[Pattern] Collection bulk operations instead of mutation loops

[brunoborges]

Category

collections

Slug

collection-bulk-operations

Title

Collection bulk operations instead of mutation loops

Difficulty

beginner

Since JDK

8

Summary

Use removeIf(), replaceAll(), and List.sort() for direct collection transformations.

Old code label

Iterator mutation loop

Old code

for (Iterator<Order> it = orders.iterator(); it.hasNext();) {
    if (it.next().cancelled()) {
        it.remove();
    }
}

Modern code label

Java 8+

Modern code

orders.removeIf(Order::cancelled);

Explanation

Modern collection interfaces expose common mutations directly. These methods replace control-flow-heavy loops with operations that state the intended transformation.

Why the modern way wins

👁 Clear intent — The operation describes what changes, not how to iterate.
🐛 Safer mutation — Avoids manual iterator-removal rules.
⚡ Less code — Common transformations become a single expression.