How to Simplify Key Existence Checking in a Java Map?

Is there a utility or Map implementation in Java that simplifies the key existence checking and throws an exception with a custom message if the key is absent?

if (!map_instance.containsKey(key))
    throw new RuntimeException("Specified key doesn't exist in map");
else
   return map_instance.get(key);

When working with Maps in Java, verifying the existence of a key can become verbose and repetitive. However, you can create a custom utility method or modify the existing Map implementations to achieve this in a more streamlined manner. Your requirement is indeed reasonable and can enhance code readability and reduce boilerplate code.

import java.util.Map;

public class CustomMap<K, V> {
    private final Map<K, V> map;

    public CustomMap(Map<K, V> map) {
        this.map = map;
    }

    public V getOrThrow(K key, String message) {
        if (!map.containsKey(key)) {
            throw new RuntimeException(message);
        }
        return map.get(key);
    }
}

Causes

• Using standard Map methods like `containsKey()` and `get()` can lead to multiple lines of code for simple existence checks.
• Lack of custom utility methods in default Java Map implementations to handle key-existence checks with exception messages.

Solutions

• Create a custom wrapper around the existing Map that includes a method to retrieve a value or throw an exception with a custom message if the key does not exist.
• Use a utility class that leverages default Java Map methods but encapsulates the logic to throw exceptions with specified messages.

Mistake: Not handling NullPointerExceptions that may arise if the key is null when passing it to `containsKey()` or `get()`.

Solution: Ensure to check if the key is null before making calls on the Map.

Mistake: Throwing generic exceptions instead of custom ones, which are harder to debug.

Solution: Consider creating custom exception classes for better error identification.