java - 计算器算法

Question

我正在尝试创建一个可以执行简单运算的计算器，并且您应该能够拥有多个值和不同的运算符。它还没有完成，所以稍后会改进，但现在我对执行计算的方法有问题。

在我发布相关代码之前。另一部分只是 Swing 对象实例化。

    private class OperatorListener implements ActionListener{

    public void actionPerformed(ActionEvent e){
        if(e.getSource()== resetButton){
            Operators.clear();
            Numbers.clear();
            actualNumber.setText("");
            previousNumbers.setText("");
        } else if(e.getSource() == sumButton){
            Numbers.add(new Double(actualNumber.getText()));
            Double Result = performCalculation(Numbers, Operators);
            actualNumber.setText(String.valueOf(Result));
            previousNumbers.setText("");
        } else if(e.getSource() == sqrtButton){

        } else {
            /*
             * The operator numbers handlers. When a operator
             * button is clicked the number in the lower JTF
             * is parsed to Double value and added to Numbers
             * list. Operator added to Operators list. Lower
             * JTF is cleared.*/
            Numbers.add(new Double(actualNumber.getText()));
            Operators.add(e.getActionCommand());
            String currentPriovusNumbers = previousNumbers.getText();
            previousNumbers.setText(currentPriovusNumbers + " " + actualNumber.getText() + " " + e.getActionCommand());
            actualNumber.setText("");
        }
    }
}

    private double performCalculation(ArrayList<Double> Numbers, ArrayList<String> Operators){
    double result = Numbers.get(0);
    for(int index = 0; index < Numbers.size(); index++){
        switch(Operators.get(index)){
            case "+":
                result += Numbers.get(index + 1);
                break;
            case "-":
                result -= Numbers.get(index + 1);
                break;
            case "/":
                result /= Numbers.get(index + 1);
                break;
            case "*":
                result *= Numbers.get(index + 1);
                break;
            case "%":
                result %= Numbers.get(index + 1);
                break;
        }
    }
    return result;
}

我收到的错误是这样的:

Exception in thread "AWT-EventQueue-0" java.lang.IndexOutOfBoundsException: Index: 1, Size: 1
at java.util.ArrayList.rangeCheck(ArrayList.java:604)
at java.util.ArrayList.get(ArrayList.java:382)
at com.calculatorSwing.business.Calculator.performCalculation(Calculator.java:146)
at com.calculatorSwing.business.Calculator.access$6(Calculator.java:143)

第 146 行是第一个 switch case 语句，它让我知道不存在我尝试访问的索引，但我检查了运算符列表，发现元素 0 内有一个“+”。问题是什么？

Answer 1

更改 performCalculation 方法的 for 循环。

来自:

 for(int index = 1; index <= Numbers.size(); index++)

致:

for(int index = 1; index < Numbers.size(); index++)

根据您的 for loop 下面的 ArrayList get 将出现异常。

Numbers.get(Numbers.size());// will generate IndexOutOfBoundsException.