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Filling 2D Array in Java and getting ExceptionOutOfBounds

I searched some entries, but could not answer my question correctly myself.
I'm trying to fill a 2-dimensional array with values.
As a test I'm currently doing this by trying to fill the array with the int number 1.
I do not understand my mistake.
public static void creatBoard () {
final int L = 6;
final int H = 6;
// Modell:
int [] [] board = new int [L] [H];
for (int i = 0; i<=board.length; i++) {
for (int j = 0; j<=board.length; j++) {
board [i] [j] = 1;
}
System.out.println("");
}

Use index 0 to length-1 (as array index start with 0)
public static void creatBoard () {
final int L = 6;
final int H = 6;
// Modell:
int [] [] board = new int [L] [H];
for (int i = 0; i<board.length; i++) {
for (int j = 0; j<board[i].length; j++) {
board [i] [j] = 1;
}
System.out.println("");
}
}

just debug it and you can see, that
for (int i = 0; i<=board.length; i++) {
for (int j = 0; j<=board.length; j++) {
board [i] [j] = 1;
}
System.out.println("");
}
i, and j change values from 0 to 6, it means that it get's out of arrays bounds ( you iterate over 7 lements, instead of 6 ), just remove = sign in loop bodies
for (int i = 0; i<board.length; i++) {
for (int j = 0; j<board[i].length; j++) {
board [i] [j] = 1;
}
System.out.println("");
}

Your board array is of size 6x6 hence the board.length is 6.
When you run the loop for (int j = 0; j<=board.length; ij+) it will run from 0 up to 6 but the array indexing is from 0 to 5. So when j=6, ExceptionOutOfBounds occurs since it will be referring to index board[0][6].
Change the condition in both the loops from <=board.length to <board.length

Two-dimentional arrays [duplicate]

This question already has answers here:
Syntax for creating a two-dimensional array in Java
(13 answers)
Closed 3 years ago.
I am working with 2-D arrays and I require help on this topic. My task is to create a 2-D array such that it is n by n (i.e. the number of rows and columns are equal). Fill the array with alternating 0's and 1's
void setup()
{
int n=3;
// code to populate the array
// code to display the output of array in a table format
/* output should be as follows:
The expected result when n=3 should be as the following:
1 0 1
0 1 0
1 0 1
*/
}

Solution:
class test{
public static void main(String[] args) {
int n = 3;
int[][] arr = setup(n);
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
System.out.print(arr[i][j]);
}
System.out.println();
}
}
static int[][] setup(int n){
int[][] arr = new int [n][n];
boolean even = false;
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
arr[i][j] = even ? 1 : 0;
even = !even;
}
}
return arr;
}
}
Output:
0 1 0
1 0 1
0 1 0

This should work.
You can replace the 3 that is given to n with any number you want as the 2D-Array's length.
void setup(){
int n = 3;
int count = 0;
int[][] myArray = new int[n][n];
for(int i = 0; i < n; i++){
for(int j = 0; j < n; j++){
if(count % 2 == 0){
myArray[i][j] = 1;
}
else{
myArray[i][j] = 0;
}
System.out.print(myArray[i][j] + " ");
count++;
}
System.out.println();
}
}
Output:
0 1 0
1 0 1
0 1 0

It's not complex, you just have to iterate two loops, that's it. Although you can get the solution on different ways.
public static void main(String[] args) {
int n = 3;
int [][] arr = new int[n][n];
int val = 1;
for(int i=0; i<n; i++) {
for(int j=0; j<n; j++) {
arr[i][j] = val;
val = (val == 0) ? 1 : 0;
}
}
for(int i=0; i<n; i++) {
for(int j=0; j<n; j++) {
System.out.print(arr[i][j] + " ");
}
System.out.println();
}
}
Output:
0 1 0
1 0 1
0 1 0

A simple implementation:
void setup()
{
int n=3;
final int[][] array = new int[n][n];
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
if ((n * i + j) % 2 == 0) {
array[i][j] = 1;
}
}
}
}

Here is how you can approach your logic , create a counter and negate each time after it prints value.
public static void main(String[] args) {
int counter = 0;
int n = 3;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
System.out.print(counter==0?1:0);
counter = ~counter;
}
System.out.println();
}
}
Output
101
010
101
Here is Online source code.

Merging two arrays and short that merged array

I got homework "Take two given array(already sorted up, for example {1,2,3}) and create a new array contains both arrays and then sort him up", we have a function to sort up arrays so it's not the problem, however it gets a little bit complex to me, here is my code:
public static Scanner in = new Scanner(System.in);
public static void main(String[] args) {
int[] a = new int[3];
int[] b = new int[5];
Help_arr.scan(a);
Help_arr.scan(b);
Help_arr.print(peula(a, b));
}
public static int[] peula(int[] a1, int[] b1) {
int[] c = new int[a1.length + b1.length];
for (int i = 0; i < a1.length; i++)
c[i] = a1[i];
for (int i = a1.length; i < c.length; i++){
c[i] = b1[i];
}
Help_arr.sortup(c);
return c;
}
Functions used from Help_arr class:
1) Scan an array:
public static void scan(int[] arr1) {
for (int i = 0; i < arr1.length; i++) {
System.out.println("Enter number" + (i + 1));
arr1[i] = in.nextInt();
}
}
2) Print an array:
public static void print(int[] arr1) {
for (int i = 0; i < arr1.length; i++) {
System.out.print(arr1[i] + " ");
}
}
3) Sort up an array:
public static void sortup(int[] arr1) {
int i, mini, temp, j;
for (j = 0; j < arr1.length; j++) {
mini = j;
for (i = j; i < arr1.length; i++) {
if (arr1[i] < arr1[mini])
mini = i;
}
temp = arr1[j];
arr1[j] = arr1[mini];
arr1[mini] = temp;
}
}
I get an error in the line c[i]=b1[i]; the array is going out of index bounds but I followed the code and this for will run until i=7 as the c.length is 8 and it is possible. But maybe I am missing something, here is the error:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 5
at arrays.PgRonTargilMivhan.peula(PgRonTargilMivhan.java:21)
at arrays.PgRonTargilMivhan.main(PgRonTargilMivhan.java:13)

The issue is with this code:
for (int i = a1.length; i < c.length; i++){
c[i] = b1[i];
here b1 index should start with 0 but you are starting with a1.length. You should have a separate index for b1 or use b1[i-a1.length].

Please find the logic ..
you were using 'i' index for array b is the problem.
Solution is below. Good luck
int[] c = new int[a.length + b.length];
int i = 0;
for (i = 0; i < a.length; i++)
c[i] = a[i];
for (int j = 0; j < b.length; j++)
c[i] = b[j];
}

How to flatten a 2-dimensional array into a 1-dimensional array

How would i transfer a 2d array into a 1d array in java. I have the code for the 2d array but dont know where to start.
The output of the 2d array is a 8 by 10 grid with the numbers going from 1-80.
public class move
{
public static void main (String[] args)
{
int[][] twoarray = new int[8][10];
int i ;
int j ;
for(i =0; i < 8; i++)
{
for(j = 0; j < 10; j++)
twoarray[i][j] = (i * 10 + j+1);
}
for(i = 0; i < 8; i++)
{
for(j = 0; j < 10; j++)
{
System.out.print(twoarray[i][j]);
System.out.print(" ");
}
System.out.println();
}
int[] array = new int[80];
}
}

Using Java 8
int[] array = Stream.of(twoarray)
.flatMapToInt(IntStream::of)
.toArray();
Using Java 7 or older
int[] array = new int[80];
int index = 0;
for (int[] row : twoarray) {
for (int val : row)
array[index++] = val;
}

You can do in your for loop:
int[] array = new int[80];
int k=0;
for(i = 0; i < 8; i++){
for(j = 0; j < 10; j++){
array[k++]=twoarray[i][j];
}
}

Convert 1D to 2D java.lang.ArrayIndexOutOfBoundsException

I try to convert 1D to 2D array, but I keep getting java.lang.ArrayIndexOutOfBoundsException, and I have tried whatever I could find on the stackoverflow or internet, but I do not understand why I have this issue?
public class Arrayto2DArray {
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
int[] a = {0,1, 6, 83, 4, 5, 12, 7};
int[][] b = new int[4][4];
for (int i = 0; i < b.length; i++) {
for (int j = 0; j < b[i].length; j++) {
b[i][j]=0;
System.out.print(b[i][j]);
}
System.out.println();
}
System.out.println("--------------------------");
for (int i = 0; i < 4; i++) {
for (int j = 0; j < b[i].length; j++) {
try{
b[i][j] = a[i+j*4];
}catch(Exception e){
e.printStackTrace();
System.out.println(e);
}
}
}
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
System.out.print(b[i][j]);
}
System.out.println();
}
}
}
I kind of know why I get this error and it because of this line
b[i][j] = a[i+j*4];
but I cannot come up any formula better than this.

Consider the second for-loop
Lets say when i = 3 and j= 3
a[i+j*4] evaluates to a[15] which is out of the array
When you declare you 2-d array, you specified int[][] b = new int[4][];, meaning that the first inner for loop for (int j = 0; j < b[i].length; j++) should result in a NullPointerException since b[i].length has no predefined length. Before intering the inner for loop, you should define the size of each b[i] like b[i] = new int[somenumber]
In regards to convert the 1d loop to a 2d, you need to define the rule around spliting it into the 2-d array. Then accordingly the second for loop need modification
EDIT:You modified your code to have an int[4][4] array, which means you have 16 placeholders. Your 1-d array contain only 8 placeholders. It depends on how you want to sort the array, like it can be
b 0 1 2 3
0 0 1 6 83
1 4 5 12 7
2 0 0 0 0
3 0 0 0 0
or any other pattern
Assuming the length of 1-d array is 8 and the total index of 2-d array is 16, the following is more of a general solution:
public static void main(String[] args) {
// TODO code application logic here
int[] a = { 0, 1, 6, 83, 4, 5, 12, 7 };
int[][] b = new int[4][4];
for (int i = 0; i < b.length; i++) {
for (int j = 0; j < b[i].length; j++) {
b[i][j] = 0;
System.out.print(b[i][j] + "\t");
}
System.out.println();
}
System.out.println("--------------------------");
for (int i = 0; i < 4; i++) {
for (int j = 0; j < b[i].length; j++) {
try {
if ((j + i * 4) < a.length)
b[i][j] = a[j + i * 4];
} catch (Exception e) {
e.printStackTrace();
System.out.println(e);
}
}
}
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
System.out.print(b[i][j] + "\t");
}
System.out.println();
}
}

What is wrong is your 2D array is a 4*4, so that means for each index, there will be 4 elements i.e. say values. So there would be a total of 16 values, so you would need a 1D array with 16 elements for the above code to work. Right now you have only 8 values in your 1D array.

I think your code should change like this
public class Arrayto2DArray {
public static void main(String[] args) {
// TODO code application logic here
int[] a = {0,1, 6, 83, 4, 5, 12, 7};
int[][] b = new int[4][2];
for (int i = 0; i < b.length; i++) {
for (int j = 0; j < b[i].length; j++) {
b[i][j]=0;
System.out.print(b[i][j]);
}
System.out.println();
}
System.out.println("--------------------------");
for (int i = 0; i < 4; i++) {
for (int j = 0; j < b[i].length; j++) {
try{
b[i][j] = a[i+j*4];
}catch(Exception e){
e.printStackTrace();
System.out.println(e);
}
}
}
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 2; j++) {
System.out.print(b[i][j]+" ");
}
System.out.println();
}
}
}

Your correct formula should be like.
int[] a = {0,1, 6, 83, 4, 5, 12, 7};
int[][] b = new int[4][2];
int k=0;
for (int i = 0; i < b.length; i++) { // Column of 2D array
for (int j = 0; j < b[0].length; j++) { // Row of 2D array
b[i][j]= a[k++];
System.out.println(b[i][j]);
}
}
Edit:
For general case, If your row is fixed at 4 but column is not fixed than your 2D conversion formula should be like below.
int col = a.length / 4;
int remainder = a.length % 4;
if (remainder > 0) {
col = col + 1; // Get the correct column size.
}
int[][] b = new int[4][col];
int k = 0;
for (int i = 0; i < 4; i++) {
for (int j = 0; j < col; j++) {
if (k < a.length) {
b[i][j] = a[k];
System.out.println(b[i][j]);
}
k++;
}
}