How to fill an array with int numbers using a loop in Java

Question

I am a newbie and I am to fulfill an exercise which is to write a simple program which would produce an array in console:

0,

0, 1,

0, 1, 2,

I failed at google searching similar problems which would direct me at a solution.

I will greatly appreciate your help. This is what i have been trying to build upon, but I am completely stuck:


    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int[] table = new int[11];
        for ( int i = 0; i <=10; i++){
            table[i] = i;
            System.out.println(i);
        }
    }

"produce an array in console" - note that the console is just a text output, i.e. there is no such thing as an array there. To produce output as wanted you could use 2 loops, one to iterate from 0 to your maximum value and inside that one that loops from 0 to the current value of the outer loop (e.g. for(int i = 0; i <= 10; i++ ) { for( int j = 0; j < i; j++) { /*print the number here*/ } /*print a linebreak here*/ }) — Thomas
– Thomas, Commented Oct 10, 2019 at 15:50

Vlad · Accepted Answer · 2019-10-10 15:57:33Z

1

You can try streams:

import java.util.stream.Collectors;
import java.util.stream.IntStream;

IntStream.range(0, 15).forEach(
        x -> System.out.println(
                IntStream.rangeClosed(0, x)
                         .mapToObj(String::valueOf)
                         .collect(Collectors.joining(", ")))
);

Output:

0
0, 1
0, 1, 2
0, 1, 2, 3
0, 1, 2, 3, 4
0, 1, 2, 3, 4, 5
0, 1, 2, 3, 4, 5, 6
0, 1, 2, 3, 4, 5, 6, 7
0, 1, 2, 3, 4, 5, 6, 7, 8
0, 1, 2, 3, 4, 5, 6, 7, 8, 9
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14

answered Oct 10, 2019 at 15:57

Vlad

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Comments

Avi · Accepted Answer · 2019-10-10 15:54:51Z

0

You should use Arrays.toString, like so:

import java.util.Arrays;

public class Main {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int[] table = new int[11];
        for ( int i = 0; i <=10; i++){
            table[i] = i;
            System.out.println(Arrays.toString(table));
        }
    }
}

However, this will print the entire array, as it is being populated:

[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 1, 2, 3, 0, 0, 0, 0, 0, 0, 0]
[0, 1, 2, 3, 4, 0, 0, 0, 0, 0, 0]
[0, 1, 2, 3, 4, 5, 0, 0, 0, 0, 0]
[0, 1, 2, 3, 4, 5, 6, 0, 0, 0, 0]
[0, 1, 2, 3, 4, 5, 6, 7, 0, 0, 0]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 0, 0]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

If you just want the elements filled so far, it's a little more involved:

import java.util.Arrays;

public class Main {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int[] table = new int[11];
        for ( int i = 0; i <=10; i++){
            table[i] = i;
            for(int j = 0; j <= i; j++)
            {
              System.out.print((j == 0 ? "" : ", ") + table[j]);
            }
            System.out.println();
        }
    }
}

Output:

0
0, 1
0, 1, 2
0, 1, 2, 3
0, 1, 2, 3, 4
0, 1, 2, 3, 4, 5
0, 1, 2, 3, 4, 5, 6
0, 1, 2, 3, 4, 5, 6, 7
0, 1, 2, 3, 4, 5, 6, 7, 8
0, 1, 2, 3, 4, 5, 6, 7, 8, 9
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10

answered Oct 10, 2019 at 15:54

Avi

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3 Comments

Mutton Over a year ago

The last one gives 100% expected results and it is still limited to "for" loop (this exercise is to use it) which makes for a perfect solution - thank you very much for your help!

Mutton Over a year ago

Now I am trying to document every line, so that I can uderstand it better and I am having a hard time figuring out what exactly happens here: ((j == 0 ? "" : ", ") + table[j])

Avi Over a year ago

@Mutton It says, "the current element, preceded by a comma and a space, IF this is not the first element on the line"

Dennis B. · Accepted Answer · 2019-10-10 15:52:03Z

0

You need two loops, one loop for the rows and then an additional loop for the numbers per row.

for (int i=0; i<=10; i++) {
  table[i] = i;
  for (int j=0; j<=i; j++) {
    System.out.print(table[j]);
  }
  System.out.print("\n");
}

Of course you might need to further format the output to your liking.

answered Oct 10, 2019 at 15:52

Dennis B.

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