使用布尔值检测小写字母。结果总是正确的。

Question

我正在尝试创建一个代码来读取密码，如果密码包含小写字母，则布尔值应为 false 并继续执行其余代码。这是代码片段：

import java.util.Scanner;

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

    System.out.print("Enter a password that meets the following rules: \n\n");
    System.out.print("8 characteres long\n");
    System.out.print("Contains at least 1 lower letter\n");
    System.out.print("Contains at least 1 upper letter\n");
    System.out.print("Contains at least 1 numeric digit\n");
    System.out.print("Contains 1 special character from "
    + "the set: !@#$%^&*\n");
    System.out.print("Does not contain the word \"and\" "
    + "or the word \"end\"\n\n");
    String password = stdIn.nextLine();

    boolean hasLower;
    hasLower = true;
    for(int i = 0; (i<password.length()) && (!hasLower); i++){
          if(Character.isLowerCase(password.charAt(i))){
                hasLower = false;
        }
    }
    System.out.println(hasLower);
    } //end main
} // end class

Answer 1

你在for循环中的逻辑不正确。

由于您将 hasLower 变量初始化为真，for 循环中的条件永远不会为真，因此 for 循环永远不会运行:

(i<password.length()) && (!hasLower) 
// !hasLower will not be true since the variable is initialised to true, whereas it should be initialised to false.

因此，要修复代码，请将 hasLower 变量初始化为 false，然后在找到小写字符时退出循环。

hasLower = false;
for(int i = 0; i < password.length(); i++){
      if(Character.isLowerCase(password.charAt(i))){
            hasLower = true;
            break; // Exits the last-entered loop.
    }
}

Answer 2

按照您的逻辑，它将跳过 for 循环。请将第二个 && 运算符更改为 (hasLower)。注意：不需要这些括号。

你可能有如下内容

for (int i = 0; i < password.length() && hasLower; i++) {
        if (Character.isLowerCase(password.charAt(i))) {
            hasLower = false;
        }
    }

使用布尔值检测小写字母。结果总是正确的。

Using boolean to detect lower cases. Outcome always true.

java

boolean