Code looks pretty good but the result is infinite repeated

Question about the task

One large array and two small ones

Java Syntax, Level 7, Lesson 4

Resolved

Don't know why it prints infnite second array.Code is beautiful

1. Create an array of 20 numbers.
2. Populate it with values from the keyboard.
3. Create two arrays of 10 numbers each.
4. Copy the large array into the two small ones: half the numbers into the first small array, and the second half into the second small array.
5. Display the second small array, each value on a new line.

Requirements:

The program must create an array of 20 integers.
The program should read 20 numbers from the keyboard for the large array.
The program must create two small arrays of 10 numbers each.
The program must copy one half of the large array into the first small array, copy the second half into the second array, and then display that array on the screen.

package com.codegym.task.task07.task0705; import java.io.BufferedReader; import java.io.InputStreamReader; /* One large array and two small ones */ public class Solution { public static void main(String[] args) throws Exception { //write your code here BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); int[] array = new int[20]; for(int i = 0 ; i <20 ; i ++){ array[i] = Integer.parseInt(reader.readLine()); } int[] largerarray = new int[10]; int[] smallerarray = new int[10]; for(int i = 0 ; i <10 ; i ++){ largerarray[i] = array[i]; } for(int j = 0 ; j <10 ; j++){ for(int i = 10 ; i < 20 ; i ++){ smallerarray[j] = array[i]; if(j < 10) System.out.println(smallerarray[j]); } } } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

26 October 2020, 17:03

Not infinite repeat. The output line is within the loop at line 26, so it is outputting something each time the inner loop cycles (10 times) then multiplied by the amount the outer loop runs (another 10 times). So instead of 10 outputs you are getting 100. Also, the smaller array is being filled only with the last input because the inner loop ends on the last input. This ends up outputting the last 10 values 10 times, and the smaller array being filled with 10 values that are the last input. It is probably hard to read because the indenting isn't proper:

for(int j = 0 ; j <10 ; j++){
   for(int i = 10 ; i < 20 ; i ++){
      smallerarray[j] = array[i];
      if(j < 10)
         System.out.println(smallerarray[j]);
   }
}

You can see the values in smaller array after your code runs by adding this line to line 32:

System.out.println(Arrays.toString(smallerarray));

Guanting Liu

Level 16 , Springfield, United States

27 October 2020, 05:14

So how should I fix it?It seems copy the first half is pretty simple,but when doing the second half the indexs can't match so it confuses me a lot

zimme

Level 14

27 October 2020, 05:59

create another for loop and try something like: smallsecondarray[i-10]=largearray[i]

Guadalupe Gagnon

Level 37 , Tampa, United States

27 October 2020, 13:23

solution

So making the small half is easy. You stick 10 numbers from the large array (indices 0-9) into the first smaller array. The problem that you correctly figured out is that using the loop counter for the second loop is not going to work because the indices 0-9 of the second smaller array have to be filled with the indices 10-19 of the larger array. I have two methods that I use that can be used to solve this: #1 create a counter for the large array that is used in both loops, so that when the second loop starts the large counter will be at 10; or #2 do something like zimme is suggesting. I would keep most of the your code the same, only removing the inner loop at line 26. Because the difference in index numbers from the large array to the second smaller array is going to be exactly 10 off, you can solve this by adding 10 to j when accessing the index of the larger array. So 2ndSmall[0] = large[0+10] 2ndSmall[1] = large[1+10] 2ndSmall[2] = large[2+10] etc.... Just make sure that you are outputting the values of the second small array only 1 time each