 2 != 0) { //otherwise test if number is odd and return squares
            return n * n + " " + writeOddSquares(n - 1);
        }
        return writeOddSquares(n - 1);
    }

    //writeEvenSquares() is a recursive function 
    //that returns a String of  the even squraes in acending order 
    public static String writeEvenSquares(String s, int n) {

        //Base case: if n is 2 return 4
        if (n == 2) {
            return "4";
        } else if (n % 2 == 0) { //otherwise test if number is even and return squares  
            return writeEvenSquares(s, n - 1) + " " + n * n;
        }
        return writeEvenSquares(s, n - 1);

    }
    //main() function to test the functionality
    public static void main(String[] args) {
        int n; //stores the integer entered by User
        Scanner sc = new Scanner(System.in); //create an object of Scanner class
        System.out.print("Please enter an integer:"); //prompt
        n = sc.nextInt(); //read integer n from user
        System.out.println(writeSquares(n)); //call writeSquares() function and display the result
    } //end of main() function
} //end of Main Class

Output:

When you run the above java code and input value is provided as 11 on the console then output is printed on the console as below-

at Main.writeEvenSquares (Main.java:25) > javac -classpath .:/run_dir/junit-4.12.jar:target/dependency/* -d . Main.java >java -classpath .:/run_dir/junit-4.12.jar:target/dependency/* Main Please enter an integer:11 121 81 49 25 9 1 4 16 36 64 100

When you run the above java code and input value is provided as 1 on the console then output is printed on the console as below-

> javac -classpath .:/run_dir/junit-4.12.jar:target/dependency/* -d . Main.java >java -classpath .:/run_dir/junit-4.12.jar:target/dependency/+ Main Please enter an integer:1 1 I

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Question 2:

The logic in the code has been implemented as per the description in the problem. The file name is Main.java

Here I have implemented the isPalindrome(), a recursive function that accepts a String and returns true if String is palindrome otherwise retuns false if it is not palindrome. In the main() function we have also tested the isPalindrome() function functionality by passing String values taken from user and print result either true or false depending on the string.

Source Code:

//program that has isPalindrome() recursive method that accepts a String and returns true if String is palindrome otherwise retuns false if it is not palindrome. In the main() function we test the isPalindrome() by passing string values taken from user and print result.
import java.util.Scanner; //for taking the input from the user
//Main class
class Main {

    //isPalindrome() a recursive function  takes a String 
    //and returns true if the string is palindrome
    //otherwise returns false if String is not palindrome
    public static boolean isPalindrome(String s) { // Base case: if length is 0 or 1 then String is palindrome
        if (s.length() == 0 || s.length() == 1)
            return true;
        //checking for first and last character of String,
        // if they are same then we will do the same thing
        // for a substring with first and last character being removed.
        // and we will carry on this until the condition fails or base case is executed
        if (s.charAt(0) == s.charAt(s.length() - 1))
            return isPalindrome(s.substring(1, s.length() - 1)); //recursive call
        //otherwise return false since palindrome condition gets failed
        return false;
    }
    //main() function to test isPalindrome() function
    public static void main(String[] args) {
        //creating instance sc of Scanner Class to take input from user
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter the String for checking palindrome : "); //prompt
        String string = sc.nextLine(); //read String from user/console

        System.out.println(isPalindrome(string)); //calling isPalindrome() function and print result

    }
}

Output:

When you run the above java code and input string is provided as madam on the console then output is printed on the console as below-

> javac -classpath .:/run_dir/junit-4.12.jar:target/dependency/* -d > javac -classpath ./run dir/junit-4.12.jar:target/dependency/* -d . Main.java >java -classpath .:/run_dir/junit-4.12.jar:target/dependency/* Main Enter the String for checking palindrome : madam true

When you run the above java code and input string is provided as notion on the console then output is printed on the console as below-

>javac -classpath .:/run_dir/junit-4.12.jar:target/dependency/* -d . Main.java >java -classpath .:/run_dir/junit-4.12.jar:target/dependency/* Main Enter the string for checking palindrome : notion false