Question

很抱歉提出愚蠢的问题，但我没想到。我希望重复if else语句，直到获得有效输入然后继续询问下一个问题。任何人都可以告诉我什么是错的？代码本身没有任何问题（它可以运行）但它只显示＆＃34;错误＆＃34;和＃34;请重新输入答案＆＃34;然后在没有询问＆＃34; day＆＃34;的情况下进入下一部分。再次。提前致谢

public class Test {

    public static void main(String[] args) {
        String Day; // The user’s name.
        TextIO.put("This program is to tell you what to eat for today.");
        TextIO.put("\nBefore it starts, can you tell me what's the day today?");

        Day = TextIO.getln();{

        if (Day.equals("Monday")){
            System.out.print("Eat Chocolates");
        }
        else if (Day.equals("Tuesday")){
            System.out.print("Eat Oranges");
        }
        else if (Day.equals("Wednesday")){
            System.out.print("Eat Strawberries");
        }
        else if (Day.equals("Thursday")){
            System.out.print("Eat Lemons");
        }
        else if (Day.equals("Friday")){
            System.out.print("Eat Bananas");
        }
        else if (Day.equals("Saturday")){
            System.out.print("Eat Apples");
        }
        else if (Day.equals("Sunday")){
            System.out.print("Eat Grass");
        }

        else if (Day.equals(false))
        {System.out.print("Error");
        System.out.print("\nPlease re-eneter the answer");
        Day = TextIO.getln();

        }

Answer 1

最好在多个if：

中使用switch语句

boolean error=false;
    do{
        error=false;
        String day="";
        switch (day) {
        case "Monday":
            System.out.print("Eat Chocolates");
            break;
        case "Tuesday":
            System.out.print("Eat Oranges");
            break;
            .
            .
            .
        default:
            System.out.print("Error");
            System.out.print("\nPlease re-eneter the answer");
            error=true;
            break;
        }
    }
    while(error)

Answer 2

您应该在while中查看do-while或Java。

您可以从以下示例中获得想法..

boolean status = true;   
String input = "";
while (status) {
 System.out.println("your input\n");
 input = new Scanner(System.in).nextLine();
 if (input.equals("valid")) {
    System.out.println("valid input");
    status = false;
 } else {
    // not a valid input
    System.out.println("Please re-try");
 }
}

Answer 3

试试这个：

String day = TextIO.getln();
List<String> daysOfWeek = new ArrayList<String>(Arrays.asList("Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"));
while (!daysOfWeek.contains(day)) {
    System.out.println("Invalid input.");
    day = TextIO.getln();
}
... continue with program after valid input ...

Answer 4

我从这里找到了一个TextIO课程：http://math.hws.edu/javanotes/source/

然后我编辑了你的代码，看起来像这样......

public class Test {

    public static void main(String[] args) {
        String Day; // The user’s name.
        TextIO.put("This program is to tell you what to eat for today.");
        TextIO.put("\nBefore it starts, can you tell me what's the day today?");

        Day = TextIO.getln();

        if (Day.equals("Monday")){
            System.out.print("Eat Chocolates");
        }
        else if (Day.equals("Tuesday")){
            System.out.print("Eat Oranges");
        }
        else if (Day.equals("Wednesday")){
            System.out.print("Eat Strawberries");
        }
        else if (Day.equals("Thursday")){
            System.out.print("Eat Lemons");
        }
        else if (Day.equals("Friday")){
            System.out.print("Eat Bananas");
        }
        else if (Day.equals("Saturday")){
        System.out.print("Eat Apples");
        }
        else if (Day.equals("Sunday")){
            System.out.print("Eat Grass");
        }
        else if (Day.equals(false))
        {System.out.print("Error");
        System.out.print("\nPlease re-eneter the answer");
        Day = TextIO.getln();

        }
}

}

最后我运行了这段代码并得到了这个......

$ java Test
This program is to tell you what to eat for today.
Before it starts, can you tell me what's the day today?Monday
Eat Chocolates

Answer 5

使用Java OOD Concepts并为this创建递归方法的最佳方法。并且switch语句比if else梯形图更合适。你可以通过以下[1]更好地了解java中的递归方法。只需将您的程序更改为：

    public class Test {


        public Test() {

        }


        public void getInput() {
             String Day; // The user’s name.
                TextIO.put("This program is to tell you what to eat for today.");
                TextIO.put("\nBefore it starts, can you tell me what's the day today?");
         String day=TextIO.getln();
            switch (day) {
            case "Monday":
                System.out.print("Eat Chocolates");
                break;
            case "Tuesday":
                System.out.print("Eat Oranges");
                break;
                .
                .
                .
            default:
                System.out.print("Error");
                System.out.print("\nPlease re-eneter the answer");
               getInput();
            }
            }



        public static void main(String[] args) {
                Test test = new Test();
                test.getInput();
         }
   }

[1]。 http://danzig.jct.ac.il/java_class/recursion.html

希望这会对你有所帮助。

Answer 6

使用循环

public static void main(String[] args) {
        String Day; // The user’s name.
        TextIO.put("This program is to tell you what to eat for today.");
        TextIO.put("\nBefore it starts, can you tell me what's the day today?");

        do
        {
        Day = TextIO.getln();

        if (Day.equals("Monday")){
            System.out.print("Eat Chocolates");
            break;
        }
        else if (Day.equals("Tuesday")){
            System.out.print("Eat Oranges");
            break;
        }
        else if (Day.equals("Wednesday")){
            System.out.print("Eat Strawberries");
            break;
        }
        else if (Day.equals("Thursday")){
            System.out.print("Eat Lemons");
            break;
        }
        else if (Day.equals("Friday")){
            System.out.print("Eat Bananas");
            break;
        }
        else if (Day.equals("Saturday")){
            System.out.print("Eat Apples");
            break;
        }
        else if (Day.equals("Sunday")){
            System.out.print("Eat Grass");
            break;
        }

        else if (Day.equals(false))
        {System.out.print("Error");
        System.out.print("\nPlease re-eneter the answer");
        }
     }while(true);
 }

重复if else语句

6 个答案: