IpValidator.java

import java.util.Arrays;

public class IpValidator {

    /**
     * Validates an IP address of the form w.x.y.z:port
     * - w, x, y, z must each be in range [0, 255] (one byte)
     * - port must be in range [1, 65535] inclusive
     */
    public static boolean isValidIpAddress(String input) {
        if (input == null || input.isEmpty()) {
            return false;
        }

        int port;
        if (input.indexOf(":") != -1) {
            try {
                port = Integer.parseInt(input.split(":", -1)[1]);
            } catch(NumberFormatException e) {
                return false;
            }
    
            if (port < 1 || port > 65535) {
                return false;
            }
        }

        String[] parts = input.split(":")[0].split("\\.");

        if (parts.length != 4) {
            return false;
        }

        Integer[] intParts;
        try {
            intParts = Arrays.stream(parts).map(Integer::valueOf).toArray(Integer[]::new);
        } catch(NumberFormatException e) {
            return false;
        }

        for (int number : intParts) {
            if (number < 0 || number > 255) {
                return false;
            }
        }
        
        return true;
    }

    public static void main(String[] args) {
        // Test cases
        String[] valid = {
            "192.168.1.1:8080",
            "0.0.0.0:1",
            "255.255.255.255:65535",
            "10.0.0.1:443",
        };
        String[] invalid = {
            "256.0.0.1:80",       // octet out of range
            "192.168.1.1:0",      // port 0 not allowed
            "192.168.1.1:65536",  // port too high
            "192.168.1:80",       // only 3 octets
            "192.168.1.1.1:80",   // 5 octets
            "192.168.1.abc:80",   // non-numeric octet
            "192.168.1.1:",       // empty port
            ":80",                // missing IP
            "",                   // empty string
        };
        String[] validNoPort = {
            "192.168.1.1",        // valid IP, no port
            "0.0.0.0",
            "255.255.255.255",
        };

        System.out.println("=== Should be TRUE ===");
        for (String s : valid) {
            boolean result = isValidIpAddress(s);
            System.out.printf("  %-30s -> %s%n", s, result ? "PASS" : "FAIL (expected true)");
        }

        System.out.println("=== Should be FALSE ===");
        for (String s : invalid) {
            boolean result = isValidIpAddress(s);
            System.out.printf("  %-30s -> %s%n", s, result ? "FAIL (expected false)" : "PASS");
        }

        System.out.println("=== Should be TRUE (no port) ===");
        for (String s : validNoPort) {
            boolean result = isValidIpAddress(s);
            System.out.printf("  %-30s -> %s%n", s, result ? "PASS" : "FAIL (expected true)");
        }
    }
}