How Can I Effectively Determine if a Java String Represents an Integer?

Determine if a String Represents an Integer in Java

Java does not provide a straightforward method to check if a string is an integer. However, there are various approaches to accomplish this:

Naive Method:

Iterate through the string and ensure that all characters are valid digits for the given radix. This is the most efficient method as it examines each character only once.

Library-Based Method:

Use Java's Scanner class to check if the string can be parsed as an integer of the specified radix. This method is more expensive than the naive approach but handles various error conditions.

Exception-Handling Method:

Use the parseInt method of the Integer class. If the parsing succeeds, the string represents an integer. However, this method throws exceptions for invalid inputs, which may not be desirable.

Here is an example implementation of the naive method:

public static boolean isInteger(String s) {
    return isInteger(s, 10);
}

public static boolean isInteger(String s, int radix) {
    if (s.isEmpty()) {
        return false;
    }
    for (int i = 0; i < s.length(); i++) {
        if (i == 0 && s.charAt(i) == '-') {
            if (s.length() == 1) {
                return false;
            } else {
                continue;
            }
        }
        if (Character.digit(s.charAt(i), radix) < 0) {
            return false;
        }
    }
    return true;
}

Ultimately, the best method to use depends on performance requirements and whether exception handling is preferred.

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