0

我的程序输出有问题。我开发了“GetInput”类作为构造函数，在询问各种输入问题时可以重用它。提出的每个问题都需要等于或大于最小值/小于传递给类/构造函数的最大值。我遇到的问题是，当 while 循环运行时，它要求输入四次，然后才最终返回正确的值。

我添加了我在它们显示时计算出来的标志。第一次添加输入后的第一个显示。然后是第二次，然后是第四次。第四次它还显示我希望它在一次迭代中达到的标志“结束”。为什么在最终正确返回值之前循环了四次？

提前非常感谢。这只是我学习 Java 的第二天，这让我发疯了。

import java.util.Scanner; //Import the scanner class

public class main {
public static void main(String[] args) {

    //Set variables to hold the entry cost for each category
    int costAccChild = 2;
    int costUnaccChild = 5;
    int costAdult = 10;
    int costSenior = 8;

    int test = GetInput(0, 1, "Enter a group? (Yes=1/No=0)");
    System.out.println(test);
    System.out.println("the end");

}

 static int GetInput(int min, int max, String request){     
    boolean inputValid = false; //Sets default value to variable for while loop
    int userInput = 0; //Sets default variable for input return

    while (inputValid == false) { //Loops until receives correct input
        System.out.println(request); //Prints question asking for input
        Scanner inputFromUser = new Scanner(System.in); //Ask user for input
        System.out.print("First time"); //FLAG DISPLAYS AFTER FIRST SCANNER

        if (inputFromUser.hasNextInt() == true){ //Check if input has an integer

            System.out.print("Second Time"); //FLAG SHOWS AFTER SECOND SCANNER

            if (inputFromUser.nextInt() >= min && inputFromUser.nextInt() <= max ){ //Check if input is valid
                userInput = inputFromUser.nextInt();
                inputValid= true;

                System.out.print("Fourth time"); //FLAG WORKS FORTH TIME

            }else{ //Input is not correct integer, give error message
                System.out.println("Input is not valid");           
                }   

        }else{ //Input is not an integer at all, give error message
            System.out.println("Input is not valid");
        }
    }
    return userInput; //Returns valid input
    }
}
4

2 回答 2

2

从手册页http://docs.oracle.com/javase/6/docs/api/java/util/Scanner.html#hasNextLong()：

hasNext 和 next 方法都可能阻塞等待进一步的输入

它没有循环 4 次，但每当你说inputFromUser.hasNextInt()或inputFromUser.nextInt()扫描仪实际上阻止等待你输入一个值。

所以这显然是一个你必须修复的错误

于 2013-03-19T11:14:05.990 回答
0

您应该将输入存储在某个变量中，然后在 if 条件下比较它们。

这不会阻止输入以进行进一步输入。

尝试这个：

public static void main(String[] args) {

    //Set variables to hold the entry cost for each category
    int costAccChild = 2;
    int costUnaccChild = 5;
    int costAdult = 10;
    int costSenior = 8;

    int test = GetInput(0, 1, "Enter a group? (Yes=1/No=0)");
    System.out.println("Return Result: " + test);
    System.out.println("The end");

}

static int GetInput(int min, int max, String request) {
        boolean inputValid = false; //Sets default value to variable for while loop
        int userInputMin = 0, userInputMax=0; //Sets default variable for input return

        while (inputValid == false) { //Loops until receives correct input
            System.out.println(request); //Prints question asking for input
            Scanner inputFromUser = new Scanner(System.in); //Ask user for input
            System.out.print("First time: "); //FLAG DISPLAYS AFTER FIRST SCANNER

            if (inputFromUser.hasNextInt() == true) { //Check if input has an integer
                userInputMin = inputFromUser.nextInt();
                System.out.print("Second Time: "); //FLAG SHOWS AFTER SECOND SCANNER
                if (inputFromUser.hasNextInt() == true) { //Check if input has an integer
                    userInputMax = inputFromUser.nextInt();
                    if (userInputMin >= min && userInputMax <= max) { //Check if input is valid

                        inputValid = true;

                        System.out.println("Third time"); //FLAG WORKS Third Time

                    } else { //Input is not correct integer, give error message
                        System.out.println("Input is not valid");
                    }
                }    
            } else { //Input is not an integer at all, give error message
                System.out.println("Input is not valid");
            }
        }
        return userInputMin; //Returns valid input
    }
于 2013-03-19T11:24:32.380 回答