Java中的while循環問題

Question

我的 while 循環有問題。 第三次執行后，它不會接受用戶輸入，它只輸出“輸入您的名字”。 我嘗試了多種方法，但它們似乎不起作用。 循環應繼續運行，直到用戶輸入“否”為止。

我知道我很接近了！

System.out.print("Would you like to enter another patient? Type Yes or No: ");
String userInput = input.nextLine();
if (userInput.equals("Yes")) 
{
    while (userInput.equals("Yes")) 
    {
        System.out.print("Enter your first name: ");
        String firstName2 = input.nextLine();
        System.out.print("Enter your last name: ");
        String lastName2 = input.nextLine();
        System.out.print("Enter your address: ");
        String address2 = input.nextLine();
        System.out.print("Enter your city: ");
        String city2 = input.nextLine();
        System.out.print("Enter your state: ");
        String state2 = input.nextLine();
        System.out.print("Enter your zip code + 4: ");
        String zip2 = input.nextLine();
        System.out.print("Enter amount owed: ");
        String amount2 = input.nextLine();
        System.out.print("Enter your payment amount: ");
        String payment2 = input.nextLine();
        System.out.print("Enter the date of payment: ");
        String date2 = input.nextLine();
        System.out.println("\t\t\t\t\t" + "XYZ Hospital");
        System.out.println();
        System.out.println("Name Information" + "\t\t\t\t" + "Address" + "\t\t\t\t\t\t" + "Payment");
        System.out.println();
        System.out.println("Last" + "\t" + "First" + "\t\t\t" + "Address Line 1" + "\t" + "City" + "\t" + "State" + "\t" + "Zip" + "\t" + "Amount Owed" + "\t" + "Payment Amount" + "\t" + "Payment Date");
        System.out.println();
        System.out.println(lastName2 + " " + firstName2 + "\t" + address2 + " " + city2 + ", " + state2 + " " + zip2 + "\t" + amount2 + "\t\t" + payment2 + "\t\t" + date2);
        System.out.print("Would you like to enter another patient? Type Yes or No: ");
    }
}
else if (userInput.equals("No")) 
{
    System.out.println("Goodbye");
}

Answer 1

對於這些類型的程序，您可以使用 do-while 循環。 第一次無條件運行，然后您可以在 userInput 變量中從用戶獲取輸入。

String userInput;
 do{
    System.out.print("Enter your first name: ");
    String firstName2 = input.nextLine();
    System.out.print("Enter your last name: ");
    String lastName2 = input.nextLine();
    System.out.print("Enter your address: ");
    String address2 = input.nextLine();
    System.out.print("Enter your city: ");
    String city2 = input.nextLine();
    System.out.print("Enter your state: ");
    String state2 = input.nextLine();
    System.out.print("Enter your zip code + 4: ");
    String zip2 = input.nextLine();
    System.out.print("Enter amount owed: ");
    String amount2 = input.nextLine();
    System.out.print("Enter your payment amount: ");
    String payment2 = input.nextLine();
    System.out.print("Enter the date of payment: ");
    String date2 = input.nextLine();
    System.out.println("\t\t\t\t\t" + "XYZ Hospital");
    System.out.println();
    System.out.println("Name Information" + "\t\t\t\t" + "Address" + "\t\t\t\t\t\t" + "Payment");
    System.out.println();
    System.out.println("Last" + "\t" + "First" + "\t\t\t" + "Address Line 1" + "\t" + "City" + "\t" + "State" + "\t" + "Zip" + "\t" + "Amount Owed" + "\t" + "Payment Amount" + "\t" + "Payment Date");
    System.out.println();
    System.out.println(lastName2 + " " + firstName2 + "\t" + address2 + " " + city2 + ", " + state2 + " " + zip2 + "\t" + amount2 + "\t\t" + payment2 + "\t\t" + date2);
    System.out.print("Would you like to enter another patient? Type Yes or No: ");
    userInput = input.nextLine();

}while (userInput.equals("Yes"));

Answer 2

我認為問題在於您在 if 語句中執行 while 循環。 嘗試在循環中插入 if ，如下所示：

    Scanner input=new Scanner(System.in);
    System.out.println("enter details");
    String answer=input.next();
    while(answer.equals("yes")) {
        if(answer.equals("yes")) {
System.out.println("name");
String name=input.next();
System.out.println("last name");
String last=input.next();
System.out.println("enter details");
     answer=input.next();    
} }

System.out.println("bye");

    }

Answer 3

你永遠不會離開你的循環，因為userInput只在循環之前設置一次並且永遠不會在循環內設置，這意味着你永遠不會改變while條件。

System.out.print("Would you like to enter another patient? Type Yes or No: ");
String userInput = input.nextLine();
if (userInput.equals("Yes")) {
    while (userInput.equals("Yes")) {
        //your data entry...

        System.out.print("Would you like to enter another patient? Type Yes or No: ");
        // change userInput here, else, you're never going out of the loop.
        // so add this
        userInput = input.nextLine();
    }
} else if (userInput.equals("No")) {
    System.out.println("Goodbye");
}

雖然，您的解決方案可能更適合您的這種格式的需求：

System.out.print("Would you like to enter another patient? Type Yes or No: ");
String userInput = input.nextLine();
while (userInput.equals("Yes")) {
    //your data entry...

    System.out.print("Would you like to enter another patient? Type Yes or No: ");
    userInput = input.nextLine();
}

System.out.println("Goodbye");

這樣，當用戶輸入“是”時，您將進入循環並在他輸入其他內容時退出。 如果用戶從一開始就輸入了“是”以外的其他內容，您將永遠不會進入循環並立即關閉應用程序。

Answer 4

工作代碼：請檢查代碼

import java.util.Scanner;

public class temp {
    static String userInput;
    private static Scanner input;

    public static void main(String[] args) {
        input = new Scanner(System.in); 

        System.out
                .print("Would you like to enter another patient? Type Yes or No:  ");
        userInput = input.nextLine();

        while (userInput.equals("Yes")) { //while loop will iterate till "userInput is equals to Yes"
            System.out.print("Enter your first name: ");
            String firstName2 = input.nextLine();
            System.out.print("Enter your last name: ");
            String lastName2 = input.nextLine();
            System.out.print("Enter your address: ");
            String address2 = input.nextLine();
            System.out.print("Enter your city: ");
            String city2 = input.nextLine();
            System.out.print("Enter your state: ");
            String state2 = input.nextLine();
            System.out.print("Enter your zip code + 4: ");
            String zip2 = input.nextLine();
            System.out.print("Enter amount owed: ");
            String amount2 = input.nextLine();
            System.out.print("Enter your payment amount: ");
            String payment2 = input.nextLine();
            System.out.print("Enter the date of payment: ");
            String date2 = input.nextLine();
            System.out.println("\t\t\t\t\t" + "XYZ Hospital");
            System.out.println();
            System.out.println("Name Information" + "\t\t\t\t" + "Address"
                    + "\t\t\t\t\t\t" + "Payment");
            System.out.println();
            System.out.println("Last" + "\t" + "First" + "\t\t\t"
                    + "Address Line 1" + "\t" + "City" + "\t" + "State" + "\t"
                    + "Zip" + "\t" + "Amount Owed" + "\t" + "Payment Amount"
                    + "\t" + "Payment Date");
            System.out.println();
            System.out.println(lastName2 + " " + firstName2 + "\t" + address2
                    + " " + city2 + ", " + state2 + " " + zip2 + "\t" + amount2
                    + "\t\t" + payment2 + "\t\t" + date2);
            System.out
                    .print("Would you like to enter another patient? Type Yes or No: \n");
            userInput = input.nextLine(); // Taking user choice for "Yes" or "No"

            if (userInput.equals("No")) {
                break; // will Exit loop when user enter "No"
            }
        }

        if (userInput.equals("No")) {
            System.out.println("Goodbye");
        } else {
            System.out.println(" Invalid input :("); // will print when user enter anything other than "Yes" or "No"

        }
    }
}

一旦您在 while 循環內完成從用戶那里獲取數據，您就不會再次從用戶那里獲取輸入。 另請查看代碼注釋以獲取更多信息。

Answer 5

嗯，最大的問題是在第一次檢查后你永遠不會改變 userInput 的值。 所以無論他們在循環結束時輸入“是”還是“否”，它都會繼續循環。 當您詢問他們是否想輸入另一名患者時，您甚至從未讓用戶選擇在循環結束時輸入任何內容。 其次，您可能應該檢查他們是否使用降低功能輸入了“是，是，是，是，y”