Java作业求助：实现StringVerification接口及特殊字符检索

Hey there! Let's tackle your programming assignment issues one by one. First, we'll fix the broken EmailVerification class, then build the PhoneVerification class exactly as you need it—no extra imports required.

Your current EmailVerification has a few key issues:

• Syntax error in char at = @ ; (you need quotes around the @ character)
• It returns true as soon as it finds an @, without checking for the .
• The dot and atSymbol flags aren't reset between calls to verifyInput (so if you call the method multiple times, old values will stick around)
• The constructor's String at and String period variables are unused

Here's the corrected version, with explanations in comments:

public class EmailVerification implements StringVerification {
    // No need to keep these as instance variables—we can reset them per method call
    @Override
    public boolean verifyInput(String input) {
        // Handle null input first to avoid crashes
        if (input == null) {
            return false;
        }
        
        boolean hasAt = false;
        boolean hasDot = false;
        
        for (int i = 0; i < input.length(); i++) {
            char c = input.charAt(i);
            if (c == '@') {
                hasAt = true;
            } else if (c == '.') {
                hasDot = true;
            }
            // Optional: Early exit if both are found to save processing
            if (hasAt && hasDot) {
                break;
            }
        }
        
        // Return true only if both symbols exist
        return hasAt && hasDot;
    }
}

A few notes here:

• We declare hasAt and hasDot inside the method so they reset every time verifyInput is called
• We added a null check to prevent NullPointerException if someone passes null
• We can optionally break out of the loop early once both symbols are found (not required, but makes the code a bit more efficient)

You mentioned wanting to avoid imports—great news: Character.isDigit() is part of the core java.lang package, which is automatically imported into every Java class, so you don't need any extra import statements. Here's how to implement the class to check for 10-digit pure numbers:

public class PhoneVerification implements StringVerification {
    @Override
    public boolean verifyInput(String input) {
        // First check: input can't be null, and must be exactly 10 characters long
        if (input == null || input.length() != 10) {
            return false;
        }
        
        // Check each character to ensure it's a digit
        for (int i = 0; i < input.length(); i++) {
            char c = input.charAt(i);
            // Character.isDigit() checks if the character is a 0-9 digit
            if (!Character.isDigit(c)) {
                return false;
            }
        }
        
        // If we made it here, all checks passed
        return true;
    }
}

This code:

1. Immediately rejects null input or input that isn't 10 characters long
2. Iterates through each character, returning false as soon as a non-digit is found
3. Returns true only if all characters are digits and the length is correct

That should cover all the requirements of your assignment!

内容的提问来源于stack exchange，提问作者Jose Huertas