CODEWITHSUNDEEP
javaloopsfor-loopiteration
Krish Vachhani
Krish Vachhani

Reputation: 11

I am trying to make a pattern (triangle in java)

I am trying to make this pattern in java:

* * * * * * * * 
* * * * * * * 
* * * * * * 
* * * * * 
* * * * 
* * * 
* * 
*

This is the code which I have written:

package practise;
import java.util.Scanner;
public class PatternsUsingLoop {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();       
        for(int j=1;j<=n;j++) { 
            for(int k=n;k>=1;k--) {

                System.out.print("* ");
            }
            System.out.println();
        }
    }
}

please tell me the error

Upvotes: 0

Views: 95

Answers (4)

Arvind Kumar Avinash
Arvind Kumar Avinash

Reputation: 79425

There are many ways to do it also to fix this issue. One of the simplest fixes is to replace the inner loop with the following:

for (int k = (n - j) + 1; k >= 1; k--)

Since you want to print n number of *s in the first line, n - 1 number of *s in the second line and so on, the value of k must be initialized to n when j is 1, n - 1 when j is 2 and so on.

Some of the other ways to do this requirement are as follows:

A.

for (int j = n; j >= 1; j--) {
    for (int k = j; k >= 1; k--) {
        System.out.print("* ");
    }
    System.out.println();
}

B.

for (int j = n; j >= 1; j--) {
    for (int k = 1; k <= j; k++) {
        System.out.print("* ");
    }
    System.out.println();
}

...and many more

Upvotes: 2

Vaibhav Srivastava
Vaibhav Srivastava

Reputation: 1

Its a very small mistake that you are doing , the first loop is correct but in the inner loop you are printing n stars again (from n to 1). You need to print (n - i + 1) stars for every loop.

Use this change : 

...
...
int n = sc.nextInt();       
        for(int j=1;j<=n;j++) { 
            for(int k=n-j+1;k>=1;k--) {

                System.out.print("* ");
            }
            System.out.println();
        }
...
...

//... means same code //

Upvotes: 0

pmc
pmc

Reputation: 1015

The problem is that you haven't tried debugging your code. To debug your code try printing out the variables that you are using at the beginning of each line to see if they are what you expect. You have (hopefully) thought about the code, and what you think each variable will be on each line, so you've missed something, you have a bug.

For example try this:

package practise;
import java.util.Scanner;
public class PatternsUsingLoop {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();       
        for(int j=1;j<=n;j++) { 
            System.out.print("j: " + j + " n: " + n);
            for(int k=n;k>=1;k--) {
                System.out.print("* ");
            }
            System.out.println();
        }
    }
}

When you run that you get

j: 1 n: 5* * * * * 
j: 2 n: 5* * * * * 
j: 3 n: 5* * * * * 
j: 4 n: 5* * * * * 
j: 5 n: 5* * * * *

Which shows what a couple of the other answers are pointing out, that n doesn't change so the output is always 5 stars.

Now you can figure out the answer. (Hint: start j from 0 and use k=n-j)

Upvotes: 0

Kerim
Kerim

Reputation: 125

You don't decrease the finish condition in inner loop. This will works:

    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    for(int row=0;row<n;row++) { 
        for (int column = 0; column < n-row; column++) {
            System.out.print("* ");
        }
        System.out.println();
    }

Upvotes: 1

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