GUI.java ändert die Textfields nicht

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.*;
import java.awt.event.*;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JSplitPane;
import javax.swing.JScrollPane;
import javax.swing.JTextField;

import java.awt.Color;


public class GUI extends JFrame {

	private JPanel contentPane;
	private JTextField[][] allField = new JTextField[9][9];	//IMPORTANT!!!: first [] here is the column and second [] the row!!!

	/**
	 * Launch the application.
	 */
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					GUI frame = new GUI();
					frame.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
	}

	/**
	 * Create the frame.
	 */
	public GUI() {
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setBounds(100, 100, 310, 362);
		contentPane = new JPanel();
		contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
		setContentPane(contentPane);
		contentPane.setLayout(null);
		contentPane.setBackground(Color.DARK_GRAY);
		
		JButton btnNewButton = new JButton("Solve");
		btnNewButton.setBounds(10, 285, 89, 23);
		btnNewButton.setBackground(Color.white);
		contentPane.add(btnNewButton);
		btnNewButton.addActionListener(new ActionListener()
		{
		  public void actionPerformed(ActionEvent e)
		  {
			  readSudoku();
		  }
		});
		
		for(int i=0; i<9; i++){
			for(int j=0; j<9; j++){
				allField[i][j] = new JTextField();
			    allField[i][j].setBounds(10 + i * 30, 10 + j * 30, 30, 30);
			    allField[i][j].setColumns(1);
			    allField[i][j].setBorder(BorderFactory.createLineBorder(Color.DARK_GRAY, 1));
			    contentPane.add(allField[i][j]);
			}
		}
		for(int i=3; i<6; i++){
			for(int j=0; j<3; j++){
				allField[i][j].setBackground(Color.LIGHT_GRAY);
			}
		}
		for(int i=3; i<6; i++){
			for(int j=6; j<9; j++){
				allField[i][j].setBackground(Color.LIGHT_GRAY);
			}
		}
		for(int i=0; i<3; i++){
			for(int j=3; j<6; j++){
				allField[i][j].setBackground(Color.LIGHT_GRAY);
			}
		}
		for(int i=6; i<9; i++){
			for(int j=3; j<6; j++){
				allField[i][j].setBackground(Color.LIGHT_GRAY);
			}
		}
	}
	
	public void readSudoku(){
		int [][]array = new int[9][9];	//first [] is the row second [] the column. Order differs from declaration of allField[][] but is important  to know for Main.java.
		for( int i=0; i<9; i++){
			for( int j=0; j<9; j++){
				if(!allField[i][j].getText().isEmpty()) array[i][j] = Integer.parseInt(allField[i][j].getText());
				else array[i][j] = 0;
			}
		}
		Main start = new Main();
		start.startSolving(array);
	}
	
	public void writeSudoku(int[][] array){
		for(int i=0; i<9; i++){
			for(int j=0; j<9; j++){
				System.out.println(String.valueOf(array[i][j]));
				allField[i][j].setText(String.valueOf(array[i][j]));
			}
		}
	}
}

public class Main{

	public void startSolving(int[][] array){
		int workArray[][] = array;	//contains the Sudoku
		int counter = 1;	//counts how many nums have been solved in one round. 1 to get into while.
		long startingTime = System.nanoTime();	//Time that solving start. Need for time measurement.
		while(counter>0){
			counter = 0;	//set to 0. now the counting begins.
			for(int n=1; n<10; n++){	//for every number
				int tempArray[][] = new int[9][9];	//contains the possibilities of the choosen number. If it can be at [x][y]
				for(int r=0; r<9; r++){	//for every row
					for(int c=0; c<9; c++){	//for every column
						if(workArray[r][c] == 0){	//if number already exists at this field nothing is left to show (*)
							if(!checkRow(r, n, c, workArray) && !checkColumn(c, n, r, workArray) && !checkBox(r, c, n, workArray)) tempArray[r][c] = 1;	//if num is nowhere set 1(possible)
							else tempArray[r][c] = 0;	//is num is anywhere set 0(not p)
						}
						else tempArray[r][c] = 0;	//(*)even though tempArray still needs to be written
					}
				}
				//now it need to be checked if there is just one p in every row/column/box
				//doing that by looking for a field with p of num being there and looking if there are other p in this special row/column/box
				for(int r=0; r<9; r++){	//for every row
					for(int c=0; c<9; c++){	//for every column
						if(tempArray[r][c] == 1){	//if it is possible for the number to be there -> check if it is must be there
							if(checkRowPossibilities(r, c, tempArray)){ workArray[r][c] = n; counter++;}//check the row
							else if(checkColumnPossibilities(c, r, tempArray)){ workArray[r][c] =n; counter++;}	//check the column
							else if(checkBoxPossibilities(r, c, tempArray)){ workArray[r][c] = n; counter++;}	//check the box
						}
					}
				}
			}
			
		}
		long estimatedTime = System.nanoTime() - startingTime;	//Time that was needed.
		GUI endSudoku = new GUI();
		endSudoku.writeSudoku(workArray);
		System.out.println(estimatedTime);
	}
	
	
	
	
	
//	takes integer row that represents the row.
//	takes integer num that represents the searched number.
//	takes integer field that represents the column/field that is tested in main method.
//	takes array that represents the Sudoku.
//	returns if number is already in this row.
	
	public static boolean checkRow(int row, int num, int field, int[][] array){
		for( int c=0; c<9; c++){
			if(c != field) if(array[row][c] == num) return true;
		}
		return false;
	}
	
	
	
	
	
//	takes integer column that represents the column.
//	takes integer num that represents the searched number.
//	takes integer field that represents the row/field that is tested in main method.
//	takes array that represents the Sudoku.
//	returns if number is in this column.
	
	public static boolean checkColumn(int column, int num, int field, int[][] array){
		for( int r=0; r<9; r++){
			if(r != field) if(array[r][column] == num) return true;
		}
		return false;
	}
	
	
	
	
	
//	takes integer row that represents the row.
//	takes integer column that represents the column.
//	takes integer num that represents the searched number.
//	takes array that represents the Sudoku.
//	returns if number is in this box.
	
	public static boolean checkBox(int row, int column, int num, int[][] array){
			if(row == 0 || row == 1 || row == 2){	//row is one of the first 3
				return checkBoxColumn( column, row, num, 0, array);
			}
			else if(row == 3 || row == 4 || row == 5){	//row is one of the middle 3
				return checkBoxColumn( column, row, num, 3, array);
			}
			else{	//row is one of the last 3
				return checkBoxColumn( column, row, num, 6, array);
			}
	}
	
//	extention of checkBox.
//	takes integer column that represents the column.
//	takes integer row that represents the row.
//	takes integer num that represents the searched number.
//	takes array that represents the Sudoku.
//	takes integer startRow that represents the starting number for the for-loop. Comes from the row-check.
//	returns if number is in the box.(to checkBox)
	
	public static boolean checkBoxColumn(int column, int row, int num, int startRow, int[][] array){
		if(column == 0 || column == 1 || column == 2){	//column is one of the first 3
			for(int r=startRow; r<startRow+3; r++){
				for(int c=0; c<3; c++){
					if(r != row || c != column) if(array[r][c] == num) return true;
				}
			}
		}
		else if(column == 3 || column == 4 || column == 5){	//column is one of the middle 3
			for(int r=startRow; r<startRow+3; r++){
				for(int c=3; c<6; c++){
					if(r != row || c != column) if(array[r][c] == num) return true;
				}
			}
		}
		else{	//column is one of the last 3
			for(int r=startRow; r<startRow+3; r++){
				for(int c=6; c<9; c++){
					if(r != row || c != column) if(array[r][c] == num) return true;
				}
			}
		}
		return false;
	}
	
	
	
	
	
//	takes integer row that represents the row.
//	takes integer field that represents the column/field that is tested in main method.
//	takes array that represents the posibilities of num being at [x][y].
//	returns if it is the only possibility in this row.
	
	public static boolean checkRowPossibilities(int row, int field, int[][] array){
		for( int c=0; c<9; c++){
			if(c != field) if(array[row][c] == 1) return false;	//returns false if the checked field is not alone in this row
		}
		return true;	//returns true -> yes IS alone!
	}
	
	
	
	
	
//	takes integer column that represents the column.
//	takes integer field that represents the row/field that is tested in main method.
//	takes array that represents the possibilities of num being at [x][y].
//	returns if it is the only possobility in this column.
	
	public static boolean checkColumnPossibilities(int column, int field, int[][] array){
		for( int r=0; r<9; r++){
			if(r != field) if(array[r][column] == 1) return false;	//returns false if the checked field is not alone in this row
		}
		return true;	//returns true -> yes IS alone!
	}
	
	
	
	
//	takes integer row that represents the row.
//	takes integer column that represents the column.
//	takes array that represents the possibilities of num being at [x][y].
//	returns if it is the only possobility in this column.
	
	public static boolean checkBoxPossibilities(int row, int column, int[][] array){
			if(row == 0 || row == 1 || row == 2){	//row is one of the first 3
				return checkBoxPossibilitiesColumn( column, row, 0, array);
			}
			else if(row == 3 || row == 4 || row == 5){	//row is one of the middle 3
				return checkBoxPossibilitiesColumn( column, row, 3, array);
			}
			else{	//row is one of the last 3
				return checkBoxPossibilitiesColumn( column, row, 6, array);
			}
	}
	
//	extention of checkBoxPossibilities.
//	takes integer column that represents the column.
//	takes integer row that represents the row.
//	takes array that represents the possibilities of num being at [x][y].
//	takes integer startRow that represents the starting number for the for-loop. Comes from the row-check.
//	returns if it is the only possobility in this column.(to checkBox)
	
	public static boolean checkBoxPossibilitiesColumn(int column, int row, int startRow, int[][] array){
		if(column == 0 || column == 1 || column == 2){	//column is one of the first 3
			for(int r=startRow; r<startRow+3; r++){
				for(int c=0; c<3; c++){
					if(r != row || c != column) if(array[r][c] == 1) return false;	//returns false if the checked field is not alone in this row
				}
			}
		}
		else if(column == 3 || column == 4 || column == 5){	//column is one of the middle 3
			for(int r=startRow; r<startRow+3; r++){
				for(int c=3; c<6; c++){
					if(r != row || c != column) if(array[r][c] == 1) return false;	//returns false if the checked field is not alone in this row
				}
			}
		}
		else{	//column is one of the last 3
			for(int r=startRow; r<startRow+3; r++){
				for(int c=6; c<9; c++){
					if(r != row || c != column) if(array[r][c] == 1) return false;	//returns false if the checked field is not alone in this row
				}
			}
		}
		return true;	//returns true -> yes IS alone!
	}
}