Chapter16

import java.util.*;

public class Member {

    public static void main(String[] args) {
        // Basic i/o
        Scanner keyboard = new Scanner(System.in);
        System.out.print("Enter size of array:");
        String input = keyboard.nextLine();
        int sizeOfArray = Integer.parseInt(input);

        int[] myIntArray = new int[sizeOfArray];

        for(int i = 0; i < sizeOfArray; i++){
            System.out.print("Enter number for array index " + i + ":");
            input = keyboard.nextLine();
            myIntArray[i] = Integer.parseInt(input);
        }


        System.out.print("Enter number to search for in array:");
        input = keyboard.nextLine();
        int search = Integer.parseInt(input);

        if(isMember(myIntArray, search)){System.out.println("true");}
        else{System.out.println("false");};

    }

    public static boolean isMember(int[] array, int value) {
        if(array.length == 0) {return false;}
        if(array[0] == value) {return true;}
        int[] array2 = new int[array.length-1];
        System.arraycopy(array,1,array2,0,array2.length);
        return isMember(array2, value);          
    }
}

import java.util.Scanner;

public class StringReverse {

    public static void main(String[] args) {
        // Basic i/o
        System.out.print("Enter a string to be reversed:");
        Scanner keyboard = new Scanner(System.in);
        String name1 = keyboard.nextLine();
        System.out.print(reverse(name1));
    }
    public static String reverse(String s){
    if (s.length() == 0) 
         return s;

    return reverse(s.substring(1)) + s.charAt(0);
}
}

import java.util.Scanner;
public class Multiplication {

    public static void main(String[] args) {
        // Basic i/o
        System.out.print("Enter a value for x:");
        Scanner keyboard = new Scanner(System.in);
        int x = keyboard.nextInt();
        System.out.print("Enter a value for y:");
        int y = keyboard.nextInt();
        System.out.print("The product of " + x + " * " + y + " is " + product(x,y));
    }

    public static int product(int num1, int num2) { 
    if (num1 == 0 || num2 == 0) {
        return 0;
}

else if( num2 < 0 ) {
    return - num1 + product(num1, num2 + 1);
}

else {
    return num1 + product(num1, num2 - 1);
}
    }
}

import java.util.Scanner;
public class Palindrome {
    public static void main(String[] args){
        // Basic i/o
        System.out.print("Enter a phrase:");
        Scanner keyboard = new Scanner(System.in);
        String test = keyboard.nextLine();
        test = test.replaceAll("\\W", "");
        test = test.toLowerCase();
        if(isPalindrome(test)){
            System.out.print("That phrase is a palindrome.");
        }else{
            System.out.print("That phrase is not a palindrome.");
        }

    }

    public static boolean isPalindrome(String word) {


              if(word.length() < 2) { return true;  }
              char first  = word.charAt(0);
              char last   = word.charAt(word.length()-1);
              if(  first != last  ) { return false; }
              else { return isPalindrome(word.substring(1,word.length()-1)); }

}
}

import java.util.Scanner;

class SumofNumbers {

    public static void main(String[] args)  {
        // Basic i/o
        System.out.print("Enter a number:");
        Scanner keyboard = new Scanner(System.in);
        int input = keyboard.nextInt();
        while(input < 0){
            System.out.print("Enter a positive value:");
            input = keyboard.nextInt();
        }
        System.out.print("The sum of all numbers up to " + input + " is " + sum(input));
    }
    public static int sum(int n) {
            if (n == 0)
            {
                        return 0;
            }
            else if (n == 1) {
                return 1;
            }
            else
            {
                        return (sum(n-1) + n);
            }
}
}

Lol i couldn't figure this one out. YOLO!