How to check if my string is equal to null?

Understanding the null terrain

In a string's life, it can encounter varying null scenarios. Armed with the right knowledge, you traverse them courageously:

Speaking null and empty

Acknowledging that null and "" (empty) are distinct states for strings is paramount:

• null is as if the string just disappeared—vanished into thin air.
• An empty string ("") exists but has no characters. It's similar to an open stage but sadly, no performers.

Navigating equals() method

The world's cruel, and using .equals() on a null reference will get you nothing but NullPointerException. To ward this off, here's a secret spell:

if ("expectedString".equals(myString)) {
    // Occlumency level: 100
}


Entering Apache Territory

Why work extra when Apache's got you covered? StringUtils.isNotEmpty(myString) from Apache commons-lang ensures a thorough check including whitespace patrol:

if (StringUtils.isNotEmpty(myString)) {
    // Even white spaces can't slide under the radar
}


About those "null gotchas"

Life's a bumpy ride and x.field or x.method() will betray you with a NullPointerException if x is null. Always equip yourself with nullity checks before diving into methods or accessing fields.

Mastering null-check techniques

The basics are easy to grasp, but mastering null-checks requires getting your hands dirty:

Literals first, equals() second

To shield against NullPointerExceptions, deploy the reversed .equals()—bait with a literal or a constant first:

if ("Golden Snitch".equals(myString)) {
    // Catch the snitch, win the game, easy-peasy
}


A lifesaver when myString could potentially be null.

Auto-unboxing ambush

When meddling with boxed primitives (like Integer), remember that null refuses to be auto-unboxed:

Integer quidditchPoints = null;
int result = quidditchPoints; // Ouch, it's a bludger! NullPointerException


Book of Null-Safe Libraries

Solve the null mystery with libraries like Guava or Apache Commons that offer null-safe charms and StringUtils potions to handle strings effortlessly.

Null lurking in collections

Beware of the streams and collections that may return null. For instance, Map.get() is a trickster that can return null if a key is missing. Therefore, always consider Map.containsKey() or setting up a default value with getOrDefault().