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Please have a look at the following code
public class Prime
{
public static void main(String[]args)
{
int i = 2;
int counter = 0;
while(true)
{
if(counter==6)//Count still 6
{
break;
}
else
{
if(getPrimes(i)==true)
{
i++;
counter++;
System.out.println("Counter: "+counter);
}
else
{
System.out.println("No");
}
}
}
}
static boolean getPrimes(int num)
{
boolean result = false;
int i = 2;
while(true)
{
if((num%i) != 0) //if the number cannot be divided by any other number (except 1 and it self) it is prime
{
result = true;
System.out.println(num);
System.out.println("I is: "+i);
i=2;
break;
}
else //Not a prime. Repeat the process
{
result = false;
i++;
}
}
return result;
}
}
In here, I am trying to get all the prime numbers between 0-6. This is the test case to get thousands of prime numbers from a really big number. However, it is not showing the only primes, it is showing each and every number!
What am I doing here wrong? Please help!
try this answer...in ur loop
static boolean getPrimes(int num)
{
boolean result=true; // incase u gave 1 or 2 as input.....
int i = 2;
int mid=num/2;
while(i<mid)
{
if(num%i==0)
{
result=false; // not a prime and breaks...
break;
}
else
{
result=true; // the loop make result as true.....
}
i++;
}
return result;
}
I think you need something like this:
public void getPrimes(int a){
for(int i = 2; i < a; i++){
int inCounter = 0;
if(counter%i==0){
System.out.println("false");
inCounter++;
}
if(inCounter == 0){
System.out.println("Prime: "+counter);
}
}
}
Use a sieve, either Eratosthenes or Atkins
Here's the Eratosthenes implementation by Robert Sedgewick in Java:
http://introcs.cs.princeton.edu/java/14array/PrimeSieve.java.html
I guess I found the solution. At least, I found the answer I need. Here is my answer
import java.math.BigInteger;
public class Problem7
{
public static void main(String[]args)
{
int i = 0;
int counter = 0;
while(true)
{
if(i>6)
{
break;
}
if(i>1)
{
String str = String.valueOf(i);
if (new BigInteger(str).isProbablePrime(i/2))
{
System.out.println(str);
counter++;
}
}
i++;
}
}
}
I guess this is the easiest way...
import java.util.Scanner;
class PrimeNumbers2
{
public static void main (String[] args)
{
Scanner scanner = new Scanner(System.in);
int i =0;
int num =0;
//Empty String
String primeNumbers = "";
System.out.println("Enter the value of n:");
int n = scanner.nextInt();
for (i = 1; i <= n; i++)
{
int counter=0;
for(num =i; num>=1; num--)
{
if(i%num==0)
{
counter = counter + 1;
}
}
if (counter ==2)
{
//Appended the Prime number to the String
primeNumbers = primeNumbers + i + " ";
}
}
System.out.println("Prime numbers from 1 to n are :");
System.out.println(primeNumbers);
}
}
it will display all the prime number.
Find Prime number with minimum iteration
boolean IsPrimeNumber(int num) {
boolean isPrime = true;
if (num == 1 || num ==0)
isPrime = false;
else{
int limit = (int) Math.sqrt(num);
for (long i = 2L; i <=limit ; i++)
if (num % i == 0) {
isPrime = false;
break;
}
}
return isPrime;
}
Related
So my professor had us do an assignment that asks the user for 5 numbers that are valid (51-99) and unique (non-repeating). I just can't figure out why my nested for loop inside the while loop is not incrementing the i, I suspect it is the break; but without that the for loop keeps looping. Any help would be awesome. Thank you.
public static void main(String[] args) {
int[] userArray;
userArray = new int[5];
int real = 0;
System.out.println("Please print out 5 numbers between 50 and 100. ");
Scanner entry = new Scanner(System.in);
while (real < 5) {
int count = entry.nextInt();
boolean aCount = isValid(count);
if (aCount == true) {
for (int i =0; i < userArray.length; i++) {
userArray[i] = count;
real++;
break;
}
} else {
System.out.println("That is not a valid number.");
}
}
}
public static boolean isValid(int a) {
if (a > 50 && a < 100) {
return true;
} else {
return false;
}
}
I got it guys! I just had to remove the for loop and put this in:
userArray[i] = count;
i++;
real++;
Thank you schmidt73 and everyone that helped!
int i=0;
while (real < 5) {
int count = entry.nextInt();
boolean aCount = isValid(count);
if (aCount == true) {
userArray[i++] = count;
real++;
} else {
System.out.println("That is not a valid number.");
}
}
I guess this is what you are trying to do.
First, you also need to test if the array contains the value you are trying to add (in validate). You could do something like
public static boolean isValid(int[] arr, int real, int a) {
if (a > 50 && a < 100) {
for (int i = 0; i < real; i++) {
if (arr[i] == a) {
return false;
}
}
return true;
}
return false;
}
Then your main method might be written like
int[] userArray = new int[5];
int real = 0;
System.out.println("Please print out 5 numbers between 50 and 100. ");
Scanner entry = new Scanner(System.in);
while (real < 5) {
int count = entry.nextInt();
if (isValid(userArray, real, count)) {
userArray[real++] = count;
} else {
System.out.println("That is not a valid number.");
}
}
System.out.println("The array contains: " + Arrays.toString(userArray));
This code is to print the series of prime number up to given limit but when I am trying to execute this,it goes into infinite loop.
import java.io.*;
class a
{
public static void main(String s[]) throws IOException
{
int count=1;
String st;
System.out.println("how many prime no. do you want");
BufferedReader obj= new BufferedReader (new InputStreamReader (System.in));
st=obj.readLine();
int n=Integer.parseInt(st);
while(count!=n)
{
int num=2;
for(int i=2;i<num;i++)
{
if(num%i==0)
{
count++;
break;
}
}
num++;
}
}
}
USe isPrime(int num) method in loop to generate prime numbers example is show below code
public class PrimeNumbersSeries
{
public boolean isPrime(int num)
{
boolean flag=true;
for(int i=2; i<=num/2; i++)
{
if(num%i==0)
{
flag=false;
}
else
{
flag=true;
}
}
if(num<=1)
{
flag=false;
}
return flag;
}
public static void main(String []args)
{
System.out.println("how many prime no. do you want");
PrimeNumbersSeries prime=new PrimeNumbersSeries();
Scanner sc=new Scanner(System.in);
int num=sc.nextInt();
int count =0;
int j=1;
while(count!=num)
{
if(prime.isPrime(j))
{
System.out.print(j+", ");
count++;
}
j++;
}
}
}
Problem is value of num is always 2 at the start of loop,even if you say num++ again it takes num=2 which is start statement and wont enter into for loop ever,hence so infinite loop.This will Work
int num=2;
while(count!=n) {
for(int i=2;i<num;i++) {
if(num%i==0) {
count++;
break;
}
}
num++;
}
Here is your working code:
import java.io.*;
class A
{
public static void main(String s[]) throws IOException
{
int count=2;
String st;
System.out.println("how many prime no. do you want");
BufferedReader obj= new BufferedReader (new InputStreamReader (System.in));
st=obj.readLine();
boolean isPrime = false;
int n= Integer.parseInt(st);
int num=3;
if(n>=1){
System.out.println(2);
}
while(count<=n)
{
//No need to go up to num. Up to sqrt(num) will do.
for(int i=2;i<=Math.sqrt(num);i++)
{
if(num%i==0)
{
isPrime = false;
break;
}
}
if(isPrime){
System.out.println(num);// Added the print
count++;
}
isPrime = true;
num++;
}
}
}
After correction i got the series of prime numbers.
import java.io.*;
class a
{
public static void main(String s[]) throws IOException
{
int count=1,count1=0;
String st;
System.out.println("how many prime no. do you want");
BufferedReader obj= new BufferedReader (new InputStreamReader (System.in));
st=obj.readLine();
int n=Integer.parseInt(st);
int num=2;
while(count<=n)
{
count1=0;
for(int i=2;i<num;i++)
{
if(num%i==0)
{
count1++;
}
}
if(count1==0)
{
System.out.println(num);
count++;
}
num++;
}
}
}
You can take a look at this code.
import java.io.*;
public class Main {
public static void main(String[] args) throws IOException {
BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
//How many prime numbers you want to print?
String s = bf.readLine();
int n = Integer.parseInt(s);
int count = 0;
boolean loop = true;
for(int i =2 ; loop ; i++){
if(isPrime(i))
{
System.out.println(i + " ");
count++;
}
if(count == n)
loop = false;
}
}
The following isPrime() method checks whether a number is prime or not. If the number is prime, it returns true, otherwise false.
public static boolean isPrime(int num) {
boolean prime = true;
for(int i=2 ; i<= Math.sqrt(num);){
if(num % i == 0)
{
prime = false;
break;
}
if(i >= 3)
/* when i>=3 we do not need to check for every number.
For avoiding even numbers i is incremented by 2.
It reduces the number of looping */
i+=2;
else
i++;
}
return prime;
}
}
import java.util.*;
class Prime
{
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("enter the no of prime nos want: ");
int n2 = sc.nextInt();
int flag = 1 ;
int count = 0 ;
for (int i =2; i<99999;i++ )
{
for (int j=2; j<i;j++ )
{
if (i%j == 0)
{
flag = 0;
break;
}
else
{
flag =1;
}
}
if (flag == 1)
{
System.out.print(i +"\t");
count++ ;
}
if (count == n2)
{
break ;
}
}
}
}
My program seems to work with numbers '25, 223, and 11" but i have no idea why it stops when i enter the numbers 10 or 100. Any ideas? Any help on this matter will be greatly appreciated-thank you in advance.
*****Source Code*****
import java.util.Scanner;
public class hw_5 {
public static void main(String[] args) {
Scanner inputReader = new Scanner(System.in);
int num;
boolean primeTest;
System.out.print("Enter an integer value: ");
num = inputReader.nextInt();
if(num != -1) {
primeTest = calcPrime(num);
if(!primeTest) {
System.out.println(num+" is not prime.");
printFactors(num);
}
}
}
public static boolean calcPrime(int num) {
for(int i = 2; i < num; i++) {
if(num % i == 0)
return true; // If number is divisible by any number, return true.
}
return false; // If loop exits (means, number was not divisible by any number), return false.
}
public static void printFactors(int num) {
int nFactors = 0;
for(int i = 2; i < num; i++) {
if(num % i == 0) {
System.out.println(num+" is divisible by "+i);
nFactors++;
}
}
System.out.println(num+" has "+nFactors+" factors");
}
}
import java.util.Scanner;
public class Test {
public static boolean calcPrime(int num) {
for(int i = 2; i < num; i++) {
if(num % i == 0)
return false; // If number is divisible by any number, return false.
}
return true; // If loop exits (means, number was not divisible by any number), return true.
}
public static void printFactors(int num) {
int nFactors = 0;
for(int i = 2; i < num; i++) {
if(num % i == 0) {
System.out.println(num+" is divisible by "+i);
nFactors++;
}
}
System.out.println(num+" has "+nFactors+" factors");
}
public static void main(String[] args) {
Scanner inputReader = new Scanner(System.in);
int num = 0;
boolean primeTest = false;
while(true) {
System.out.print("Enter an integer value: ");
num = inputReader.nextInt();
if(num == -1)
break;
primeTest = calcPrime(num);
if(primeTest)
System.out.println(num+" is prime.");
else {
System.out.println(num+" is not prime.");
printFactors(num);
}
}
}
}
Your prime test is wrong :
public static int calcPrime(int number) {
int primer = number % 2;
return primer;
}
It just tests if the number is odd.
Below method returns true if it is a prime number ,
boolean isPrime(int n) {
//check if n is a multiple of 2
if (n%2==0) return false;
//if not, then just check the odds
for(int i=3;i*i<=n;i+=2) {
if(n%i==0)
return false;
}
return true;
}
You could add the numbers to the list and get the their values on iterating back
I want to display the prime number required by the user. For example, if the user wants 3rd prime, I will display 5. I have the following java code.
import java.util.Scanner;
public class Prime {
private static Scanner scanner;
public static void main(String args[]) {
//get input till which prime number to be printed
// System.out.println("Enter which prime number to be printed: ");
// scanner = new Scanner(System.in);
// int limit = scanner.nextInt();
int count = 0;
int number = 2;
//System.out.println("Printing prime number from 1 to " + limit);
while(count<=3)
{
if(isPrime(number)){
count++;
// System.out.println(count);
}
number++;
}
if(count == 3)
System.out.println("10001 prime is "+number);
}
public static boolean isPrime(int number){
for(int i=2; i<number; i++){
if(number%i == 0){
return false;
}
}
return true;
}
}
When i run it, I am not able to gett any output. Where am i going wrong?
PS: For time being, I am running the loop only until 3.
You have while(count <= 3) so when you exit the loop, count == 4.
Therefore, your if(count == 3) is never entered and nothing is printed.
Anyways the better solution would be
public void calcPrime(int inp) {
ArrayList<Integer> arr = new ArrayList<Integer>();
arr.add(2);
arr.add(3);
int counter = 4;
while(arr.size() < inp) {
if(counter % 2 != 0 && counter%3 != 0) {
int temp = 4;
while(temp*temp <= counter) {
if(counter % temp == 0)
break;
temp ++;
}
if(temp*temp > counter) {
arr.add(counter);
}
}
counter++;
}
System.out.println("finish" +arr.get(inp-1));
}
}
Here is corrected code that works.
public class Main {
public static void main(String args[]) {
//Returns fourth prime number
System.out.println(getPrimeNumber(4));
}
public static int getPrimeNumber(int order) {
int currentOrder = 1;
int currentNumber = 1;
while (currentOrder < order) {
currentNumber++;
if (isPrime(currentNumber)) currentOrder++;
}
return currentNumber;
}
public static boolean isPrime(int number) {
for (int i = 2; i < number; i++) {
if (number % i == 0) {
return false;
}
}
return true;
}
}
There was no need to start your counter at 0 and it mathematically wrong to start with number 2 ! Just begin with order and currentNumber initialized at 1 and if first prime number is what your user is looking for, no loop will be required !
Also, your loop condition after correct variable initialization was corrected from "<=" to "<".
That's all !
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 numbers? 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