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

问题

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, 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);
        }
    }

回答1:

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

回答2:

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

回答3:

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.

来源：https://stackoverflow.com/questions/58326653/how-to-fill-an-array-with-int-numbers-using-a-loop-in-java

标签

java

arrays

loops

for-loop