The Stacks
UNIT 4 · 30–40% OF THE EXAM · 17 TOPICS

Data Collections

The biggest unit and the source of three of the four FRQs. Arrays, ArrayLists, 2D arrays, then searching, sorting, and recursion. If Unit 4 is solid, a 5 is realistic.

What the College Board expects you to walk away understanding

  • Data sets are stored in arrays, ArrayLists, and 2D arrays, each with its own creation, access, and traversal rules.
  • Standard algorithms — sum, max, count, filter, search, sort — are applied across all three structures.
  • Text files are read with Scanner and File, and wrapper classes let numbers live in ArrayLists.
  • Recursion is traced (not written), including recursive binary search and merge sort.

Topics in this Unit

Night-before review

Every key term and exam tip from this unit on one printable page.

□Unit 4 cheat sheetprint