Question

每当提示用户输入变量时，都不会检查第一个输入的变量，但之后会检查所有变量。

这是我的代码：

import java.util.*;

public class classOfValidation {

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

    System.out.println("This program checks the validity of variables");
    System.out.println("Please enter a variable (or press 'q' to quit)");
    theVariable = scan.nextLine();

    while (true) {
       theVariable = scan.nextLine();
            if ("q".equals(theVariable)) {
                System.out.println("Program quitted. Goodbye!");
                continue;
            }      
            if (theVariable.matches("^\\d+.*|.*\\s+.*")) {
               System.out.println("The variable is illegal");
               System.out.println("Please enter a variable (or press 'q' to quit)");
               continue;
            }     
            if (theVariable.matches("^[!@#$%^&*].*")) {
               System.out.println("The variable is legal, but has bad style");
               System.out.println("Please enter a variable (or press 'q' to quit)");
               continue;
            }
       break;
   }

    System.out.println("The variable is legal and has good style");
    scan.close();

    }

}

Answer 1

这是因为你有一行

theVariable = scan.nextLine();

在你的while循环之外

。删除该行，你应该是金色的。

Answer 2

在进行任何检查之前，您要将变量值设置为下一个扫描输入。

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

System.out.println("This program checks the validity of variables");
System.out.println("Please enter a variable (or press 'q' to quit)");

//Here the variable is the value of the first input.

theVariable = scan.nextLine();
 //The variable has not been checked but right after the "while (true)" you scan for the next value.

while (true) {
 //Here you replace the first value with the second and never check it.     

 theVariable = scan.nextLine();
 //move this to the end of your lool, so the variable gets replace with the next one AFTER the checking code has run on the first one.

        if ("q".equals(theVariable)) {
            System.out.println("Program quitted. Goodbye!");
       continue;
        }      
        if (theVariable.matches("^\\d+.*|.*\\s+.*")) {
       System.out.println("The variable is illegal");
       System.out.println("Please enter a variable (or press 'q' to quit)");
       continue;
        }     
        if (theVariable.matches("^[!@#$%^&*].*")) {
       System.out.println("The variable is legal, but has bad style");
       System.out.println("Please enter a variable (or press 'q' to quit)");
       continue;
 //Move it to here, scanning the next variable after the first is checked.
   theVariable = scan.nextLine();
        }
   break;
 }

 System.out.println("The variable is legal and has good style");
scan.close();

    }

 }

验证项目 - 程序不接受用户的第一个输入

2 个答案: