我正在嘗試設置一些 if 語句，以確保用戶輸入不會超出我設置的范圍（如果我希望 if 語句將它們返回到主代碼的開頭）。String animal = JOptionPane.showInputDialog("Enter In Animal Name"); // Asking for user to enter a animalString fruit = JOptionPane.showInputDialog("Enter In A Fruit Name"); // Asking user to enter a fruitint days = Integer.parseInt(JOptionPane.showInputDialog("Enter In How Many Days Between 1 And 10"));// Above integer is asking the user to enter the amount of days.// Below if statements are basically error checking to ensure the user stays between the// range asked for when they are asked to enter in days between 1 and 10.if (days <= 0) { // Ensures that negative numbers cannot be entered. JOptionPane.showMessageDialog(null, "Error, Please enter a number between 1 and 10"); return;}if (days >= 10) { // Ensures nothing over 10 can be entered. JOptionPane.showMessageDialog(null, "Error, Please enter a number between 1 and 10"); return;}如果 if 語句說它是一個錯誤，它應該返回要求他們重新輸入天數
4 回答
冉冉說
TA貢獻1877條經驗 獲得超1個贊
使用do-while至少執行一次的循環，如果days不滿足條件則每次都循環回來。
public static void main(String[] args)
{
do {
//Your other code
String animal = JOptionPane.showInputDialog("Enter In Animal Name"); // Asking for user to enter a animal
String fruit = JOptionPane.showInputDialog("Enter In A Fruit Name"); // Asking user to enter a fruit
int days = askForInput();
if (days <= 0 || days >= 10) { // Ensures that negative numbers cannot be entered.
JOptionPane.showMessageDialog(null, "Error, Please enter a number between 1 and 10");
}
} while (days <= 0 || days >= 10);
}
//Pass whatever parameters you might need
public static int askForInput() {
int days = Integer.parseInt(JOptionPane.showInputDialog("Enter In How Many Days Between 1 And 10"));
//Any other code you want
return days;
}
我還將它提取到一個方法中，這可能是不必要的，但如果需要，它可以讓您添加更多功能。
如果您不想每次都被問到這個問題，您也可以移動animal或fruit離開。do
哆啦的時光機
TA貢獻1779條經驗 獲得超6個贊
允許代碼重新啟動代碼塊（即返回到開頭并重試）的一種方法是使用帶有“永遠”循環的continueand語句。break
for (;;) { // loop forever
// some code here
if (failure condition 1) {
// handle failure here
continue; // go back and try again
}
if (failure condition 2) {
// handle failure here
continue; // go back and try again
}
// more code and failure condition checks here
break; // unconditional exit loop, since all is ok
}
如果“此處的某些代碼”本身位于循環內，但需要返回到開頭并重試，則可以為此使用標簽：
TRYAGAIN: for (;;) { // loop forever
// some code here
for (some looping here) {
// some code here
try {
if (failure condition) {
// handle failure here
continue TRYAGAIN; // go back and try again
}
} finally {
// code here will execute, even if 'continue' is used
}
}
// more code and failure condition checks here
break; // unconditional exit loop, since all is ok
}
吃雞游戲
TA貢獻1829條經驗 獲得超7個贊
String animal;
String fruit;
int days = 0;
animal = JOptionPane.showInputDialog("Enter In Animal Name");
fruit = JOptionPane.showInputDialog("Enter In A Fruit Name");
while(days <= 0 || days > 10) {
days = Integer.parseInt(JOptionPane.showInputDialog("Enter In How Many Days Between 1 And 10"));
if (days <= 0 || days > 10) {
JOptionPane.showMessageDialog(null, "Error, Please enter a number between 1 and 10");
}
}
臨摹微笑
TA貢獻1982條經驗 獲得超2個贊
使用 while 循環
// Your user prompt for animal and fruit goes here
boolean exit = false;
while(!exit)
{
// Your user prompt for days code goes here
if (days <= 0 || days > 10) {
JOptionPane.showMessageDialog(null, "Error, Please enter a number between 1 and 10");
exit = false; // This is not necessary but nice for readability's sake
}
else {
exit = true;
}
}
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