Explanation

What is NullPointerException? In Java, null means the reference is not pointing to any object. If you try to use a null reference, Java throws: java.lang.NullPointerException

Code Example

Explanation

Basic Null Check #white-Without Null Check String name = null; System.out.println(name.length());

Code Example

With Null Check
String name = null;
if (name != null) {
  System.out.println(name.length());
} else {
    System.out.println("Name is null");
}

Explanation

Using Ternary Operator

Code Example

String name = null;

int length = (name != null) ? name.length() : 0;

System.out.println(length);

Explanation

Using Objects Class (Java 7+) Java provides Objects utility class. Objects.requireNonNull() Throws custom error if null.

Code Example

import java.util.Objects;

String name = null;
Objects.requireNonNull(name, "Name cannot be null");
Output:
Exception: Name cannot be null

Explanation

Objects.isNull() and Objects.nonNull()

Code Example

import java.util.Objects;

String name = null;

if (Objects.isNull(name)) {
    System.out.println("Name is null");
}

Explanation

Using Optional (Java 8+) Optional helps avoid direct null handling.

Code Example

import java.util.Optional;

String name = null;

Optional<String> optionalName = Optional.ofNullable(name);

optionalName.orElse("Default Name");
//Default Name

Explanation

With ifPresent()

Code Example

Optional<String> optionalName = 
Optional.ofNullable("hackforge");

optionalName.ifPresent(n -> 
System.out.println(n));

Explanation

Using Java 14+ Objects.requireNonNullElse()

Code Example

import java.util.Objects;


String name = null;


String result = Objects.requireNonNullElse(name, "Default");

System.out.println(result);

Explanation

Code Example

1.Always validate method parameters

2.Use Optional for return types (not for fields)

3.Use constant-first string comparison

4.Avoid returning null — return empty list instead

Hackforge Academy

Explanation

Code Example

Explanation

Code Example

Explanation

Code Example

Explanation

Code Example

Explanation

Code Example

Explanation

Code Example

Explanation

Code Example

Explanation

Code Example

Explanation

Code Example

Want structured learning with real projects?