a super silly question but why does the method prime recurse infinitely ?
this is a simple java code where i'm trying to make a method i can call to get the prime of parameter x , but it tells me that the method will recurse infinitely , i tried copy pasting the code of the prime method to the main method and it worked well , so can someone help please?
`
import java.util.*;
public class Mavenproject2 {
static int prime(int x) {
boolean f = true;
if (x == 1 || x == 0) {
f = false;
} else {
for (int i = 2; i < x; i++) {
if (x % i == 0) {
f = false;
break;
}
}
}
if (f) {
System.out.println("prime");
} else {
System.out.println("not prime");
}
return prime(x);
}
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("enter number");
int x = input.nextInt();
System.out.println(prime(x));
}
}
`
If you just want to know if the number passed in is prime. You need to change your return type to a bool and return f.
You're returning prime(x) which will keep calling into itself.
I would actually do something like this
import java.util.*;
public class Mavenproject2 {
static string prime(int x) {
boolean f = true;
if (x == 1 || x == 0) {
f = false;
} else {
for (int i = 2; i < x; i++) {
if (x % i == 0) {
f = false;
break;
}
}
}
if (f) {
return "prime";
}
return "not prime";
}
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("enter number");
int x = input.nextInt();
System.out.println(prime(x));
}
}
Related
I would like to apologise in advance if im doing something wrong with the code formatting because this is my second time posting here
I have a java assignment due in a couple of days in which the user enters a string and only the integers are collected from it and placed in the array intArray
Now i think i got the logic right in the code below but when i run it in the main, it asks for the string and the boolean, when i enter both it gives me the error
"Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 115"
This is what i entered for example
"Enter a string and true if you want to skip errors or false if you want to skip errors
sdak23
false"
this is my main:
import java.util.Scanner;
public class MainStringToIntArray {
public static void main(String[] args) {
Scanner intut = new Scanner(System.in);
Scanner input = new Scanner(System.in);
StringToIntArray s1 = new StringToIntArray();
System.out.println("Enter a string and true if you want to skip errors or false if you want to skip errors");
s1.scanStringToIntArray(intut.next(), input.nextBoolean());
}
}
import java.util.Arrays;
import java.util.Scanner;
public class StringToIntArray {
private int[] intArray = new int[10];
public StringToIntArray() {
Arrays.fill(intArray, Integer.MIN_VALUE);
}
public int indexOf(int intToFind) {
int b = 0;
for (int a = 0; a < intArray.length; a++) {
if (intArray[a] == intToFind) {
b = intArray[a];
}
else {
b = -1;
}
}
return b;
}
public int indexOf(String intToFind) {
int b = 0;
for (int a = 0; a < intArray.length; a++) {
if (intArray[a] == Integer.parseInt(intToFind)) {
b = intArray[a];
}
else {
b = -1;
}
}
return b;
}
public boolean contains(int intToFind) {
int a = indexOf(intToFind);
if (a > 0) {
return true;
}
else {
return false;
}
}
public boolean contains(String intToFind) {
int a = indexOf(intToFind);
if (a > 0) {
return true;
}
else {
return false;
}
}
public int get(int index) {
if(index < 0 && index > 10) {
return Integer.MIN_VALUE;
}
else {
return intArray[index];
}
}
public boolean scanStringToIntArray(String s, Boolean skipErrors) {
Boolean result = null;
Scanner input = new Scanner(s);
int l = s.length();
if ((skipErrors)) {
String discard = null;
for (int a = 0; a < l; a++) {
for (int z = 0; z < l; z++) {
if (input.hasNextInt(s.charAt(z))) {
intArray[a] = s.charAt(z);
System.out.println(a);
result = true;
}
else {
discard = discard + s.charAt(z);
}
}
}
}
else {
for (int v = 0; v < l; v++) {
for (int p = 0; p < l; p++) {
if ((input.hasNextInt(s.charAt(p)))) {
intArray[v] = s.charAt(p);
System.out.println(v);
}
else {
System.out.println(v);
result = false;
}
}
}
}
return result;
}
}
The issue is in the get method. It is logically impossible for the index to be both less than 0 and greater than 10; you probably want to use the logical or operator (||). Also, the maximum index of the array is actually 9, as arrays are zero indexed.
public int get(int index) {
if(index < 0 || index > 9) {
return Integer.MIN_VALUE;
}
else {
return intArray[index];
}
}
There are other logical errors in your code as well. All your indexOf methods should be returning the index where the element was first found instead of the element itself and your else branch is always resetting it to -1 each time it is not found.
I am trying to find palindrome no but every time it is showing false for every no even for 121
please Help....
public boolean isPalindrome(int x) {
if(x<0 || x%10==0){
return false;
}
int rev = 0;
while(x!=0){
rev=(rev*10)+(x%10);
x/=10;
}
if(x==rev){
return true;
}
else{
return false;
}
}
enter image description here
As an option, you may create something like this:
public boolean isPalindrome(int x) {
StringBuilder sb = new StringBuilder();
sb.append(x);
return sb.toString().equals(sb.reverse().toString());
}
Because after your while loop ends, x will be 0, you have to act on a copy instead
public boolean isPalindrome(int x) {
int num = x;
if(x<0 || x%10==0){
return false;
}
int rev = 0;
while(x!=0){
rev=(rev*10)+(x%10);
x/=10;
}
if(num==rev){
return true;
}
else{
return false;
}
}
All you need to do is build the new number as you reduce the original. Then compare the two.
for (int i : new int[]{121,12321, 123,34543,20012}) {
System.out.printf("%6d - %s%n", i, isPalindrome(i));
}
public static boolean isPalindrome(int numb) {
int n = 0;
for (int b = numb; b > 0;) {
n *= 10;
n += b%10;
b/=10;
}
return n == numb;
}
Prints
121 - true
12321 - true
123 - false
34543 - true
20012 - false
Hope this is useful:
public static boolean palindrome(int n) {
int nPalindrome = 0;
int nCopy = n;
while (n != 0) {
nPalindrome = nPalindrome *10 + n % 10;
n = n / 10;
}
if (nCopy == nPalindrom) {
return true;
} else {
return false;
}
}
You function can be as simple as below
public static void main(String args[]){
int r,sum=0;
int n=454;//It is the number variable to be checked for palindrome
if(isPalindrome(n)) {
System.out.println("palindrome number ");
} else {
System.out.println("not palindrome number ");
}
}
public boolean isPalindrome(int n) {
while(n>0){
r=n%10; //getting remainder
sum=(sum*10)+r;
n=n/10;
}
return n==sum;
}
I had static method which is to find out prime number and it is working fine but the same method i am trying to keep inside main method it is throwing errors by stating illegal modifiers for parameter and void method does not return value
the same code is working fine outside of main method, any one plz sugggest me why it is not working in main() . Thanks ..!!
My method
public static boolean isPrimeNumber(int number) {
if (number == 2 || number == 3) {
return true;
}
if (number % 2 == 0) {
return false;
}
int sqrt = (int) Math.sqrt(number) + 1;
for (int i = 3; i < sqrt; i += 2) {
if (number % i == 0) {
return false;
}
}
return true;
}
Inside main() with lot of error message
inside main
Solution
Thanks Logan --- need to add methods outside main method
my working code is added below
public class Squar {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int num = scan.nextInt();
Squar s = new Squar();
//System.out.println(s.isPrime(num));
scan.close();
System.out.println("M2 "+s.isPrimeNumber(num));
}
public boolean isPrimeNumber(int number) {
if (number == 2 || number == 3) {
return true;
}
if (number % 2 == 0) {
return false;
}
int sqrt = (int) Math.sqrt(number) + 1;
for (int i = 3; i < sqrt; i += 2) {
if (number % i == 0) {
return false;
}
}
return true;
}
}
You are getting this error because Java does not support nested function.
You are implementing method inside other method, that is not possible. to nest methods use lambdas in java 8.
have a look at Can methods in java be nested and what is the effect? [closed]
So in a few words i made a class extending the RandomGenerator to randomly giving back PRIME, POWER OF 2(2,4,8,16,32,64,128 etc) , FIBONACCI AND SQUARE NUMBERS (1,4,9,16,25,36 etc). Then i made a simple program to call my class and giving back random numbers while the user defines the space (1,n). Both programs compile just fine. My problem is that when i run the program it always returns 0 for each value. I'm new to java. Can anyone help me?
import acm.util.*;
public class RandomGeneratorImproved2 extends RandomGenerator
{
private int i,j,a,c,d,e,temp,n,Pnumber,Fnumber,number2,numbersq;
private long b;
boolean flag,flag2,flag3,flag4,flag5;
private double temp1;
public RandomGeneratorImproved2 (int n)
{
this.n = n;
}
public void nextPrime(int n) // PRIME NUMBERS
{
Pnumber = rgen.nextInt(1, n);
i=2;
flag2 = false;
if ( Pnumber == 1 ) // Check for value 1 cause it cannot check it inside the loop
{
flag2=true;
}
while ( (i<n) && (flag2 == false) )
{
flag = true;
j=2;
do
{
a = i%j;
if ( (a == 0) && (i != j) )
{
flag = false;
}
if (i!=j-1)
{
j = j+1;
}
} while ( j<i );
if ((flag == true) && (Pnumber==i)) //
{
flag2 = true;
}
if ((i==99) && (flag2==false)) // restart if the number is not prime
{
i = 1;
Pnumber = rgen.nextInt(1, n);
}
i = i + 1;
}
}
public int getPrime() //POWER OF 2 NUMBERS
{
return Pnumber;
}
public void nextPowerof2(int n)
{
number2 = rgen.nextInt(1, n);
i=1;
b=2;
flag3 = false;
while ( i<n ) // n <= 31
{
if (number2 == b)
{
flag3 = true;
}
b = 2*b;
if ((i == n-1) && (flag3==false))
{
i=1;
number2 = rgen.nextInt(1,n);
b=2;
}
i=i+1;
}
}
public int getPowerof2()
{
return number2;
}
public void nextFibonacciNumber(int n) // FIBONACCI NUMBERS
{
Fnumber = rgen.nextInt(1, n);
c=0;
d=1;
flag4 = false;
i=1;
while ( i<n && flag4==false )
{
temp = d;
d = d + c;
c = temp;
i=i+1;
if (Fnumber == d)
{
flag4 = true;
}
if ((flag4 == false) && (i==n))
{
i=1;
c=0;
d=1;
Fnumber = rgen.nextInt(1, n);
}
}
}
public int getFibonacciNumber()
{
return Fnumber;
}
public void setSquareNumber(int n) // SQUARE NUMBERS
{
numbersq = rgen.nextInt(1, n);
flag5 = false;
i=1;
temp1 = Math.sqrt(n);
while ( i<temp1 && flag5 == false )
{
e = i*i;
i = i + 1;
if ( numbersq == e )
{
flag5 = true;
}
if ( i == 20 && flag5 == false )
{
i=1;
numbersq = rgen.nextInt(1, n);
}
}
}
public int getSquareNumber()
{
return numbersq;
}
public String toString()
{
return "Your Prime number is : " + Pnumber + "\nYour Power of 2 number is : " + number2 + "\nYour Fibonacci number is : " + Fnumber + "\nYour square number is : " + numbersq;
}
private RandomGenerator rgen = RandomGenerator.getInstance();
}
import acm.program.*;
public class caller2 extends Program
{
public void run()
{
int n = readInt("Please give me an integer to define the space that i'll look for numbers : ");
RandomGeneratorImproved2 r1 = new RandomGeneratorImproved2(n);
println(r1);
}
}
As stated you've only defined those method. You never call any of the methods that are setting those values so all are still in their initialized state. Try adding the following to the constructor after setting n;
nextPrime(n);
nextFibonaccitNumber(n);
nextPowerof2(n);
I have to create the yahtzee game and its methods like full house, small straight, big straight, 3 of kind, 4 of kind , and chance. Now this is what i have done so far and i would like to know if my methods are right and also i'm having a hard time trying to figure out how to check if its yahtzee , 3 of kind, 4 of kind , etc and this is in my main method. The program consists of seven rolls, where every roll can have up to two sub-rolls
static final int NUM_RERROLS_ = 2;
static final int NUM_OF_DICE = 5;
static final int NUM_ROLLS_ = 7;
static final int[] dice = new int[NUM_OF_DICE];
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
rollDice();
for (int i = 0; i < NUM_RERROLS_; i++) {
if (gotYatzee()) {
break;
}
System.out.println(diceToString());
askUser();
System.out.println("Which dice do you want to reroll: ");
secondReroll(convert(keyboard.nextLine()));
}
System.out.println(diceToString());
if (gotYatzee()) {
System.out.println("You got Yatzee & 50 points!");
} else if (largeStraight() == true) {
System.out.println("You got large straight");
} else {
System.out.println("Sorry no large straight");
}
if (smallStraight() == true) {
System.out.println("You got smallStraight");
} else {
System.out.println("Sorry no small straight");
}
if (fullHouse() == true) {
System.out.println("You got full house");
} else {
System.out.println("Sorry no full house");
}
{
System.out.println("SORRY NO YAHTZEE");
}
if (askUser() == false) {
if (largeStraight() == true) {
System.out.println("You got large straight");
} else {
System.out.println("Sorry no large straight");
}
if (smallStraight() == true) {
System.out.println("You got smallStraight");
} else {
System.out.println("Sorry no small straight");
}
if (fullHouse() == true) {
System.out.println("You got full house");
} else {
System.out.println("Sorry no full house");
}
}
}
public static void rollDice() {
for (int i = 0; i < NUM_OF_DICE; i++) {
dice[i] = randomValue();
}
}
public static int randomValue() {
return (int) (Math.random() * 6 + 1);
}
public static String diceToString() {
String dado = "Here are your dice: ";
for (int element : dice) {
dado = dado + element + " ";
}
return dado;
}
public static boolean gotYatzee() {
for (int element : dice) {
if (element != dice[0]) {
return false;
}
}
return true;
}
public static void secondReroll(int[] newValue) {
for (int element : newValue) {
dice[element - 1] = randomValue();
}
}
public static int[] convert(String s) {
StringTokenizer st = new StringTokenizer(s);
int[] a = new int[st.countTokens()];
int i = 0;
while (st.hasMoreTokens()) {
a[i++] = Integer.parseInt(st.nextToken());
}
return a;
}
public static boolean Chance() {
for (int element : dice) {
int i = 0;
if (element != dice[i]) {
i++;
return false;
}
}
return true;
}
public static boolean smallStraight() {
for (int i = 1; i <= NUM_OF_DICE; i++) {
boolean b = false;
for (int j = 0; j < NUM_OF_DICE; j++) {
b = b || (dice[j] == i);
}
if (!b) {
return false;
}
}
return true;
}
public static boolean largeStraight() {
int[] i = new int[5];
i = dice;
sortArray(i);
if (((i[0] == 1) && (i[1] == 2) && (i[2] == 3) && (i[3] == 4) && (i[4] == 5))
|| ((i[0] == 2) && (i[1] == 3) && (i[2] == 4) && (i[3] == 5) && (i[4] == 6))
|| ((i[1] == 1) && (i[2] == 2) && (i[3] == 3) && (i[4] == 4) && (i[5] == 5))
|| ((i[1] == 2) && (i[2] == 3) && (i[3] == 4) && (i[4] == 5) && (i[5] == 6))) {
return true;
} else {
return false;
}
}
public static boolean askUser() {
Scanner keyboard = new Scanner(System.in);
int a = 0;
String yes = "Yes";
String no = "No";
System.out.println("Do you want to reroll the dice again: Yes or No? ");
String userInput;
userInput = keyboard.next();
if (userInput.equals(yes)) {
System.out.println("ALRIGHTY!!");
return true;
} else if (userInput.equals(no)) {
}
return false;
}
public static boolean threeKind() {
int[] a = new int[5];
a = dice;
sortArray(a);
if ((((a[0] == a[1]) && (a[1] == a[2])) // Three of a Kind
|| ((a[1] == a[2]) && ((a[2] == a[3])
|| (((a[2] == a[3]) && (a[3] == a[4]))))))) {
return true;
} else {
return false;
}
}
/*public static boolean fourKind(int[] dice) {
}
*/
public static int[] sortArray(int[] numbers) {
int stop;
for (stop = 0; stop < numbers.length; stop++) {
for (int i = 0; i < numbers.length - 1; i++) {
if (numbers[i] > numbers[i + 1]) {
swap(numbers, i, i + 1);
}
}
}
return numbers;
}
public static void swap(int[] numbers, int pos1, int pos2) {
int temp = numbers[pos1];
numbers[pos1] = numbers[pos2];
numbers[pos2] = temp;
}
public static boolean fullHouse() {
int[] a = new int[5];
a = dice;
sortArray(a);
if ((((a[0] == a[1]) && (a[1] == a[2])) && // Three of a Kind
(a[3] == a[4]) && // Two of a Kind
(a[2] != a[3]))
|| ((a[0] == a[1]) && // Two of a Kind
((a[2] == a[3]) && (a[3] == a[4])) && // Three of a Kind
(a[1] != a[2]))) {
return true;
} else {
return false;
}
}
}
basically i want to figure out a way to check if its full house, 3 of kind, 4 of kind , etc
You have 6 dice after three rolls. Sort the array of user-retained dice after the 3 rolls.
Yahtzee: ((die[0] == die[4]) || (die[1] == die[5]))
4 of a kind: ((die[0] == die[3]) || (die[1] == die[4] || (die[2] == die[5]))
Small straight, 3 tests (x = 3,4,5): ((die[x] - die[x-3]) == 3)
Large straight, 2 tests (x = 4,5): ((die[x] - die[x-4]) == 4)
etc.
Chance: Up to the user, right?
Unless I'm missing something (I'm a little rusty on Yatzee), this should be fairly straightforward.