palindrome numbers in java

Im new to java and I was wondering how i would print prime palindrome without using strings and only methods.

This is what I have so far. I want to print every prime palindrome number before 50. I did this with prime numbers only and it was working but when I added in palindrome, it did not work.

EDIT: i added in the int original = number like one of the answers says but my output is always 2,3,5,7,11 and nothing more.

EDIT2(1 more question): I changed the value up to 1000 and my output is 2 3 5 7 11 313 353 373 383 727 757 787 797 919 929. The output is correct but isn't 101, 131, 151, 181, 191 also prime palindrome nu开发者_如何学Cmbers? Why are they not included in the output?

public class primePalindrome {
public static void main (String[] args) {
    Scanner input = new Scanner(System.in);
    System.out.println("Enter a number");
    int num = input.nextInt();
    System.out.println("The prime palindrome numbers are \n");
    printPP(num);
}

public static void printPP(int numberOfPP) {
    final int NUMBER_OF_PP_PER_LINE = 10;
    int count = 0;
    int number = 2;

    while (number < numberOfPP) {
        if(isPrime(number) && isPalindrome(number)) {
            count++;

            if (count % NUMBER_OF_PP_PER_LINE ==0) {
                System.out.printf("%-5s\n", number);
            }
            else
                System.out.printf("%-5s", number);
        }
        number++;
    }
}

public static boolean isPrime(int number) {
    for (int divisor = 2; divisor <= number / 2; divisor++) {
        if (number % divisor == 0) {
            return false;
        }
    }
    return true;
}

public static boolean isPalindrome(int number) {
    int reverse = 0;
    int n = number;
    for (int i = 0; i <= number; i++) {
        int remain = number%10;
        number = number/10;
        reverse = reverse*10+remain;
    }
    if (reverse == n) {
        return true;
    }
}
        return false;

}

}

There's only one 2-digit prime palindrome: 11. Every other 2-digit number is divisible by 11. Your output is thus correct.

Your isPalindrome is quite close: 1) Move the equality check outside the loop 2) Use while-loop. Using "for" results in omitting palindrome patterns 1X1, 2XX2 etc. 3) Dont't forget to preserve the argument:

public static boolean isPalindrome(int number) {
    int original = number;
    int reverse = 0;
    while (number > 0) {
        int digit = number%10;
        number = number/10;
        reverse = reverse*10+remain;
    }
    return reverse == original;
}

You were close. At the end you compare number to reverse. Unfortunately, number has been modified. You need to compare number's original value to reverse. Here's my modified version:

public static boolean isPalindrome(int number) {
    int original = number;
    int reverse = 0;
    for (int i = 0; i <= number; i++) {
        int remain = number % 10;
        number = number / 10;
        reverse = reverse * 10 + remain;
    }
    return reverse == original;
}

/* Palindrome Program In JAVA
  Credit: Code Nirvana (www.codenirvana.in)
*/
import java.util.Scanner;
class Palindrome{ 
     public static void main(String args[]){ 
       System.out.print("Enter Number: ");
       Scanner read = new Scanner(System.in);
       int num = read.nextInt();
       int n = num;
       //reversing number
       int rev=0,rmd; 
       while(num > 0) 
       { 
         rmd = num % 10; 
         rev = rev * 10 + rmd; 
         num = num / 10; 
       } 
       if(rev == n) 
         System.out.println(n+" is a Palindrome Number!"); 
       else 
         System.out.println(n+" is not a Palindrome Number!"); 
     } 
}

Since most of the answers above doesn't work for both positive and negative numbers, following is one which works for negative numbers as well.

private static boolean isPalindrome(int n) {
    int orignal = n, reversed = 0;
    while (n != 0) {
        reversed = (reversed * 10) + (n % 10);
        n /= 10;
    }
    return reversed == orignal;
}

What if the given input is a huge number or a string?

I believe the below code should work for any input.

private boolean isPalindrome(String s) {
    int lo = 0, hi = s.length()-1;
    while(lo < hi) {
        if(s.charAt(lo) == s.charAt(hi)) {
           lo++; hi--;
        } else {
            return false;
        }
    }
    return true;
}

import java.util.Scanner;

/*if given number is same with reverse number 
  then this number is called as Palindrome number. */

public class PalindromeNumber { 
public static void main(String args[])
{
    int input,store,output=0;
    Scanner in=new Scanner(System.in);
    System.out.println("Enter a number for check.");
    input=in.nextInt();
    store=input;
    while (input!=0)
    {   
    output=output*10;
    output=output+input%10;
    input=input/10;
    }
    System.out.println(output);
     if (output == store) 
    {
        System.out.println("This is a palindrome number.");
    }
    else
    {
        System.out.println("This is not a palindrome number.");
    } 

    in.close();
}

}

import java.util.*;
/*
@ Author 12CSE54
@ Date 29.10.14
*/
public class cpalindrome
{
public static void main(String ar[])throws Exception
{
Scanner s=new Scanner(System.in);
System.out.println("Enter the number\n");
int n=sc.nextInt();
int s=0,r;
while(n>0)
{
r=n%10;
s=(s*10)+r;
n/=10;
}
if(n==s)
System.out.println("palindrome\n");
else
System.out.println("not a palindrome");
}
}

import java.util.*;
public class PalPrime
{
    public boolean prime(int n)
    {
         int c=0;
         for(int i=1;i<=n;i++)
         {
             if(n%i==0)
                 c++;
         }
         if(c==2)
             return true;
         else
             return false;
    }

    public boolean palindrome(int n)
    {
         int rev=0,temp=n;
         while(temp!=0)
         {
             rev=rev*10+(temp%10);
             temp=temp/10;
         }
         if(rev==n)
             return true;
         else
             return false;
    }

    public static void main(String args[])
    {
         Scanner ob=new Scanner(System.in);
         System.out.println("Enter number to be checked");
         int num=ob.nextInt();
         PalPrime obj=new PalPrime();
         if(obj.prime(num)==true && obj.palindrome(num)==true)
             System.out.println(num+" is a Prime Palindrome i.e. a PalPrime Number");
         else
             System.out.println(num+" is not a PalPrime Number");
    }
 }

TRY THIS!

This is easy to Understand

public class StringDemo {

 public static void main(String args[]) {
  if(palindrome("1211")){
      System.out.println("Yes IT IS palindrome");
  }
  if(palindrome("121")){
      System.out.println("Yes IT IS palindrome");
  }
  }
  public static boolean palindrome(Object o){
   String s=(String)o;
   boolean result=true;
   int temp=s.length()-1;
   for(int c=0;c<temp;c++){
       if(s.charAt(c)==s.charAt(temp)){
           temp--;
           //System.out.println("Pallidrom start "+ s.charAt(c));
           //System.out.println("Pallidrom end "+ s.charAt(temp));
       }else{
           System.out.println("NOT palindrome");
           return false;
       }
    }
    return result;
 }
}

Result is