I'm trying to figure out how to create a java program where the user inputs a series of integers, the last integer being a 0 (when the program should stop). After stopping, the program should print out the sum of the integers. This needs to be done using a while (true) loop with an if statement
if (num == 0) {
break;
}
With everything I have tried so far, the loop will not stop even when 0 is inputted.
1) Declare a sum variable
2) Start a infinite loop
3) Read user input
4) Add it to sum variable
5) If the user input is 0 break out of the loop and print the value of sum.
import java.util.Scanner;
public class Statictest {
public static void main(String[] args) {
int sum = 0;
Scanner scn = new Scanner(System.in);
while (true) {
int temp = scn.nextInt();
if (temp == 0) {
break;
}
sum += temp;
}
System.out.println("Sum: " + sum);
}
}
Related
After writing 1 on scanner I want a random dice number generated and after pressing 1 again I want another random number generated but now I want it added with previous number. I want to make a loop, I want to keep pressing 1 and keep adding random numbers till I reach a certain number.
Thank you.
import java.util.Random;
import java.util.Scanner;
public class dice {
public static void main(String[] args) {
// TODO Auto-generated method stub
for (int k = 0; k < 100; k++) {
Scanner scan = new Scanner(System.in);
int s = scan.nextInt();
System.out.println(s);
int previous = s;
if (s == 1) {
Random ran = new Random();
int n = ran.nextInt(6) + 1;
System.out.print(n);
int next;
while (true) {
next = scan.nextInt();
if (next == 1) {
System.out.println(previous);
}
previous = n + 10;
}
}
}
}
}
Define previous outside the for loop, and replace
int previous = s;
previous = n + 10;
with
previous += s;
previous += n + 10;
Scanner sc=new Scanner(System.in);
int sum=0;
for(;;)
{
if(sc.nextInt()==1)
{
int num = (int)(Math.random()*6); // using the pre-defined random function in java.lang.Math class
System.out.println("Dice Value: "+num);
sum+=num; // shorthand adding the number for each iteration
}
//if(sum>100)
// break;
//if statement to check if value of sum is greater/lesser than a specific number
}
System.out.println("Final Answer: "+sum)
Something like this might work (not yet tested): an infinite loop that can be terminated as per choice.
If you are looking for a way that the program works as soon as you physically press the '1' key on your keyboard, without having to press the enter key, something like a keyevent might work:
https://docs.oracle.com/javase/7/docs/api/java/awt/event/KeyEvent.html
Please do let me know if there are any errors or doubts :)
Here is my program which is supposed to create an array and initialize prime numbers to it. The prime numbers should then be printed but the program just keeps running.
import java.util.*;
public class primes
{
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
System.out.println("Enter number of primes ");
int x = scan.nextInt();
int[] prime = new int[x];
int div=2,hold=2;
int c=0;
while (prime[x-1]==0)
{
for(int a=2; div>a;a++)
{
if(div>a && div%a==0)
a=div;
else if(div==(a-1))
hold=div;
}
if(div==2||hold!=prime[c-1])
{
prime[c]=hold;
c++;
}
div++;
}
for(int f =0; f<x;f++)
System.out.print(" "+prime[f]+" ");
}
}
I tried changing my loops but I just don't know whats wrong
Like the others mentioned your logic is not right, try something like:
public static void main(String args[]) {
Scanner scan = new Scanner(System.in);
System.out.println("Enter number of primes ");
int x = scan.nextInt();
List<Integer> primes = getPrimes(x);
Integer[] primeArray = primes.toArray(new Integer[primes.size()]);
for(int i :primes.toArray(primeArray)){ // you could just use for(int i :primes){ if you don't need array
System.out.print(i + " ");
}
}
private static List<Integer> getPrimes(int upperLimit) {
ArrayList primes = new ArrayList();
for (int i = 2; i < upperLimit; i++) {
boolean isPrime = true;
// Is it prime?
for (int j = 2; j < i; j++) {
if (i % j == 0) {
isPrime = false;
break;
}
}
if (isPrime)
primes.add(i);
}
return primes;
}
The above will print out up to the numbers entered so if you type 5 it will print out 2 3 but not 5.
The following is an other example with Java 8, this one will print as many prime numbers based on the input, if you input 5 you will get 2 3 5 7 11
public static void main(String args[]) {
Scanner scan = new Scanner(System.in);
System.out.println("Enter number of primes ");
int x = scan.nextInt();
long[] prime = primes(x).toArray();
Arrays.stream(prime).forEach(value -> System.out.print(value + " " ));
}
private static LongStream primes(long max) {
return LongStream.iterate(2, i -> i + 1)
.filter(PrimeNumber::isPrime)
.limit(max);
}
private static boolean isPrime(long x) {
return LongStream.rangeClosed(2, (long)(Math.sqrt(x)))
.allMatch(n -> x % n != 0);
}
Your code is wrong. First correct it, And i think you want to store prime numbers coming in range of 1 to N where N is user provided number. Use arrayList (growable) to store it.
It will keep on running because you have this: while (prime[x-1]==0). Where x is an input from the user. Say 5 for instance, then prime[5-1] initially is going to contain a 0 always, and you are running your while loop on this condition which is always going to turn true, thus never ending. Also, your prime number generation logic is not right!
I ran your code in debugger mode and I found the problem.
I tested your program with x=5.
At the end of the first while loop iteration you have :
prime[0] = 2
div = 3
hold = 2
c = 1
And here's the problem :
if(div==2||hold!=prime[c-1])
{
prime[c]=hold;
c++;
}
This part won't ever be reached anymore because :
div is never decrement, so it will always be superior to 2.
hold is
equal to prime[c-1], and never change value.
So prime will always stick to be : 2 0 0 0 0, and your while loop will never end.
I found what was wrong and rewrote the code, it works now. The program asks the user for the number primes they want to see and it prints them after storing them in a basic integer array.
import java.util.*;
public class Prime
{
public static void main(String [] args)
{
Scanner scan= new Scanner(System.in);
int i=0, hold=2, d=2;
boolean flag = true;
System.out.println("Enter the number of primes.");
int[] prime= new int[scan.nextInt()];
for(;flag;){
for(int a=2;d>a;a++){
if(d==(a)||d%a==0){
break;
}
if((d-1)==a){
hold = d;
}
}
d++;
if(hold==2 || hold!=prime[i-1]){
prime[i] = hold;
i++;
}
if(i==prime.length)
flag= false;
}
for(int x=0;x<prime.length;x++)
System.out.print(prime[x]+" ");
System.out.println("");
}
}
I'm a noob programmer, but I've been stuck on this one bit of code. How do you recurse back to start? I've tried several different methods but they all either take a ridiculous amount of code or don't work properly. I've been trying to implement this "simple" piece of code in all of my programming assignments, but it hasn't been working out. Thanks!
p.s. I've already finished the assignment. I'm just trying to make it more "complete".
public class OddProduct {
public static void main(String[] args) {
//Inputs from user
System.out.println("Enter an odd number");
Scanner input_odd = new Scanner(System.in);
int odd = input_odd.nextInt();
int oddproduct = 1;
//Multiplies all odd integers
for (int counter = 1; counter <= odd; counter = counter + 2){
oddproduct = oddproduct * counter;
}//end of for- loop
System.out.printf("\nThe product of all the odd integers up to %d is %d\n",
odd, oddproduct);
/* MY NOTES FOR RECURSE
if (odd%2 == 1){ proceed normally}
else if (odd%2 != 1) { HOW TO LOOP BACK???}
else { println = "Application closed"}
*/
}//end of main method
}//end of OddProduct class
Based upon your Notes I think this is what you require
Scanner input_odd = new Scanner(System.in);
int odd = 0;
while (odd % 2 != 1) { // fails first time && if user enters even number
System.out.println("Enter an odd number");
odd = input_odd.nextInt();
}
I'm doing an online course by the name of "Object-Oriented programming with Java"
And I can't figure out exercise 36..
Create a program that asks the user to input numbers (integers). The program prints "Type numbers” until the user types the number -1. When the user types the number -1, the program prints "Thank you and see you later!" and the sum of the numbers entered by the user (without the number -1).
import java.util.Scanner;
public class LoopsEndingRemembering {
public static void main(String[] args) {
Scanner reader = new Scanner(System.in);
int n = 0;
int sum = 0;
while (n != -1) {
System.out.println("Type numbers");
n = Integer.parseInt(reader.nextLine());
sum = sum + n; // <-- The value set here is tossed once the loop of over?..
}
System.out.println("Thank you and see you later!");
System.out.println("The sum is " + sum); // <-- Does not acknowledge the free state of 'loop' and any variables that come of it
}
}
So when I click the 'Run tests locally' (it's a plugin
button) in Netbeans I'm getting:
With input 1 -1 you should print "the sum is 1" expected:<1> but was:<0>
The '0', to my understanding, is indicating that the last println only recognizes the initialization of 'sum'..why is that?..
Change you while loop to check the users input as the last thing in the loop. Example:
public static void loopTest()
{
Scanner reader = new Scanner(System.in);
int n = 0;
int sum = 0;
System.out.println("Type a number then press enter... type '-1' to sum the numbers and exit");
n = Integer.parseInt(reader.nextLine());
while (n != -1)
{
sum = sum + n;
n = Integer.parseInt(reader.nextLine());
}
System.out.println("Thank you and see you later!");
System.out.println("The sum is " + sum ); // <-- Does
}
I am have a program which prints off the fibonacci sequence up to a given input. The user puts in a number and it prints out the sequence up to that many numbers.
ex: input = 4 prints 1 1 2 3
I want to limit the program to only allowing an input 1-16. The way I have it now will print the sequence an then prints the error message? Any suggestions? Thank you
public class FibonacciGenerator
{
private int fibonacci = 1;
public FibonacciGenerator()
{
}
public int Fibonacci(int number)
{
if(number == 1 || number == 2)
{
return 1;
}
else if (number > 16)
{
System.out.println("Error must select 1-16");
}
else
{
int fib1=1, fib2=1;
for(int count= 3; count < 17 && count <= number; count++)
{
fibonacci = fib1 + fib2;
fib1 = fib2;
fib2 = fibonacci;
}
}
return fibonacci;
}
}
Here is my main method:
import java.util.Scanner;
public class FibonacciPrinter
{
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);
System.out.print("Enter an integer 1-16: ");
int input = in.nextInt();
FibonacciGenerator newNumber = new FibonacciGenerator();
System.out.println("Fibonacci sequence up to " + input + " places.");
for(int fibCount = 1; fibCount <= input; fibCount++)
{
int sequence = newNumber.Fibonacci(fibCount);
System.out.print(sequence);
}
}
}
As a recommendation don't make your methods or variables start with capital letter, capital letter is used by convention for Classes only.
Also, you should validate input variable before passing it to your method.
I mean:
if (input > 16 || input < 1) {
System.out.println("Enter a number between 1-16");
}
else {
for(int fibCount = 1; fibCount <= input; fibCount++)
{
int sequence = newNumber.Fibonacci(fibCount);
System.out.print(sequence);
}
}
In your Fibonacci function, your first line should be an if statement to see if the number is greater than 16. If it is, then you can throw an error.
Below is what it should be:
public int Fibonacci(int number) {
if (number > 16 || number < 1) throw new IllegalArgumentException("Error. Must select 1-16.");
// Rest of the code
}
In your Fibonacci function, for number not equal to 1 and 2. The return statement return fibonacci; will always be called. That's why the error message is printed with the sequence.
To avoid this, you can use #Frakcool method to validate variable input before passing it to Fibonacci function. Alternatively, you may use do-while loop to do this (force the user to retry).
do{
System.out.print("Enter an integer 1-16: ");
input = in.nextInt();
if (input<1 || input>16)
System.out.println("Error. Must select within 1-16.");
}while(input<1 || input>FibonacciGenerator.upper_limit);
Some other suggestion:
Make your methods and variables name start with a lower case letter
To avoid repeat calculation (for-loop in Fibonacci method), use integer array to store the fibonacci values and pass integer array instead of integer (for small input number such as 16). Another way is to set two more global variables to store the last and second last calculated values.
Make upper limit (and/or lower limit) as a global variable for better maintenance
public static int upper_limit = 16;
and get it in other class as
FibonacciGenerator.upper_limit