我目前正在为我的Java课程开展最后的项目，我需要一些帮助！首先，我将向您展示说明，我的代码，然后是我的问题。
说明
检查密码，看它是否只包含字母和数字。为此，您需要遍历字符串中的所有字符。如果此表达式为真，则字符c是一个数字字母：
（'a'＆lt; = c＆amp;＆amp; c＆lt; ='z'）|| （'A'＆lt; = c＆amp;＆amp; c＆lt; ='Z'）|| （'0'＆lt; = c＆amp;＆amp; c＆lt; ='9'）
如果这不是真的，请从循环中断并显示消息“密码必须只包含字母和数字” 5.如果在程序结束时仍然有效，则显示消息“密码接受！”
我的代码
import java.util.Scanner;
public class PasswordVerification {
public static void main(String[] args) {
// Creates a scanner
Scanner sc = new Scanner(System.in);
boolean valid = false;
String password;
// Asks user to enter password
System.out.print("Please enter password and then hit enter:");
password = sc.nextLine();
// Checks to see if password is at least 8 characters.
if (password.length()<8)
{
valid = false;
System.out.println("Password must have at least 8 characters");
}
// Checks each character to see if it is acceptable.
for (int i = 0; i < password.length(); i++){
char c = password.charAt(i);
if ( ('a' <= c && c <= 'z') // Checks if it is a lower case letter
|| ('A' <= c && c <= 'Z') //Checks if it is an upper case letter
|| ('0' <= c && c <= '9') //Checks to see if it is a digit
)
{
valid = true;
}
else
{
// tells the user that only letters & digits are allowed
System.out.println("Only letter & digits are acceptable.");
valid = false;
break;
}
}
// if the password is valid, tell the user it's accepted
System.out.println("Password Accepted");
}
}
所以我到目前为止有说明和我的代码。我很接近完成我只是遇到第四部分的问题。所以预期的输出应该是：
Please enter a password: abc
Password much have at least 8 characters
Please enter a password: abcd1234$
Password must only contain letter and digits
Please enter a password: ####
Password must have at least 8 characters
Password must only contain letters and digits
Please enter a password: abcd1234
Password accepted!
当我输入abc时，这就是我得到的：
Please enter password and then hit enter:abc
Password must have at least 8 characters
Password Accepted
当我这样做时，程序结束了！有人可以帮助我吗？提前致谢。 =）另外，这是一个Java Programming I类。
答案 0 :(得分：2)
正如@cralfaro所说，如果密码无效，你必须重复这个过程：
import java.util.Scanner;
public class PasswordVerification {
public static void main(String[] args) {
// Creates a scanner
Scanner sc = new Scanner(System.in);
boolean valid = false;
String password;
do { // start a loop
// Asks user to enter password
System.out.print("Please enter password and then hit enter:");
password = sc.nextLine();
// Checks to see if password is at least 8 characters.
if (password.length()<8)
{
valid = false;
System.out.println("Password must have at least 8 characters");
continue; // skip to next iteration
}
// Checks each character to see if it is acceptable.
for (int i = 0; i < password.length(); i++){
char c = password.charAt(i);
if ( ('a' <= c && c <= 'z') // Checks if it is a lower case letter
|| ('A' <= c && c <= 'Z') //Checks if it is an upper case letter
|| ('0' <= c && c <= '9') //Checks to see if it is a digit
)
{
valid = true;
}
else
{
// tells the user that only letters & digits are allowed
System.out.println("Only letter & digits are acceptable.");
valid = false;
break;
}
}
} while(!valid); // verify if the password is valid, if not repeat the process
// if the password is valid, tell the user it's accepted
System.out.println("Password Accepted");
}
}
通过这种方式，如果密码无效，程序将继续询问用户输入。
修改 感谢GC_的评论，问题是我错过了第一次检查中的继续声明。
答案 1 :(得分：0)
你的问题是这部分代码：
onUserSelectedOption = (option, index) => {
this.setState({
userSelectedIndex: index
});
if (option.correct === 1) {
//do something
}else {
//do something
}
}
render(){
const result = this.state.data.map((data) =>{
const xx = data.option.map((option, index)=>{
return (
<TouchableHighlight onPress={() => this.onUserSelectedOption(option, index)}>
<Text key={option.option_id} style={{backgroundColor: index === this.state.userSelectedIndex ? 'red' : 'transparent' }}>{option.options}</Text>
</TouchableHighlight>
)
})
return(
<View>
<Text style={styles.titles}>{data.title}</Text>
{xx}
</View>
)
})
return(
<ScrollView>
{result}
</ScrollView>
);
}
此处您将if ( ('a' <= c && c <= 'z') // Checks if it is a lower case letter
|| ('A' <= c && c <= 'Z') //Checks if it is an upper case letter
|| ('0' <= c && c <= '9') //Checks to see if it is a digit
) { valid = true; }
重置为valid，即使长度小于true的第一次检查已失败。
因此8将失败abc并打印3.，这很好。然后它将通过Password must have at least 8 characters，重置有效至4.并打印true。
所以你想要用{/ 1>替换Password Accepted部分
if (...) { valid = true; } else { ... } 修改：
另外，您最初应设置if (!( // if the character is none of the options below, print error
('a' <= c && c <= 'z') // Checks if it is a lower case letter
|| ('A' <= c && c <= 'Z') //Checks if it is an upper case letter
|| ('0' <= c && c <= '9') //Checks to see if it is a digit
)) {
// tells the user that only letters & digits are allowed
System.out.println("Only letter & digits are acceptable.");
valid = false;
break;
}
而不是boolean valid = true;，因为只有在条件失败时才将其设置为false。
然后在代码的末尾添加一个条件，检查最后一个输出行周围的false，如
valid答案 2 :(得分：0)
有点乱，但试试这个：
pPoolSizes答案 3 :(得分：-1)
在打印密码被接受之前，添加一项检查以查看密码是否仍然有效。
if(valid==true) {
System.out.println("Password Accepted");
}
编辑：您也可以添加此内容。
else {
System.out.println("Password Denied");
}