Java 8 brought some powerful new methods to Map that made working with associative arrays (maps) much cleaner, safer, and more expressive. 💡 Let’s go over the most useful ones:
✅ New Map Methods in Java 8
| Method | Purpose |
|---|---|
getOrDefault() | Returns value if present, or default value if key is missing |
putIfAbsent() | Puts a value only if the key is not already associated with one |
compute(), computeIfAbsent(), computeIfPresent() | Dynamically compute values |
merge() | Merges values in a map using a remapping function |
forEach() | Iterates over entries using a BiConsumer |
replace() | Replaces value for a key (optional conditional version) |
replaceAll() | Replaces all values using a BiFunction |
remove(key, value) | Removes entry only if key maps to that exact value |
🔍 Examples of Each
🔹 getOrDefault()
map.getOrDefault("apple", 0); // returns 0 if "apple" is not found
🔹 putIfAbsent()
map.putIfAbsent("apple", 10); // only puts if key not present
🔹 computeIfAbsent()
map.computeIfAbsent("banana", k -> 42); // adds banana=42 if not presentGreat for lazy loading or initializing maps.
🔹 computeIfPresent()
map.computeIfPresent("apple", (k, v) -> v + 1); // only updates if present
🔹 compute()
map.compute("apple", (k, v) -> (v == null) ? 1 : v + 1);
Use when you don’t care whether the key exists or not.
🔹 merge()
map.merge("apple", 1, Integer::sum); // adds or updates value by summingVery useful for counting frequency of items!
🔹 forEach()
map.forEach((key, value) -> System.out.println(key + ": " + value));
🔹 replace() and replaceAll()
map.replace("apple", 5); // replaces value
map.replaceAll((k, v) -> v * 2); // doubles all values
🔹 remove(key, value)
map.remove("apple", 10); // only removes if key maps to 10
🧠 Use Cases
- Building caches or counters with
computeIfAbsent/merge - Writing cleaner iteration logic with
forEach - Simplifying default value logic with
getOrDefault - Avoiding race conditions in concurrent use cases