String.valueof() vs. Object.toString()

java

null-safety

logging

best-practices

byNikita Barsukov·Mar 7, 2025

Opt for String.valueOf() when in need of a null-safe conversion to string since it transforms null into "null". However, use Object.toString() when you're assured the object is non-null for invoking its specific toString().

Object obj = null;
String safe = String.valueOf(obj);  // "null", null be chillin' in a string
String risky = obj.toString();      // Exception, NPE party time!

In nutshell, use String.valueOf() as a defense against NullPointerException, but keep obj.toString() for guaranteed non-null objects awaiting their textual makeover.

Dealing with primitives and wrong casting

When it comes to primitives, .toString() is a no-go zone. String.valueOf() gives a helping hand here with a host of overloaded methods for primitive conversion:

int num = 5;
String fromInt = String.valueOf(num); // "5", primitives can't even toString without adult supervision

Alternatively, using .toString() on an off-type object may lead to a dreaded ClassCastException, but since String.valueOf() accepts any Object, it handles any rogue elements gracefully:

Object obj = 5; // Autoboxing like a champ
String fromObject = String.valueOf(obj); // Easy peasy lemon squeezy
String riskyCast = ((String) obj).toString(); // YOLO, Throws ClassCastException

Code design: less defense, more offense

A strong offense is often the best defense. Instead of huddling behind the safety of String.valueOf(), tackle the root cause of null values head-on:

public String getUsername(User user) {
    return user != null ? user.getUsername() : "User is a ninja"; // null-user, more stealthy than ninja
}

Facing down null values at the source is much more robust than defensive coding employing null-safe methods.

Inside the box of String.valueOf()

Peering into String.valueOf(Object), it calls upon the toString() method of any non-null object, else it gives "null" a safe haven:

public static String valueOf(Object obj) {
    return (obj == null) ? "null" : obj.toString(); // Safety first. Always.
}

Understanding this can elucidate why String.valueOf() is your go-to for robust null handling.

How to choose your fighter

Load up String.valueOf() when dealing with:

Potentially null inputs
Log statements (let's not let logging be the villain of the piece)
Primitives or generic objects

Go to war with obj.toString() when:

The object is a sure thing (aka non-null)
A particular implementation of toString() is your weapon of choice

Boost your Java code Quality

Weaving knowledge of when to use String.valueOf() vs. Object.toString() benefits not just your personal growth as a developer, but also your code quality and robustness. Honour the intention of each method:

Custom toString() versions for fancy and meaningful strings
Deploy String.valueOf() as a lifesaver in times of unpredictable storms of null objects scaling your castle

With these insights, you are on your journey towards becoming a Java maestro.

What Would Java Do (WWJD)?

Java is more than choosing between methods - it's about cherishing good practices:

Override toString() for a more human-readable and debug-friendly object description.
Save String.valueOf() for logging and transient operations where null is a uninvited guest
Remember context is king. Analyze the SITUATION before choosing your string conversion method