in-memory-repository-sorting-sample

Extends in-memory-repository-sample with sorting support.

What It Demonstrates

Adds a Comparator<Owner> parameter to the repository interface.

The caller controls the sort order — the repository applies it before returning results.

Passing null skips sorting and returns records in insertion order.

Structure

All code is in a single file: InMemoryRepositorySortingApp.java

InMemoryRepositorySortingApp.java
│
├── Owner                          # Entity — record with id and name
├── OwnerRepository                # Repository interface with Comparator<Owner> parameter
├── FakeOwnerRepository            # In-memory implementation using LinkedHashMap
└── InMemoryRepositorySortingApp   # Entry point + demo()

Key Points

Comparator as a parameter. The repository interface accepts a Comparator<Owner> — the caller decides the order, the repository just applies it.

Null means no sorting. Passing null returns records in their natural insertion order — no special case needed in the caller.

Original data is never mutated. Sorting is applied on a stream — the underlying LinkedHashMap stays unchanged.

Console Output

Owner[id=1, name=jack1]
Owner[id=2, name=jack2]
Owner[id=3, name=jack3]
Owner[id=4, name=jack4]
Owner[id=5, name=jack5]

Owner[id=5, name=jack5]
Owner[id=4, name=jack4]
Owner[id=3, name=jack3]
Owner[id=2, name=jack2]
Owner[id=1, name=jack1]

Owner[id=1, name=jack1]
Owner[id=2, name=jack2]
Owner[id=3, name=jack3]
Owner[id=4, name=jack4]
Owner[id=5, name=jack5]

First block — sorted by id ascending. Second — by id descending. Third — no sorting, insertion order.

Run

./mvnw spring-boot:run

See also

• Previous: in-memory-repository-sample
• Next: pagination-pageable-sample