I wrote the following program which displays if a number is a prime and if not a prime it display its prime factors and the next prime number.
However, I am not sure how to have the program ask the user if he/she wishes to input another number.
The user must answer either yes, no, y or n using any combination of lower and upper case letters.
If an invalid answer is given, the program must be informed that the answer was not acceptable, and then be prompted again for another answer. The program will only prompt up to three tries otherwise the program will exit.
If the answer is Yes (in any allowed form), the program must continue from step in the main function.
The program is written in prototype methods because that is what is called for.
If anyone can assist a newbie with the last part, i would greatly appreciate it.
code:
package primefactors;
import java.util.Scanner;
public class Primefactors {
//------------------three tries check method-------------------
public static int getNumberWithThreeTries(int m) {
int count = 1;
int number;
String s = "tries";
while (count <= 3) {
number = getInputNumber(m); //getScore returns -1 for invalid inputs
if (number <= 1) {
if ((3 - count) < 2) {
s = "try"; //just make sure that singular /plural form in the next statme is correct
}
if (count == 3) {
System.out.println("No more tries remaining!\n");
} else {
System.out.println((3 - count) + " " + s + " remaining! Try Again! \n");
}
count = count + 1;
} else {
return number;
}
}
return -1;
}
//-------------------boolean try again---work in progress---------------
public boolean askRunAgain() {
System.out.println("Would u like to solve more problems? ");
Scanner scanner = new Scanner(System.in);
boolean askRunAgain = scanner.nextBoolean();
return askRunAgain;
}
//----------------------------------boolen prime check method------------------
public static boolean isPrime(int m) {
for (int i = 2; i * i <= m; i++) {
if (m % i == 0) {
return false;
}
}
return true;
}
//------------------------next prime method-----------------
private static int nextPrime(int m) {
if (m % 2 == 0) {
m = m + 1;
}
for (m = m; !isPrime(m); m = m + 2)
;
return m;
}
//---------------------primefactors----------------------
public static String getPrimeFactors(int m) {
String ans = "";
for (int i = 2; i <= m; i = i + 1) {
if (m % i == 0) {
ans += i + "*";
m = (m / i);
i--;
}
}
return (ans.substring(0, ans.length() - 1));
}
//----------------------------------------------------------
public static int getInputNumber(int m) {
Scanner n = new Scanner(System.in);
int number = 0;
System.out.println("Enter an Integer greater than 1");
if (!n.hasNextInt()) {
System.out.print("That's not a number! you have ");
n.next();
return -1;
}
number = n.nextInt();
if (number <= 1) {
return -1;
}
return number;
}
//------------------------------main method ----------------------
public static void main(String[] args) {
int number;
int count = 0;
number = getNumberWithThreeTries(1);
if (number <= 1) {
System.out.println("Program Terminated");
System.exit(0);
}
if (isPrime(number)) {
System.out.println(number + ": Is a Prime Number \n\n"
+ getPrimeFactors(number) + ": Is its prime factor");
} else {
System.out.println(number + " Is not a Prime number\n\n"
+ getPrimeFactors(number) + " Are its prime factors \n\n"
+ nextPrime(number) + " Is the next Prime number\n ");
}
}
}
You need to place the getNumberWithThreeTries within a while loop, which at the end, ask if the user wants to try again. If they say yes, then your while loop should then continue to execute again, otherwise, it should exit.
Related
public class Car {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n = in.nextInt();
System.out.println(n+"!="+factorial(n));
}
public static int factorial(int num) {
return (num == 0) ? 1 : num * factorial (num - 1);
}
}
how make this code to text in console 3! = 1*2*3 = 6?
Don't use recursion for this. Besides, it isn't really efficient or necessary.
Scanner in = new Scanner(System.in);
int n = in.nextInt();
int fact = 1;
String s = n + "! = 1";
for (int i = 2; i <= n; i++) {
fact *= i;
s += "*" + i;
}
s += " = ";
System.out.println(s + fact);
There can be many ways to do it e.g. you can build the required string or print the trail while calculating the factorial. In the following example, I have done the former.
As an aside, you should check the input whether it is a positive integer.
import java.util.Scanner;
public class Car {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.print("Enter a positive integer: ");
int n = in.nextInt();
if (n >= 0) {
StringBuilder strFact = new StringBuilder();
int fact = factorial(n, strFact);
if (strFact.length() > 0) {
// Delete the last '*'
strFact.deleteCharAt(strFact.length() - 1);
System.out.println(n + "!= " + strFact + " = " + fact);
} else {
System.out.println(n + "!= " + fact);
}
} else {
System.out.println("This is an invalid input.");
}
}
public static int factorial(int num, StringBuilder strFact) {
int fact;
if (num == 0) {
fact = 1;
} else {
fact = num * factorial(num - 1, strFact);
strFact.append(num + "*");
}
return fact;
}
}
A sample run:
Enter an integer: 3
3!= 1*2*3 = 6
Original: So for my intro to programming class, we have to find the prime factors of a range of numbers that the user inputs (i.e. 59-65). The issue with a lot of the solutions here is that they use things that we haven't discussed in class like arrays, continue, etc. It's a pretty basic class. As for the requirements, we have to use a primeFact method/function that we call in the first for loop. She instructed us to use a while and for loop in the method to get the prime factors but everytime I think I have something, it doesn't come out right. Any help is really appreciated and my code is below. I really only need help with the method portion with the algorithm for finding the factors.
Edit: Here is the final solution that I turned in. It works and will give all prime factors of all numbers in a given range of numbers.
import java.util.Scanner;
public class PrimeFact {
public static void main(String[] args) {
int start, stop;
//Get input
Scanner input = new Scanner(System.in);
System.out.println("Please enter then two values with the lower value first");
start = input.nextInt();
stop = input.nextInt();
input.close();
//Displays for the start of the loop
System.out.println("Starting value (at least two digits): "+start);
System.out.println("Ending value (at least two digits): "+stop);
System.out.println("Prime factors for numbers between "+start+" and "+stop);
//Loop for the prime factors
for (int num = start; num <= stop; num++) {
primeFact(num);
}
}
// Method for Prime Factoring
public static void primeFact(int num) {
int divisor = 2;
System.out.print(num+" = ");
while (num>1) {
if ((num%divisor) == 0) {
System.out.print(divisor+" x ");
num=num/divisor;
} else {
divisor++;
}
}
System.out.print("1");
System.out.println();
}
}
public static void primeFact(int num) {
System.out.print(num+" = ");
for(int i=2;i<num;i++)
{
if(num%i==0)
{
if(isPrime(i))
{
System.out.println("Prime Factor for "+num+" is:"+i);
}
}
}
if(num==2)
System.out.println("Prime Factor for "+num+" is:"+num);
}
static boolean isPrime(int num){
for(int i=2;i<num;i++)
{
if(num%i==0)
{
return false;
}
}
return true;
}
//if u want use while replace the for loop like
public static void primeFact(int num) {
System.out.print(num+" = ");
int i=2;
while(i<num)
{
if(num%i==0)
{
if(isPrime(i))
{
System.out.println("Prime Factor for "+num+" is:"+i);
}
}
i=i+1;
}
if(num==2)
System.out.println("Prime Factor for "+num+" is:"+num);
}
static boolean isPrime(int num){
int i=2;
while(i<num)
{
if(num%i==0)
{
return false;
}
i=i+1;
}
return true;
}
you're method is pretty close to a solution. but your while loop is invalid.
remember it should be like this:
while(<boolean statement>){
//code here
}
I will reference the variable we are checking "primality" for as "num"
here's how to check for factors with a while loop:
//remember, num is given to us in the parameters of primeFact(int num).
boolean isPrime = true; //we are optimistic.
//we start at 2 because everything is divisible by one
int posFact = 2; //short for "possible factor"
while(posFact < num){ //this will start at 2, and go to 1 less than num
if(num % posFact == 0){ // "%" gives us remainder
isPrime = false; // we now know it's not prime
System.out.println("The number " + posFact + " is a factor of " + num + ".");
}
posFact++; //increments posFact up by 1
}
if(isPrime){ //This will only be true if the number is prime
System.out.println("The number " + num + " is prime!");
}
We can do the exact same thing with a for loop:
//remember, num is given to us in the parameters.
boolean isPrime = true; //we are optimistic.
for(int posFact = 2; posFact < num; posFact++){ //posFact's initialization and incrementation was moved here.
if(num % posFact == 0){ // "%" gives us remainder
isPrime = false; // we now know it's not prime
System.out.println("The number " + posFact + " is a factor of " + num + ".");
}
}
if(isPrime){ //This will only be true if the number is prime
System.out.println("The number " + num + " is prime!");
}
I'm still fairly new in java programming and I've gotten some aspects down but the classes within Java are by far giving me the most trouble. What I'm trying to do is make a random number game where the player has to pick a number 1 through 10 and if it's wrong then try again and have the program record how many times they guessed (but not add to the number of guess when a number has been picked previously or if the number that was picked is outside the specified range) I have already worked out the logic code and was trying to make a class specifically for just the logic and a class that is specifically just for the I/O interface. But I'm having one heck of a time. Any input or tips will be very appreciated and I will provide the code that I already have below:
This is the Logic class where I want it to handle all the logic
package guessapp;
import java.util.HashSet;
import java.util.Scanner;
public class GuessLogic {
public static int Logic() {
HashSet<Integer> hs = new HashSet<>();
int GuessLogic = (int) (Math.random() * 10 + 1);
Scanner keyboard = new Scanner(System.in);
int A;
int guess;
int NumGuess = 1;
do {
guess = keyboard.nextInt();
if (hs.contains(guess)) {
A = 1;
return A;
}
if (guess < 0 || guess > 10) {
A = 2;
return A;
}
if (guess == GuessLogic) {
A = 3;
return A; // this will stop the loop
} else if (guess < GuessLogic) {
NumGuess++;
A = 4;
return A;
} else if (guess > GuessLogic) {
NumGuess++;
A = 5;
return A;
}
hs.add(guess);
} while (true);
}
public static int getGuess() {
int guess;
Scanner keyboard = new Scanner(System.in);
guess = keyboard.nextInt();
return guess;
}
}
And this is the class I want to handle all I/O interface
import java.util.HashSet;
import java.util.Scanner;
public class GuessApp {
public static void main(String[] args) {
int r, w, y;
r = GuessLogic.Logic();
w = GuessLogic.getGuess();
int NumGuess;
NumGuess = 2;
System.out.print("Enter a guess: ");
if (r == 1) {
System.out.println("You have already entered this number");
}
if (r == 2) {
System.out.println("Your guess is out of the specified range. Please try again.");
}
System.out.println("Your guess is " + w);
if (r == 3) {
System.out.println("You got it right!! Congrats!! Total Number of Guesses: " + NumGuess);
} else if (r == 4) {
System.out.println("You are wrong!!! Hint: Guess Higher, Guess number: " + NumGuess);
} else if (r == 5) {
System.out.println("You are wrong!!! Hint: Guess Lower, Guess number: " + NumGuess);
}
}
}
Below is the modified codes. There are some general ideas:
GuessLogic should be used as an instance rather than a static class. Because you need GuessLogic to save the operations and the target number.
The while loop should be coded in main. Because GuessLogic is responsible for logic only.
The elements is Set is unique, so there is no need to count how many different number by yourself.
GuessApp:
public class GuessApp {
public static void main(String[] args) {
int r, w, y;
GuessLogic guessLogic = new GuessLogic();
while(true){
System.out.print("Enter a guess: ");
w = guessLogic.getGuess();
r = guessLogic.Logic();
if (r == 1) {
System.out.println("You have already entered this number");
continue;
}
if (r == 2) {
System.out.println("Your guess is out of the specified range. Please try again.");
continue;
}
System.out.println("Your guess is " + w);
if (r == 3) {
System.out.println("You got it right!! Congrats!! Total Number of Guesses: " + guessLogic.getNumber());
break;
} else if (r == 4) {
System.out.println("You are wrong!!! Hint: Guess Higher, Guess number: " + guessLogic.getNumber());
} else if (r == 5) {
System.out.println("You are wrong!!! Hint: Guess Lower, Guess number: " + guessLogic.getNumber());
}
}
}
}
GuessLogic:
public class GuessLogic {
HashSet<Integer> hs = new HashSet<>();
int number = (int) (Math.random() * 10 + 1);
public int getNumber(){
return hs.size();
}
public int Logic(int guess) {
if (hs.contains(guess)) {
return 1;
}
if (guess < 0 || guess > 10) {
return 2;
}
if (guess == number) {
return 3; // this will stop the loop
} else if (guess < number) {
// just add to the set. The set will guarantee that there is no repetitive item.
hs.add(guess);
return 4;
} else if (guess > number) {
hs.add(guess);
return 5;
}
return -1;
}
public int getGuess() {
int guess;
Scanner keyboard = new Scanner(System.in);
guess = keyboard.nextInt();
return guess;
}
}
In this problem, I need to ask the user to input the number of integers they will put in. Then, they will manually input each number. Finally, the program counts the sum and max of all even inputs.
I am having trouble with initiating the value. If I set them to zero, there would be an issue if all the numbers were negative even numbers.
import java.util.*;
public class Exercise07 {
public static void main(String[] args) {
Scanner thing = new Scanner(System.in);
evenSumMax(thing);
}
private static void evenSumMax(Scanner stuff) {
System.out.print("How many integers?");
int times = stuff.nextInt();
int evenSum = 0;
int evenMax = 0;
System.out.println("Number 1 : ");
int value = stuff.nextInt();
if (value % 2 == 0) {
evenSum += value;
evenMax = value;
}
for (int i = 2 ; i <= times; i++) {
System.out.print("Number " + i + " : ");
value = stuff.nextInt();
if (value % 2 == 0) { // if even
evenSum += value;
if (evenMax < value) {
evenMax = value;
}
}
}
System.out.println("Even sum = " + evenSum + ", even max = " + evenMax);
}
}
Set evenMax to the minimum possible number Integer.MIN_VALUE
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 !