CODEWITHSUNDEEP
javafor-loopinfinite-loop
Jake
Jake

Reputation: 73

Java number sequence loop

So hi i'm getting infinite loop problem i don't know whats wrong with my code i'm trying to make a number sequence format is at the bottom i think the problems are in my condition? 

import java.util.Scanner;
public class tester {
    public static void main(String[] args) {
        Scanner x = new Scanner(System.in);


        int n;         

        System.out.print("Enter how many numbers to display");
        n = x.nextInt();


        while(n!=0) {                     //is this right?
            for ( int i = 0; i<=n; i++) {
                if(i%2==0) {
                    n += 2;
                    System.out.print(n);

                } else {
                    n += 3;
                    System.out.print(n);
                }  
            }

        }
    }
}

Outputs i'm trying to get

Enter how many numbers to display : 5
1 3 6 8 11

2. 
Enter how many numbers to display : 16
1 3 6 8 11 13 16 18 21 23 26 28 31 33 36 38  //but im getting infinite loops

 // the sequence pattern is +2 then +3

Upvotes: 0

Views: 4875

Answers (5)

AJ.
AJ.

Reputation: 4534

Two problems:

int stop = n; // declare one local var to stop the for loop 

if (n != 0) { //switch to if condition
    for (int i = 0; i <= stop; i++) {  
      //loop's exit condition wasn't met because 'n' was also being incremented
        if (i % 2 == 0) {
            n += 2;
            System.out.print(n+" ");

        } else {
            n += 3;
            System.out.print(n+" ");
        }
    }     
}

Upvotes: 2

Jake
Jake

Reputation: 73

Based on your answers I found a solution that works:

int n;    

System.out.print("Enter how many numbers to display");
n = x.nextInt();
int k = -2; // so that it starts with 1 when i add +3
int stop = n-1;   

if(n!=0) {                     
    for ( int i = 0; i<=stop; i++) {
        if(i%2==0) {
            k += 3;
            System.out.print(k+" ");
        } else {
            k += 2;
            System.out.print(k+" ");
        }  
    }
}

Upvotes: 0

Tom Wellbrock
Tom Wellbrock

Reputation: 3042

You have to replace your while-loop with an if-condition like so:

import java.util.Scanner;
public class tester {
    public static void main(String[] args) {

        Scanner x = new Scanner(System.in);        
        int n;         

        System.out.print("Enter how many numbers to display");
        n = x.nextInt();
        int stop = n;

        if(n!=0) { //if statement checks if n!=0
            for ( int i = 0; i<=stop; i++) { 
                  //stop replaces n because n is incremented in your for-loop
                if(i%2==0) {
                    n += 2;
                    System.out.print(n);

                } else {
                    n += 3;
                    System.out.print(n);
                }  
            }
        }

    }
}

Upvotes: 1

npinti
npinti

Reputation: 52185

The problem is here: while(n!=0) and here: for ( int i = 0; i<=n; i++). For the while loop, will keep on going until n is equal to 0. For the for loop, this will most likely keep on going for ever.

Your code has two problems:

  1. If you provide a non negative value, this will keep on going for ever (since you are always only incrementing n).
  2. Even if you do supply a negative number, n would n need to become exactly 0 to stop.

Depending on what you need to do, you will need to change the condition. Judging by the output, n would need to be positive and thus you would need to stipulate some upper range for n in which the while loop would stop.

EDIT: You only need to have 1 loop to do what you are after. Also, n denotes the amount of elements, thus it needs to stay fixed throughout the execution of the program. In your case, you where increasing it all the time.

    Scanner x = new Scanner(System.in);
    int n;
    System.out.print("Enter how many numbers to display");
    n = x.nextInt();

    int count = 0;
    int i = 1;
    while (count < n) {                     //is this right?            
        if (count % 2 == 0) {
            System.out.print(i + " ");
            i += 2;
        } else {
            System.out.print(i + " ");
            i += 3;                
        }            
        count++;
    }

Upvotes: 3

Kishore Reddy
Kishore Reddy

Reputation: 926

Use 'if' condition in place of 'while' loop

Upvotes: 1

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