java编译/捕获异常
我在这个代码上遇到了很多麻烦。在我试图输入代码以捕获异常之前,代码按照预期进行了编译和运行。然后我再也无法编译它了。如果用户输入负数,它将捕获异常并生成错误消息
import java.awt.event.ActionEvent; //Next group of lines import various Java classes
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JCheckBox;
import javax.swing.JPanel;
import javax.swing.JTextField;
import java.awt.GridLayout;
import java.text.*;
import java.io.IOException;
public class SquareRoot extends JFrame
{
public static void main(String[] args) {
//Creates Window
JFrame frame = new JFrame();
frame.setSize(450, 300);
frame.setTitle("Find the Square Root");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JLabel Numberlbl = new JLabel("Enter a number:");
final JTextField NumberField = new JTextField(10);
NumberField.setText("");
JLabel Answerlbl = new JLabel("Square Root of your number is:");
final JTextField AnswerField = new JTextField(10);
AnswerField.setText("");
JLabel ButtonLabel = new JLabel("Calculate Square Root");
JButton button = new JButton("Find Square Root");
JPanel panel = new JPanel();
panel.setLayout(new GridLayout(3,2));
panel.add(Numberlbl);
panel.add(NumberField);
panel.add(ButtonLabel);
panel.add(button);
panel.add(Answerlbl);
panel.add(AnswerField);
frame.add(panel);
class CalculateListener implements ActionListener {
public void actionPerformed(ActionEvent event) {
double NumberX = Double.parseDouble(NumberField.getText());
try
{
if(NumberX >=0);
}
catch(IOException e)
{
System.out.println("Number can not be negative.");
}
double Answer = Math.sqrt(NumberX);
AnswerField.setText(String.valueOf(Answer));
}
}
ActionListener listener = new CalculateListener();
button.addActionListener(listener);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
# 1 楼答案
最好使用:
# 2 楼答案
抛出自定义异常
# 3 楼答案
你不需要试着捕捉来检查负片,下面就足够了。但在格式化时,您可能需要尝试捕获
# 4 楼答案
Netbeans说“异常java.io.IOException从不在相应的if语句中抛出”
基本上如果语句不抛出异常
# 5 楼答案
它运转良好