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How can I check if every single int in a randomly generated array is even and make it create another random array if it's not?

So I'm trying to create a program that creates a randomly generated array with numbers between 0 and 10.
Every time a number inside the 4x4 array is odd I want it to generate a brand new array and print every array discarded aswell until it creates a 4x4 array with only even numbers.
The problem right now is that I can't understand how to fix the last for and make it work properly with the boolean b that is supposed to restart the creation of the array.
import java.util.Scanner;
public class EvenArrayGenerator {
public static void main(String a[]) {
Boolean b;
do {
b = true;
int[][] Array = new int[4][4];
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++)
Array[i][j] = (int) (Math.random() * 11);
}
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
System.out.print(Array[i][j] + " ");
}
System.out.println();
}
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
if (Array[i][j] % 2 != 0)
b = false;
}
}
} while (b);
}
}

public class ArrayGen {
private int[][] array = new int[4][4];
private int iterations = 1; // you always start with one iteration
public static void main (String[] args) {
ArrayGen ag = new ArrayGen();
ag.reScramble();
while(!ag.isAllEven()) {
ag.reScramble();
ag.iterations++;
}
// this is just a nice visualisation
for (int i = 0; i < 4; i++) {
System.out.print("[");
for (int j = 0; j < 4; j++) {
System.out.print(ag.array[i][j] +((j != 3)? ", " : ""));
}
System.out.print("]\n");
}
System.out.println(ag.iterations + " iterations needed to get all-even array.");
}
private void reScramble () {
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
array[i][j] = (int)(Math.random() * 11);
}
}
}
private boolean isAllEven () {
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
if (array[i][j] % 2 == 1) {
return false;
}
}
}
return true;
}
}
I think this is a good solution. Refactoring your code into structured methods is never a bad idea. I hope this helps!

You are looping until you get an array that's all even. You should initialize b to be false, and update it to true in the (nested) for loop. Note that once's you've set it to false, there's no reason checking the other members of the array, and you can break out of the for loop.
Note, also, that using stream could make this check a tad more elegant:
b = Arrays.stream(arr).flatMapToInt(Arrays::stream).anyMatch(x -> x % 2 != 0)

What about generating random numbers up to 5 and double it? Then you don't have two check if they are even.

Instead of your last for loop:
for(int i=0;i<4;i++){
for(int j=0;j<4;j++){
if(Array[i][j] % 2!=0){
b=false;
break;
}
}
if(!b){
break;
}
}
if(!b){
break;
}
Alternatively, you could do an oddity check when you are generating the elements. Something like:
int element;
for(int i=0;i<4;i++){
for(int j=0;j<4;j++){
do{
element = (int)(Math.random()*11);
}while(element % 2 !=0)
Array[i][j] = element;
}
}
That way you don't have to check the values, they will always be even.

This should work:
import java.util.Scanner;
public class EvenArrayGenerator{
public static void main(String a[]){
boolean anyOdd;
int array = 0;
do{
System.out.println ("Array " + ++array + ":");
anyOdd=false;
int[][] Array = new int[4][4];
for(int i=0;i<4;i++) {
for(int j=0;j<4;j++) {
Array[i][j] = (int)(Math.random()*11);
}
}
for(int i=0;i<4;i++){
for(int j=0;j<4;j++){
System.out.print(Array[i][j] + " ");
}
System.out.println();
}
for(int i=0;i<4;i++){
for(int j=0;j<4;j++){
anyOdd |= Array[i][j] % 2!=0;
}
}
} while(anyOdd);
}
}
As you can see, I just modified the condition from b to anyOdd, so if there is any odd number, it will iterate again.
Also, you can check it when you generate the random numbers, so you avoid a second loop:
import java.util.Scanner;
public class EvenArrayGenerator{
public static void main(String a[]){
boolean anyOdd;
int array = 0;
do{
System.out.println ("Array " + ++array + ":");
anyOdd=false;
int[][] Array = new int[4][4];
for(int i=0;i<4;i++) {
for(int j=0;j<4;j++) {
Array[i][j] = (int)(Math.random()*11);
anyOdd |= array[i][j] % 2 != 0;
}
}
for(int i=0;i<4;i++){
for(int j=0;j<4;j++){
System.out.print(Array[i][j] + " ");
}
System.out.println();
}
} while(anyOdd);
}
}

public class EvenArrayGenerator {
public static void main(String a[]) {
int[][] arr = createAllEvenArray(4);
printArray(arr);
}
private static int[][] createAllEvenArray(int size) {
while (true) {
int[][] arr = createArray(size);
printArray(arr);
if (isAllEven(arr))
return arr;
}
}
private static int[][] createArray(int size) {
int[][] arr = new int[size][size];
for (int i = 0; i < arr.length; i++)
for (int j = 0; j < arr.length; j++)
arr[i][j] = (int)(Math.random() * 11);
return arr;
}
private static void printArray(int[][] arr) {
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
if (j > 0)
System.out.print("\t");
System.out.format("%2d", arr[i][j]);
}
System.out.println();
}
System.out.println();
}
private static boolean isAllEven(int[][] arr) {
for (int i = 0; i < arr.length; i++)
for (int j = 0; j < arr.length; j++)
if (arr[i][j] % 2 != 0)
return false;
return true;
}
}

Check whether this matrix is symmetric in relation to the main diagonal

Given the number n, not exceeding 10, and a matrix of size n × n.
Check whether this matrix is symmetric in relation to the main diagonal. Output the word “YES”, if it is symmetric and the word “NO” otherwise.
This is my code, it unfortunately does not work. Please, explain to me how to do it correctly :)
public class Main { public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n= scanner.nextInt();
int[][] number = new int[n][n];
boolean ismatch = false;
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
number[i][j] = scanner.nextInt();
}
}
int unevenchecker = (n% 2);
if (unevenchecker != 0) {
for (int k = 0; k < number.length - 1; k++) {
for (int l = 0; l < number.length - 1; l++) {
if (number[k][l] == number[l][k]) {
ismatch = true;
}
}
}
if (ismatch) {
System.out.print("YES");
}
} else {
System.out.print("NO");
}
}
}

The matrix is not symmetric if you find at least 1 symmetric couple where the 2 parts are not equal, so instead of checking for equality inside the loop, check for inequality:
ismatch = true;
for (int k = 0; k < number.length - 1; k++) {
for (int l = 0; l < number.length - 1; l++) {
if (number[k][l] != number[l][k]) {
ismatch = false;
break;
}
}
}

public class Main {
static boolean isSymmetric(int mat[][], int size) {
for (int i = 0; i < size; i++)
for (int j = i + 1; j < size - i; j++)
if (mat[i][j] != mat[j][i])
return false;
return true;
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n= scanner.nextInt();
int[][] number = new int[n][n];
boolean ismatch = false;
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
number[i][j] = scanner.nextInt();
}
}
if (isSymmetric(number, n)) {
System.out.print("YES");
} else {
System.out.print("NO");
}
}
}
Notice that the nested loop into isSymmetric starts from j = i + 1, for not checking twice same condition.

Java out patterns

I'm currently trying to get this output using nested loops:
For the life of me I cannot figure out how to get the # signs to increment by +2 each time. Any help would be greatly appreciated!
public class PrintPatterns {
public static void main(String[] args) {
pattern1();
}
private static void pattern1() {
for (int i = 1; i <= 10; i++) {
for (int j = 0; j < 10; j += 2); {
System.out.print("# ");
}
for (int j = 0; j < 2; j++) {
System.out.print(". ");
}
for (int j = 1; j < 10 - i; j++) {
System.out.print("x ");
}
System.out.println();
}
}
}

This code does what you want:
private static void pattern1() {
StringBuilder stringBuilder = new StringBuilder();
for (int ats = 2; ats <= 10; ats += 2) {
for (int j = 0; j < ats; j++) {
stringBuilder.append("# ");
}
stringBuilder.append(". . ");
for (int j = 0; j <= 10 - ats; j++) {
stringBuilder.append("x ");
}
stringBuilder.append("\n");
}
System.out.println(stringBuilder.toString());
}
One mistake you did in your code is that you put a ; after your for loop, this will end the loop right there.
Also do not use System.out.println() in loops. As using IO will slow down your application. Use StringBuilder to build strings and then output all at once.

Instead of:
for (int j = 0; j < 10; j += 2); {
System.out.print("# ");
}
Try:
for (int j = 0; j < 2 * i; j += 1) {
System.out.print("# ");
}

public class PrintPatterns
{
public static void main(String[] args)
{
pattern1();
}
private static void pattern1()
{
for(int i = 1; i <= 10; i++)
{
for(int j = 1; j < i+2; j++)
{
System.out.print("# ");
}
for(int j = 0; j < 2; j++)
{
System.out.print(". ");
}
for(int k = 10-i; k > 0; k--)
{
System.out.print("x ");
}
System.out.println();
}
}
}

Translate while loop to do while

Very simple but I cannot seem to figure it out, I simply need to translate the while loops into do-while. Objective is to print 1-9 and 9-1 one as such "1,22,333,4444" etc. Thank you if you help me!
int y = 1;
int x = 1;
while (x < 10) {
y = 1;
while (y <= x) {
y++;
System.out.print(x + "");
}
System.out.println();
x++;
}
int a = 9;
int b = 1;
while (a >=1) {
b = 1;
while (b<= a) {
b++;
System.out.print(a + "");
}
System.out.println();
a--;
}
My attempt prints 1-9 but as single numbers and infinitely runs, but does not print anything after 9 the first time.
int c = 1;
int d =1;
do { System.out.print(c +"");
c++;
System.out.println();
}
while (c<10);{
y=1;
while (d<=c);
}

Looks like we are doing your homework...
public class Test {
public static void main(String[] args) {
int c = 1;
do {
int d =1;
do{
System.out.print(c);
d++;
} while (c>=d);
System.out.println("");
c++;
}
while (c<10);
}
}

This is a basic usage:
x=1;
do{
//hello
x++;
} while(x<=10);
Apply it as you need. We can't really do your homework.

What you want is a nested do-while.
int x = 1;
do {
int p = 0;
do {
System.out.print(x);
}
while(p < x)
System.out.println();
x++;
}
while(x < 10)
But I should probably add a for loop would make a lot more sense here:
for(int x = 0; x < 10; x++)
{
for(int p = 0; p < x; p++)
{
System.out.print(x);
}
System.out.println();
}

As you want to run in infinite loop just use:
do {
int c = 1;
do {
System.out.println(c);
c++;
} while (c < 10);
} while (true);

This will run infinitely and print your desired strings:
StringBuilder result1= new StringBuilder();
StringBuilder result2 = new StringBuilder();
do
{
for(int i = 1; i < 10; i++)
{
for(int j = 0; j < i; j++)
{
result1.append(i);
}
result1.append(",");
}
for(int i = 9; i > 0; i--)
{
for(int j = 0; j < i; j++)
{
result2.append(i);
}
result2.append(",");
}
System.out.println(result1);
System.out.println(result2);
}while(true);

How to print a two dimensional array?

I have a [20][20] two dimensional array that I've manipulated. In a few words I am doing a turtle project with user inputting instructions like pen up = 0 and pen down = 1. When the pen is down the individual array location, for instance [3][4] is marked with a "1".
The last step of my program is to print out the 20/20 array. I can't figure out how to print it and I need to replace the "1" with an "X". The print command is actually a method inside a class that a parent program will call. I know I have to use a loop.
public void printGrid() {
System.out.println...
}

you can use the Utility mettod. Arrays.deeptoString();
public static void main(String[] args) {
int twoD[][] = new int[4][];
twoD[0] = new int[1];
twoD[1] = new int[2];
twoD[2] = new int[3];
twoD[3] = new int[4];
System.out.println(Arrays.deepToString(twoD));
}

public void printGrid()
{
for(int i = 0; i < 20; i++)
{
for(int j = 0; j < 20; j++)
{
System.out.printf("%5d ", a[i][j]);
}
System.out.println();
}
}
And to replace
public void replaceGrid()
{
for (int i = 0; i < 20; i++)
{
for (int j = 0; j < 20; j++)
{
if (a[i][j] == 1)
a[i][j] = x;
}
}
}
And you can do this all in one go:
public void printAndReplaceGrid()
{
for(int i = 0; i < 20; i++)
{
for(int j = 0; j < 20; j++)
{
if (a[i][j] == 1)
a[i][j] = x;
System.out.printf("%5d ", a[i][j]);
}
System.out.println();
}
}

Something like this that i answer in another question
public class Snippet {
public static void main(String[] args) {
int [][]lst = new int[10][10];
for (int[] arr : lst) {
System.out.println(Arrays.toString(arr));
}
}
}

public static void printTwoDimensionalArray(int[][] a) {
for (int i = 0; i < a.length; i++) {
for (int j = 0; j < a[i].length; j++) {
System.out.printf("%d ", a[i][j]);
}
System.out.println();
}
}
just for int array

Well, since 'X' is a char and not an int, you cannot actually replace it in the matrix itself, however, the following code should print an 'x' char whenever it comes across a 1.
public void printGrid(int[][] in){
for(int i = 0; i < 20; i++){
for(int j = 0; j < 20; j++){
if(in[i][j] == 1)
System.out.print('X' + "\t");
else
System.out.print(in[i][j] + "\t");
}
System.out.print("\n");
}
}

You should loop by rows and then columns with a structure like
for ...row index...
for ...column index...
print
but I guess this is homework so just try it out yourself.
Swap the row/column index in the for loops depending on if you need to go across first and then down, vs. down first and then across.

How about trying this?
public static void main (String [] args)
{
int [] [] listTwo = new int [5][5];
// 2 Dimensional array
int x = 0;
int y = 0;
while (x < 5) {
listTwo[x][y] = (int)(Math.random()*10);
while (y <5){
listTwo [x] [y] = (int)(Math.random()*10);
System.out.print(listTwo[x][y]+" | ");
y++;
}
System.out.println("");
y=0;
x++;
}
}

If you know the maxValue (can be easily done if another iteration of the elements is not an issue) of the matrix, I find the following code more effective and generic.
int numDigits = (int) Math.log10(maxValue) + 1;
if (numDigits <= 1) {
numDigits = 2;
}
StringBuffer buf = new StringBuffer();
for (int i = 0; i < matrix.length; i++) {
int[] row = matrix[i];
for (int j = 0; j < row.length; j++) {
int block = row[j];
buf.append(String.format("%" + numDigits + "d", block));
if (j >= row.length - 1) {
buf.append("\n");
}
}
}
return buf.toString();

I am also a beginner and I've just managed to crack this using two nested for loops.
I looked at the answers here and tbh they're a bit advanced for me so I thought I'd share mine to help all the other newbies out there.
P.S. It's for a Whack-A-Mole game hence why the array is called 'moleGrid'.
public static void printGrid() {
for (int i = 0; i < moleGrid.length; i++) {
for (int j = 0; j < moleGrid[0].length; j++) {
if (j == 0 || j % (moleGrid.length - 1) != 0) {
System.out.print(moleGrid[i][j]);
}
else {
System.out.println(moleGrid[i][j]);
}
}
}
}
Hope it helps!

more simpler approach , use java 5 style for loop
Integer[][] twoDimArray = {{8, 9},{8, 10}};
for (Integer[] array: twoDimArray){
System.out.print(array[0] + " ,");
System.out.println(array[1]);
}