How is NullPointerException in Java 14 different from its predecessor?

The JVM throws a NullPointerException at the point in a program where code tries to dereference a null reference. With Java SE 14, the NullPointerException offers helpful information about the premature termination of a program. Java SE 14 onwards, the JVM describes the variable (in terms of source code) with a null-detail message in the NullPointerException. It greatly improves program understanding by more clearly associating a dynamic exception with static program code.

We can see the difference with an example.

import java.util.ArrayList;
import java.util.List;

class Price {
    double basePrice;
    double tax;

    public Price() {
    }

    public Price(double basePrice) {
        this.basePrice = basePrice;
    }

    public Price(double basePrice, double tax) {
        this.basePrice = basePrice;
        this.tax = tax;
    }
    // ...
}

class Product {
    String name;
    Price price;

    public Product() {
    }

    public Product(String name, Price price) {
        this.name = name;
        this.price = price;
    }
    // ...
}

class CartEntry {
    Product product;
    int quantity;

    public CartEntry() {
    }

    public CartEntry(Product product, int quantity) {
        this.product = product;
        this.quantity = quantity;
    }

    // ...
}

class Cart {
    String id;
    List<CartEntry> cartEntries;

    public Cart() {
        cartEntries = new ArrayList<>();
    }

    public Cart(String id) {
        this();
        this.id = id;
    }

    void addToCart(CartEntry entry) {
        cartEntries.add(entry);
    }
    // ...
}

public class Main {
    public static void main(String[] args) {
        Cart cart = new Cart("XYZ123");
        cart.addToCart(new CartEntry());
        System.out.println(cart.cartEntries.get(0).product.price.basePrice);
    }
}

Output before Java SE 14:

Exception in thread "main" java.lang.NullPointerException
    at Main.main(Main.java:74)

This message leaves the programmer clueless about the source of the NullPointerException.

The output with Java SE 14 onwards:

Exception in thread "main" java.lang.NullPointerException: Cannot read field "price" because "java.util.List.get(int).product" is null
    at Main.main(Main.java:74)

The NullPointerException in Java SE 14 also tells us which reference is null.

A great improvement!