Last condition doesnt verify

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HELP please

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; import java.util.Scanner; /* One large array and two small ones */ public class Solution { public static void main(String[] args) throws Exception { Scanner sc = new Scanner(System.in); int arrL[] = new int[20]; int arr1[] = new int[10]; int arr2[] = new int[10]; for(int i = 0; i < arrL.length; i++){ arrL[i] = sc.nextInt(); } for(int i = 0; i < arrL.length/2; i++){ arr1[i] = arrL[i]; System.out.println(arr1[i]); } for(int i = arrL.length/2; i < arrL.length; i++){ arr2[i] = arrL[i]; System.out.println(arr2[i]); } } }

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Artem Divertitto Senior Android Developer at United Tech

17 December 2019, 14:59

And you must print only second array

Shuy

Level 9 , Frankfurt, Germany

17 December 2019, 14:52

Line 24: youre trying to access Index 10 of the Array arr2, while it only has 0-9 Index.

Guadalupe Gagnon

Level 37 , Tampa, United States

17 December 2019, 14:51

at line 24 you are starting i to be 10, then trying to access index 10 of arr2 (the max in arr2 is only 9). You will need to fix this.

Lelush

Level 7

17 December 2019, 15:08

public class Solution { public static void main(String[] args) throws Exception { Scanner sc = new Scanner(System.in); int arrL[] = new int[20]; int arr1[] = new int[10]; int arr2[] = new int[10]; for(int i = 0; i < arrL.length; i++){ arrL[i] = sc.nextInt(); } for(int i = 0; i < arrL.length/2; i++){ arr1[i] = arrL[i]; } for(int i = 0; i < 10; i++){ for(int j = 10; j < 20; j++){ arr2[i] = arrL[j]; } System.out.println(arr2[i]); } } } What is wrong with it?

Guadalupe Gagnon

Level 37 , Tampa, United States

17 December 2019, 15:16

useful

for(int i = 0; i < 10; i++){ // outer loop
   for(int j = 10; j < 20; j++){ // inner loop
      arr2[i] = arrL[j];
   }

   System.out.println(arr2[i]);
}

for each time that the outer loop iterates, the inner loop will iterate 10 times. So when i = 0, the inner loop will do this: j = 10 -- arr2[0] = arrL[10]; j = 11 -- arr2[0] = arrL[11]; j = 12 -- arr2[0] = arrL[12]; j = 13 -- arr2[0] = arrL[13]; j = 14 -- arr2[0] = arrL[14]; etc... The next cycle of i, when i = 1: j = 10 -- arr2[1] = arrL[10]; j = 11 -- arr2[1] = arrL[11]; j = 12 -- arr2[1] = arrL[12]; j = 13 -- arr2[1] = arrL[13]; j = 14 -- arr2[1] = arrL[14]; etc... i = 2: j = 10 -- arr2[2] = arrL[10]; j = 11 -- arr2[2] = arrL[11]; j = 12 -- arr2[2] = arrL[12]; j = 13 -- arr2[2] = arrL[13]; j = 14 -- arr2[2] = arrL[14]; etc... This will eventually lead to every index of arr2 equal to arrL[19]

Lelush

Level 7

17 December 2019, 18:39

thanks, i changed my code, but i don't know how exactly it works. can you please explain it? Thank tou in advance public static void main(String[] args){ Scanner sc = new Scanner(System.in); int arrL[] = new int[20]; int arr1[] = new int[10]; int arr2[] = new int[10]; for(int i = 0; i < arrL.length; i++){ arrL[i] = sc.nextInt(); } for (int i = 0; i < arrL.length; i++) { if (i < arr1.length) arr1[i] = arrL[i]; else arr2[i - arr1.length] = arrL[i]; } for(int i = 0; i < arr2.length; i++) System.out.println(arr2[i]); } }

Guadalupe Gagnon

Level 37 , Tampa, United States

17 December 2019, 19:00

solution

for (int i = 0; i < arrL.length; i++){
   if (i < arr1.length)
      arr1[i] = arrL[i];
   else
      arr2[i - arr1.length] = arrL[i];
}

this bit of code correctly implements the task conditions. When i is less than arr1.length (meaning i is between 0 and 9) it will fill in the first 10 numbers from arrL. Then, when i is 10 and greater, it will put the rest of values from arrL into arr2. arr1.length is equal to 10. So when i is 10, the line arr2[i - arr1.length] = arrL[i]; will be: arr2[10 - 10] = arrL[10]; // arr2[0] = arrL[10] next iteration, i = 11: arr2[11 - 10] = arrL[11]; // arr2[1] = arrL[11] arr2[12 - 10] = arrL[12]; // arr2[2] = arrL[12]

Lelush

Level 7

17 December 2019, 19:22

thank you so much, now everything is clear