我試圖在一種方法中捕獲沒有輸入（輸入鍵）和無效輸入除 y/n 之外的所有內容。我嘗試了兩種不同的方式（粘貼），但我無法同時使用“輸入鍵”和“錯誤輸入 y/n”。感謝您的幫助。第一次嘗試：public static String askToContinue(Scanner sc) {String choice = "";boolean isValid = false;while (!isValid){System.out.print("Continue? (y/n): "); if (sc.hasNext()){ choice = sc.next(); isValid = true; } else {System.out.println("Error! " + "This entry is required. Try again"); } if (isValid && !choice.equals("y") || !choice.equals("n")) { System.out.println("Error! Entry must be 'y' or 'n'. Try again"); isValid = false; } } //sc.nextLine(); // discard any other data entered on the line System.out.println(); return choice; } 2nd attempt public static String askToContinue(Scanner sc) { System.out.print("Continue? (y/n): "); String choice; while (true) {choice = sc.next(); //????????????????????????????????????????????????????? if (choice.length() == 0){ System.out.println("Error! " + "This entry is required. Try again"); continue; } if (!(choice.equals("y") || choice.equals("n"))) { System.out.println("Error! Entry must be 'y' or 'n'. Try again"); continue; } break; } sc.nextLine(); // discard any other data entered on the line System.out.println(); return choice; }
2 回答
梵蒂岡之花
TA貢獻1900條經驗 獲得超5個贊
我嘗試了您的代碼的第一次嘗試。我用注釋行進行了解釋，注釋行包含在下面的代碼中，例如；
public static String askToContinue(Scanner sc) {
String choice = "";
boolean isValid = false;
while (!isValid) {
System.out.print("Continue? (y/n): ");
choice = sc.nextLine(); //to reads all line , because this cannot read with empty enter input
isValid = true;
if (choice.isEmpty()) { //this isEmpty for empty enter
System.out.println("Error! "
+ "This entry is required. Try again");
}
System.out.println(choice);
//this logic if not y or n , it will return error
if (!choice.equals("y") && !choice.equals("n")) {
System.out.println("Error! Entry must be 'y' or 'n'. Try again");
isValid = false;
}
}
//sc.nextLine(); // discard any other data entered on the line
System.out.println();
return choice;
}
繁星淼淼
TA貢獻1775條經驗 獲得超11個贊
您在第一種情況下的 if 語句是錯誤的。您正在檢查是否選擇is not equal to 'y' 或 not equal to 'n'將始終為真。
改變
if (isValid && !choice.equals("y") || !choice.equals("n"))到
if (isValid && !choice.equals("y") && !choice.equals("n"))添加回答
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