How Can I Check if a Java String Represents an Integer?

Determining if a String Represents an Integer in Java

In Java, there is often a need to determine if a given element in an array of strings represents an integer value. This can be encountered when parsing complex expressions, separating numerical data from other values, or verifying user input.

One way to approach this is by iterating through each character of the string and examining if it is a valid digit based on the desired radix. Here's a sample implementation:

public static boolean isInteger(String s) {
    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), 10) < 0) {
            return false;
        }
    }
    return true;
}

Alternatively, one can leverage Java's built-in features:

public static boolean isInteger(String s, int radix) {
    Scanner sc = new Scanner(s.trim());
    if (!sc.hasNextInt(radix)) {
        return false;
    }
    sc.nextInt(radix);
    return !sc.hasNext();
}

Lastly, a less recommended approach is to rely on exception handling:

public static boolean isInteger(String s) {
    try {
        Integer.parseInt(s);
    } catch (NumberFormatException | NullPointerException e) {
        return false;
    }
    return true;
}

These techniques provide flexible ways to determine if a string represents an integer, ensuring the integrity of data processing and validation in various Java applications.

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