java如何做，边做边循环这段代码？

Question

我有以下java代码：

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

    int value = 0;
    String name;
    int age;



        System.out.print("Hey, what's your name? ");
        name = keyboard.next();
        System.out.println();

        System.out.print("Ok, " + name + ", how old are you? ");
        age = keyboard.nextInt();
        System.out.println();

           do{
            if(age < 16){
            System.out.println("You can't visit in the museum, " + name + ".");

            if(age < 18);
                 System.out.println("You can't visit in the park, " + name + ".");
            }
            if (age < 25){
                System.out.println("You can't visit if you have a car, " + name + ".");
            }
            if (age >= 25){
                System.out.println("You can do anything, " + 
                    name + ".");

            }
            while(age > 300);
            System.out.println("It's not correct..Try Again, " + name + 
             ".");


            }
}

我需要用户写出错误的答案，他会再次得到问题“你多大了？”，等他再试一次。。 我要做什么？ 谢谢你的帮助！！：）

Answer 1

Onewhile块不正确，您必须使用：

System.out.println("It's not correct..Try Again, " + name + ".");

do {
    if (age < 16) {
        System.out.println("You can't visit in the museum, " + name + ".");

        if (age < 18);
        System.out.println("You can't visit in the park, " + name + ".");
    }
    if (age < 25) {
        System.out.println("You can't visit if you have a car, " + name + ".");
    }
    if (age >= 25) {
        System.out.println("You can do anything, "
                + name + ".");

    }
    //while(age > 300);<<     wrong position 

    System.out.println("It's not correct..Try Again, " + name + ".");

} while (age > 300);//<<     correct position 

两个

虽然接缝条件不正确，但您必须检查最小和最大年龄，而不仅仅是最大年龄，因此您可以使用：

 while (age < minAge || age > maxAge );

因此，如果年龄小于最小值或最大值，则再次重复最大值

三个这个如果永远不会执行：

if (age < 18);//<<        note the ; it mean your if is end
    System.out.println("You can't visit in the park, " + name + ".");

4个

相反，你可以在循环中阅读年龄：

System.out.print("Hey, what's your name? ");
name = keyboard.next();
System.out.println();

do {

    System.out.print("Ok, " + name + ", how old are you? ");
    age = keyboard.nextInt();
    System.out.println();
    ....
}while(..);

---

希望这能让你了解你的问题

Answer 2

请试试这个：

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

        int value = 0;
        int age;

        System.out.print("Hey, what's your name? ");
        String name = keyboard.next();
        System.out.println();

        while(true) {
            System.out.print("Ok, " + name + ", how old are you? ");
            age = keyboard.nextInt();
            System.out.println();
            if (age <= 300) {
                break;
            }
            System.out.println("It's not correct..Try Again, " + name +
            ".");
        }

        if(age < 16) {
            System.out.println("You can't visit in the museum, " + name + ".");
        }
        if(age < 18){
            System.out.println("You can't visit in the park, " + name + ".");
        }
        if (age < 25){
            System.out.println("You can't visit if you have a car, " + name + ".");
        }
        if (age >= 25){
            System.out.println("You can do anything, " +
                name + ".");

        }
    }
}

Answer 3

1）应该使用以下条件：if (age >= 25 && age <= 300){而不是 if (age >= 25){

否则条件为true，即使age超过300并且您不想：

while(age > 300);

2）如果值不正确，还应允许用户输入新的输入

age = keyboard.nextInt();应该在循环中

3）你应该让循环完成。
在while语句中，可以指定需要用户进行新输入的条件：

while (age > 300)

这就给出了代码（未测试）：

  int age;
  do{
    age = keyboard.nextInt();

    if(age < 16){
        System.out.println("You can't visit in the museum, " + name + ".");
    }
    else if(age < 18){
         System.out.println("You can't visit in the park, " + name + ".");
    }
    else if (age < 25){
        System.out.println("You can't visit if you have a car, " + name + ".");
    }

    if (age >= 25 && age <= 300){
        System.out.println("You can do anything, " + 
            name + ".");                
    }
    else{
        System.out.println("It's not correct..Try Again, " + name +  ".");
    }
  }                 
  while (age > 300);