Java Android Studio For-loop exceeding its limit

Question

When i run the code below on my Android device, I get an ArrayOutOfBounds exception saying y = 6. However, this is theoretically not possible because the bounds of the for-loop is y < 6. I've searched for possible explanations and found none. The size of matrix1Numbers is 6 by 6, holding 0-5 for each dimension.

for (z = 0; z < 6; ++z) {
        for (y = 0; y < 6; ++y) {
            matrix1Numbers[z][y].addTextChangedListener(new TextWatcher() {
                @Override
                public void beforeTextChanged(  CharSequence s, int start, int count, int after) {

                }

                @Override
                public void onTextChanged(CharSequence s, int start, int before, int count) {
                    if (matrix1Numbers[z][y].getText().toString().equals("")) {
                        for (int a = 0; a < z; ++a) {
                            for (int b = y; b < 6; ++b) {
                                matrix1Numbers[a][b].setText("");
                                matrix1Numbers[a][b].setBackgroundColor(Color.WHITE);
                            }
                        }

                        for (int a = z; a < 6; ++a) {
                            for (int b = 0; b < y; ++b) {
                                matrix1Numbers[a][b].setText("");
                                matrix1Numbers[a][b].setBackgroundColor(Color.WHITE);
                            }
                        }

                        for (int a = z; a < 6; ++a) {
                            for (int b = y; b < 6; ++b) {
                                matrix1Numbers[a][b].setText("");
                                matrix1Numbers[a][b].setBackgroundColor(Color.WHITE);
                            }
                        }
                    } else {
                        if (z > matrix1MaxX) {
                            matrix1MaxX = z;
                        }
                        if (y > matrix1MaxY) {
                            matrix1MaxY = y;
                        }

                        for (int a = 0; a < matrix1MaxX; ++a) {
                            for (int b = 0; b < matrix1MaxY; ++b) {
                                matrix1Numbers[a][b].setBackgroundColor(Color.BLUE);
                            }
                        }
                    }
                }

                @Override
                public void afterTextChanged(Editable s) {

                }
            });


            matrix2Numbers[z][y].addTextChangedListener(new TextWatcher() {
                @Override
                public void beforeTextChanged(CharSequence s, int start, int count, int after) {

                }

                @Override
                public void onTextChanged(CharSequence s, int start, int before, int count) {
                    if (matrix2Numbers[z][y].getText().toString().equals("")) {
                        for (int a = 0; a < z; ++a) {
                            for (int b = y; b < 6; ++b) {
                                matrix2Numbers[a][b].setText("");
                                matrix2Numbers[a][b].setBackgroundColor(Color.WHITE);
                            }
                        }

                        for (int a = z; a < 6; ++a) {
                            for (int b = 0; b < y; ++b) {
                                matrix2Numbers[a][b].setText("");
                                matrix2Numbers[a][b].setBackgroundColor(Color.WHITE);
                            }
                        }

                        for (int a = z; a < 6; ++a) {
                            for (int b = y; b < 6; ++b) {
                                matrix2Numbers[a][b].setText("");
                                matrix2Numbers[a][b].setBackgroundColor(Color.WHITE);
                            }
                        }
                    } else {
                        if (z > matrix2MaxX) {
                            matrix2MaxX = z;
                        }
                        if (y > matrix2MaxY) {
                            matrix2MaxY = y;
                        }

                        for (int a = 0; a < matrix2MaxX; ++a) {
                            for (int b = 0; b < matrix2MaxY; ++b) {
                                matrix2Numbers[a][b].setBackgroundColor(Color.BLUE);
                            }
                        }
                    }
                }

                @Override
                public void afterTextChanged(Editable s) {

                }
            });



        }

Answer 1

Check if some other parts of code work with your y and z because you are declaring them outside the loop. There's maybe some piece of code that's modifying them and you are unaware of the side effect.