为什么我的计算器不返回负值？

Question

每次我尝试在文本字段中打印一个负数时，它总是打印0。我想不出原因，因为每当我使用调试器时，它都会显示sum存储一个负数。只要其他运算符不是负数，它们都将返回正确的数字。我还在程序中使用javafx。

谢谢！

    public class Calculator extends Application implements EventHandler<ActionEvent> {

    Button[] numpadButtons = new Button[10];
    Button[] operatorButtons = new Button[6];
    String[] numButtonNames = {"1", "2", "3", "4", "5", "6", "7", "8", "9", "0"};
    String[] operatorButtonNames = {"+", "-", "x", "/", "=", "C"};
    TextField label;
    String input = "";
    int sum = 0;
    int num1 = 0;
    int num2 = 0;
    char operator = ' ';
    int numOperators = 0;

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        GridPane gPane = new GridPane();
        BorderPane bPane = new BorderPane();

        label = new TextField();

        label.setEditable(false);

        Scene scene = new Scene(bPane, 300, 400);

        primaryStage.setScene(scene);
        primaryStage.show();

    }

    @Override
    public void handle(ActionEvent event) {
        try {
            if (event.getSource() == numpadButtons[0]) {
                input += "1";
                label.setText(input);
            } else if (event.getSource() == numpadButtons[1]) {
                input += "2";
                label.setText(input);
            } else if (event.getSource() == numpadButtons[2]) {
                input += "3";
                label.setText(input);
            } else if (event.getSource() == numpadButtons[3]) {
                input += "4";
                label.setText(input);
            } else if (event.getSource() == numpadButtons[4]) {
                input += "5";
                label.setText(input);
            } else if (event.getSource() == numpadButtons[5]) {
                input += "6";
                label.setText(input);
            } else if (event.getSource() == numpadButtons[6]) {
                input += "7";
                label.setText(input);
            } else if (event.getSource() == numpadButtons[7]) {
                input += "8";
                label.setText(input);
            } else if (event.getSource() == numpadButtons[8]) {
                input += "9";
                label.setText(input);
            } else if (event.getSource() == numpadButtons[9]) {
                input += "0";
                label.setText(input);
            } else if (event.getSource() == operatorButtons[4]) {
                if (numOperators == 1) {
                    parseInput();
                    calculate();
                    label.setText(Integer.toString(sum));
                    clearNums();
                    sum = 0;
                } else if (numOperators == 0) {
                    throw new ArithmeticException("No operator detected");
                } else {
                    throw new ArithmeticException("Unknown error");
                }

            } else if (event.getSource() == operatorButtons[0]) {
                input += "+";
                ++numOperators;
                operator = '+';
                label.setText(input);
            } else if (event.getSource() == operatorButtons[1]) {
                input += "-";
                ++numOperators;
                operator = '-';
                label.setText(input);
            } else if (event.getSource() == operatorButtons[2]) {
                input += "x";
                ++numOperators;
                operator = 'x';
                label.setText(input);
            } else if (event.getSource() == operatorButtons[3]) {
                input += "/";
                ++numOperators;
                operator = '/';
                label.setText(input);
            } else if (event.getSource() == operatorButtons[5]) {
                clearNums();
                clearScreen();
                sum = 0;
            } 


        } catch (ArithmeticException e) {
            clearNums();
            clearScreen();
            sum = 0;
            label.setText(e.getMessage());
        }
    }

    public void calculate() throws ArithmeticException {
        if (operator == 47) {//if operator is a forward slash
            if (num2 != 0) {
                sum = (num1 / num2);
            } else {
                throw new ArithmeticException("Arithmetic error");
            }
        } else if (operator == 61) { // -
            sum = (num1 - num2);
        } else if (operator == 43) { //+
            sum = (num1 + num2);
        } else if (operator == 120) {
            sum = (num1 * num2);
        }

    }

    public void parseInput() {
        int indexOfOperator = input.indexOf(operator);
        int inputLength = input.length();
        num1 = Integer.parseInt(input.substring(0, indexOfOperator));
        num2 = Integer.parseInt(input.substring(indexOfOperator + 1, inputLength));

    }




}

Answer 1

-的值为45。试试这个。

public void calculate() throws ArithmeticException {
        System.out.println((int)operator);
        if (operator == 47) {// if operator is a forward slash
            if (num2 != 0) {
                sum = (num1 / num2);
            } else {
                throw new ArithmeticException("Arithmetic error");
            }
        } else if (operator == 45) { // -
            sum = (num1 - num2);
        } else if (operator == 43) { // +
            sum = (num1 + num2);
        } else if (operator == 120) {
            sum = (num1 * num2);
        }

    }