我正在申请数学练习。它是循环10个随机问题，并具有计数器来显示您有多少对错和多少错了。
我试图进行一些异常处理，以便在没有输入任何值时弹出一个弹出窗口。当弹出窗口出现时，错误答案计数器或正确答案计数器的计数器无论如何都会递增。
这是代码：
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
@SuppressWarnings("serial")
public class MathPractice extends JFrame {
Container c;
JPanel output;
JLabel title, num1, num2, lbloperator, equals, mark, display, correct, wrong ,correctN, wrongN;
JTextField answer;
JButton newB, ansB;
JTextArea txtdisplay;
String operator;
int number1;int number2;int rightNum = 0;int wrongNum = 0;int result;int random;int randomOperator; int cnt = 1;
public int getRandom(){
int random = (int)(Math.random() * 10 + 1);
return random;
}
public String getRandomOperator(){
int randomOperator = (int)(Math.random() * 4 + 1);
if(randomOperator == 1)
return "+";
else if (randomOperator == 2)
return "-";
else if (randomOperator == 3)
return "*";
else {
return "/";
}
}
class ExcerciseHandler implements ActionListener {
public void actionPerformed(ActionEvent e) {
number1 = getRandom();
number2 = getRandom();
num1.setText(""+number1);
num2.setText(""+number2);
operator = getRandomOperator();
lbloperator.setText(operator);
rightNum = 0;
wrongNum = 0;
cnt = 1;
correctN.setText("" + rightNum);
wrongN.setText("" + wrongNum);
display.setText("");
answer.setText("");
}
}
class AnswerHandler implements ActionListener {
public void actionPerformed(ActionEvent e) {
boolean canRun = true;
double input = 0;
try{
input = Double.parseDouble(answer.getText());
}
catch (Exception ex){
canRun = false;
JOptionPane.showMessageDialog(null, "Please enter a valid number!");
answer.requestFocus();
answer.selectAll();
}
operator = lbloperator.getText();
if(cnt <= 10){
if (operator.equals("+")){
result = number1 + number2;
if(input == result){
rightNum++;
correctN.setText(""+rightNum);
}
else {
wrongNum++;
wrongN.setText(""+wrongNum);
}
}
else if (operator.equals("-")){
result = number1 - number2;
if(input == result){
rightNum++;
correctN.setText(""+rightNum);
}
else {
wrongNum++;
wrongN.setText(""+wrongNum);
}
}
else if (operator.equals("*")){
result = number1 * number2;
if(input == result){
rightNum++;
correctN.setText(""+rightNum);
}
else {
wrongNum++;
wrongN.setText(""+wrongNum);
}
}
else {
result = number1 / number2;
if(input == result){
rightNum++;
correctN.setText(""+rightNum);
}
else {
wrongNum++;
wrongN.setText(""+wrongNum);
}
}
number1 = getRandom();
number2 = getRandom();
num1.setText(""+number1);
num2.setText(""+number2);
lbloperator.setText("" + getRandomOperator());
answer.setText("");
answer.requestFocus();
cnt++;
}
if (cnt == 11 && rightNum > 6){
display.setText("Keep up the good work!");
}
else if (cnt == 11 && rightNum <= 6){
display.setText("Better luck next time!");
}
}
}
Font f = new Font("Arial", Font.BOLD, 20);
Font numbers = new Font("Arial", Font.PLAIN, 30);
Font operators = new Font("Arial", Font.PLAIN, 20);
Font outputF = new Font("Arial", Font.ITALIC, 15);
Font fAnswers = new Font("Arial", Font.BOLD, 30);
MathPractice (){
super("Math Practice");
c = getContentPane();
c.setLayout(null);
//c.setBackground(Color.blue);
title = new JLabel("How Much is: ");
title.setSize(150,20);
title.setLocation(130, 5);
title.setFont(f);
title.setForeground(Color.red);
number1 = getRandom();
num1 = new JLabel(""+ number1);
num1.setSize(40, 40);
num1.setLocation(30, 35);
num1.setFont(numbers);
lbloperator = new JLabel(getRandomOperator());
lbloperator.setSize(40, 40);
lbloperator.setLocation(85, 37);
lbloperator.setFont(operators);
number2 = getRandom();
num2 = new JLabel(""+ number2);
num2.setSize(40, 40);
num2.setLocation(140, 35);
num2.setFont(numbers);
equals = new JLabel(" = ");
equals.setSize(40, 40);
equals.setLocation(200, 35);
equals.setFont(numbers);
answer = new JTextField(8);
answer.setSize(80, 40);
answer.setLocation(250, 35);
answer.setFont(numbers);
mark = new JLabel("?");
mark.setSize(40, 40);
mark.setLocation(350, 35);
mark.setFont(numbers);
display = new JLabel("");
display.setSize(350, 40);
display.setLocation(30, 90);
display.setFont(numbers);
//display.setVisible(false);
newB = new JButton(" New Excercise ");
newB.setSize(170, 40);
newB.setLocation(15, 170);
ExcerciseHandler eh = new ExcerciseHandler();
newB.addActionListener(eh);
ansB = new JButton(" Answer ");
ansB.setSize(170, 40);
ansB.setLocation(195,170);
AnswerHandler ah = new AnswerHandler();
ansB.addActionListener(ah);
output = new JPanel();
output.setLayout(null);
output.setSize(375, 225);
output.setBorder(BorderFactory.createTitledBorder("Statistic: "));
output.setLocation(5, 225);
correct = new JLabel("<html> Number of Correct\n Answers: " );
correct.setSize(150, 50);
correct.setLocation(15, 25);
correct.setFont(outputF);
wrong = new JLabel("<html> Number of Wrong\n Answers: ");
wrong.setSize(150, 50);
wrong.setLocation(230, 25);
wrong.setFont(outputF);
correctN = new JLabel("" + rightNum);
correctN.setSize(100, 100);
correctN.setLocation(60, 50);
correctN.setFont(fAnswers);
correctN.setForeground(Color.green);
wrongN = new JLabel("" + wrongNum);
wrongN.setSize(100, 100);
wrongN.setLocation(275, 50);
wrongN.setFont(fAnswers);
wrongN.setForeground(Color.red);
c.add(title);c.add(num1);c.add(lbloperator);c.add(num2);c.add(equals);c.add(answer);c.add(mark);c.add(display);c.add(newB);
c.add(ansB);c.add(output);
output.add(correct);output.add(wrong);output.add(correctN);output.add(wrongN);
}
public static void main(String[] args) {
MathPractice app = new MathPractice();
app.setSize(400, 500);
app.setVisible(true);
app.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
}
}
最佳答案
在catch块的底部放置一个return;语句。当发生异常时，这将导致您的代码在处理异常后离开处理程序。
try{
input = Double.parseDouble(answer.getText());
}
catch (NumberFormatException ex){
canRun = false;
JOptionPane.showMessageDialog(null, "Please enter a valid number!");
answer.requestFocus();
answer.selectAll();
return; // ****** added *****
}
顺便说一句：您应该避免捕获
Exception，而应该只捕获特定的异常，这里是NumberFormatException。