如果布爾變量為true，如何獲取要打印的程序？

Question

我知道這似乎是一個非常簡單的問題，但請記住，我是Java的新手。 附帶的是我的源代碼，最后寫了if語句，如果變量“ valid”為true，則打印出“ Password is valid”。 該代碼可以正常運行，直到達到這一點為止，此時退出程序而不是打印“ password有效”。 我查看了堆棧溢出中的多個線程，以了解如何解決該問題，並且大多數線程建議該代碼可以正常工作。 任何意見，將不勝感激。 謝謝

import java.util.Scanner;

public class PasswordValidator {

public static void main(String[] args) {
    //declare name and pass and insert scanner
    Scanner sc = new Scanner(System.in);
    String name = "name";
    String pass = "pass";

    // tell user to type name and password and store  as variables
    System.out.print("Enter user name: ");
    name = sc.nextLine();
    check(name);  // check if name is equal to -1
    System.out.print("Enter password: ");
    pass = sc.nextLine();
    validate(name,pass); // call method 
}

static boolean validate(String userName, String password) {
    //declare necessary variables
    String upperCase = ".*[A-Z].*";
    String lowerCase = ".*[a-z].*";
    String number = ".*[0-9].*";
    String special = ".*[^A-Za-z0-9 ].*";
    boolean valid = true;

    if (password.matches("-1")) { // if input for password is -1 exit program
        System.exit(0);
    }
    if (password.matches(upperCase)) {  // check to see if input has one upper case letter  
        valid = true;
    }
        else  
            System.out.println("Password should contain at least one upper-case alphabet.");
            valid = false;
    if(password.matches(lowerCase)) {  // check to see if input has one lower case letter
        valid = true;
    }
        else 
            System.out.println("Password should contain at least one lower-case alphabet.");
            valid = false;  
    if (password.matches(number)) { // check to see if input has one number
        valid = true;
    }
        else
            System.out.println("Password should contain at least one number.");
            valid = false;      
    if(password.matches(special)) { // check to see if input has a special char.
        valid = true;
    }
        else
            System.out.println("Password should contain at least one special character.");
            valid = false;      
    if(password.length()>=7 && password.length() <= 10) { // make sure the password input = 7-10 char.
        valid = true;
    }
        else 
            System.out.println("Password should be within 7 to 10 characters in length.");  
            valid = false;  

    if (password.matches(".*\\s.*")) { // check to see if input has white spaces
        System.out.println("Password should not contain whitespace.");
        valid = false;
    }

    if(password.matches(userName))  { // give error if user name and password are the same
        System.out.println("Password should not contain or be the same as username.");
        valid = false;
    }
    // this is where I try to print if password is valid. for some reason my program just exits without printing :(
    if(valid==true) {
        System.out.print("Password is valid");
    }

    return valid;

}

// method used to check if user name is -1, and close program if so
static boolean check(String userName) {
    if (userName.matches("-1")){
            System.exit(0);
    }
    return true;

}
}

Answer 1

這里的問題是括號。 您在else中打印一些語句，然后不管條件為true還是false，都將有效標志設置為false。 另外，最后關閉掃描儀。 另外，您無需檢查是否valid == true，只需將其置於if條件即可。 您的代碼看起來像

package com.digit.main;

import java.util.Scanner;

public class PasswordValidator {

public static void main(String[] args) {
    // declare name and pass and insert scanner
    Scanner sc = new Scanner(System.in);
    String name = "name";
    String pass = "pass";

    // tell user to type name and password and store as variables
    System.out.print("Enter user name: ");
    name = sc.nextLine();
    check(name); // check if name is equal to -1
    System.out.print("Enter password: ");
    pass = sc.nextLine();
    validate(name, pass); // call method
    sc.close();
}

static boolean validate(String userName, String password) {
    // declare necessary variables
    String upperCase = ".*[A-Z].*";
    String lowerCase = ".*[a-z].*";
    String number = ".*[0-9].*";
    String special = ".*[^A-Za-z0-9 ].*";
    boolean valid = true;

    if (password.matches("-1")) { // if input for password is -1 exit program
        System.exit(0);
    }
    if (password.matches(upperCase)) { // check to see if input has one upper case letter
        valid = true;
    } else {
        System.out.println("Password should contain at least one upper-case alphabet.");
        valid = false;
    }
    if (password.matches(lowerCase)) { // check to see if input has one lower case letter
        valid = true;
    } else {
        System.out.println("Password should contain at least one lower-case alphabet.");
        valid = false;
    }
    if (password.matches(number)) { // check to see if input has one number
        valid = true;
    } else {
        System.out.println("Password should contain at least one number.");
        valid = false;
    }
    if (password.matches(special)) { // check to see if input has a special char.
        valid = true;
    } else {
        System.out.println("Password should contain at least one special character.");
        valid = false;
    }
    if (password.length() >= 7 && password.length() <= 10) { // make sure the password input = 7-10 char.
        valid = true;
    } else {
        System.out.println("Password should be within 7 to 10 characters in length.");
        valid = false;
    }

    if (password.matches(".*\\s.*")) { // check to see if input has white spaces
        System.out.println("Password should not contain whitespace.");
        valid = false;
    }

    if (password.matches(userName)) { // give error if user name and password are the same
        System.out.println("Password should not contain or be the same as username.");
        valid = false;
    }
    // this is where I try to print if password is valid. for some reason my program
    // just exits without printing :(
    if (valid) {
        System.out.print("Password is valid");
    }

    return valid;

}

// method used to check if user name is -1, and close program if so
static boolean check(String userName) {
    if (userName.matches("-1")) {
        System.exit(0);
    }
    return true;

}

}

Answer 2

您的else子句不包含花括號，因此您多次將valid盲目地設置為false 。 此外，一旦測試失敗，您也不想將valid設置回true 。 同時解決這兩個問題，您應該會發現，

static boolean validate(String userName, String password) {
    // declare necessary variables
    String upperCase = ".*[A-Z].*";
    String lowerCase = ".*[a-z].*";
    String number = ".*[0-9].*";
    String special = ".*[^A-Za-z0-9 ].*";
    boolean valid = true;

    if (password.equals("-1")) {
        System.exit(0);
    }
    if (!password.matches(upperCase)) { // check to see if input has one upper case letter
        System.out.println("Password should contain at least one upper-case alphabet.");
        valid = false;
    }
    if (!password.matches(lowerCase)) { // check to see if input has one lower case letter
        System.out.println("Password should contain at least one lower-case alphabet.");
        valid = false;
    }
    if (!password.matches(number)) { // check to see if input has one number
        System.out.println("Password should contain at least one number.");
        valid = false;
    }
    if (!password.matches(special)) { // check to see if input has a special char.
        System.out.println("Password should contain at least one special character.");
        valid = false;
    }
    if (password.length() < 7 || password.length() > 10) { // make sure the password input = 7-10 char.
        System.out.println("Password should be within 7 to 10 characters in length.");
        valid = false;
    }
    if (password.matches(".*\\s.*")) { // check to see if input has white spaces
        System.out.println("Password should not contain whitespace.");
        valid = false;
    }
    if (password.matches(userName)) { // give error if user name and password are the same
        System.out.println("Password should not contain or be the same as username.");
        valid = false;
    }
    if (valid) {
        System.out.println("Password is valid");
    }

    return valid;
}

Answer 3

您應該將所有else部分放在方括號中，

例如：

而不是使用這個

else 
    System.out.println("Password should be within 7 to 10 characters in length.");  
    valid = false;  

請這樣使用

else
{
  System.out.println("Password should be within 7 to 10 characters in length.");
  valid = false;
}

您應該對所有else部分執行此操作，並且它應該可以工作。

如果使用不帶括號的else，則僅else后面的第一行將位於else 。 那就是您在這里所做的錯誤。 此外，如果您仔細了解了代碼的執行方式，則可以通過始終刪除不必要的false和true分配來改進代碼