Question

我是Uni的学生并且正在编程。我们必须使用java制作一个计算器，其中一个要点是输入一个消息＆＃34;不是数字＆＃34;当用户除以零时。通常情况下，它会显示＆＃34; Infinity＆＃34;，因此任务是更改该消息，但是我还没有去理解如何做到这一点。如果有人有想法或者可以帮我改写，请在这里发表评论。谢谢！

public void getResult() {

double result = 0;

temporary[1] = Double.parseDouble(display.getText());

String temp0 = Double.toString(temporary[0]);

String temp1 = Double.toString(temporary[1]);

  try {
    if(function[2] == true)
      result = temporary[0] * temporary[1];

    else if(function[3] == true)
      result = temporary[0] / temporary[1];

    else if(function[0] == true)
      result = temporary[0] + temporary [1];

    else if(function[1] == true)
      result = temporary[0] - temporary[1];        
    display.setText(Double.toString(result));

    for(int i=0; i<4; i++)
      function[i] = false;
    } catch(NumberFormatException e) {}
}



public void actionPerformed(ActionEvent ae) {
if(ae.getSource() == button[0])
  display.append("1");
if(ae.getSource() == button[1])
  display.append("2");
if(ae.getSource() == button[2])
  display.append("3");
if(ae.getSource() == button[3]) {
  temporary[0] = Double.parseDouble(display.getText());
  function[0] = true;
  display.setText("");
}
if(ae.getSource() == button[4])
  display.append("4");
if(ae.getSource() == button[5])
  display.append("5");
if(ae.getSource() == button[6])
  display.append("6");
if(ae.getSource() == button[7]) {
  temporary[0] = Double.parseDouble(display.getText());
  function[1] = true;
  display.setText("");
}
if(ae.getSource() == button[8])
  display.append("7");
if(ae.getSource() == button[9])
  display.append("8");
if(ae.getSource() == button[10])
  display.append("9");
if(ae.getSource() == button[11]) {
  temporary[0] = Double.parseDouble(display.getText());
  function[2] = true;
  display.setText("");
}
if(ae.getSource() == button[12])
  display.append("0");
if(ae.getSource() == button[13])
  display.append(".");
if(ae.getSource() == button[14])
  clear();
if(ae.getSource() == button[15]){
  temporary[0] = Double.parseDouble(display.getText());
  function[3] = true;
  display.setText("");
}
if(ae.getSource() == button[16])
  getResult();
}

public static void main(String[] arguments) {
    Calculator c = new Calculator();
}
}

Answer 1

如你所知，除以零是无穷大。在java中，如果对原始包装类除以零则没有错误。例如

public static void main(String[] args) {
    Double a = 1.0;
    Double b = 0.0;

    Double c = a/b;
    c.isInfinite();
    System.out.println(c.toString());
}

打印：

Infinity

所以，只需将结果形式double改为Double，然后：

public void getResult() {
    Double result = 0;
    temporary[1] = Double.parseDouble(display.getText());
    String temp0 = Double.toString(temporary[0]);
    String temp1 = Double.toString(temporary[1]);
    try {
        if (function[2] == true)
            result = temporary[0] * temporary[1];

        else if (function[3] == true)
            result = temporary[0] / temporary[1];

        else if (function[0] == true)
            result = temporary[0] + temporary[1];

        else if (function[1] == true)
            result = temporary[0] - temporary[1];

        if(c.isInfinite() || c.isNaN()) {
            display.setText("Not a number");
        } else {
            display.setText(result.toString());
        }
        for (int i = 0; i < 4; i++)
            function[i] = false;
    } catch (NumberFormatException e) {
        display.setText(e.getMessage());
    }
}

Java计算器ActionListener。如何更改消息＆＃34; Infinity＆＃34;什么时候除以零？

1 个答案: