ArrayList: every key term you need

ArrayList

Resizable array; grows/shrinks dynamically. ArrayList<Type> list = new ArrayList<>();. Type: Integer, String, custom classes.

ArrayList Methods

add(object): append. add(index, object): insert. remove(index): delete. get(index): access. size(): count. clear(): empty list.

ArrayList Type Parameter

<String> indicates ArrayList holds Strings. ArrayList<int> invalid (must use Integer). Generic type ensures type safety.

ArrayList Indexing

get(index) returns element; set(index, object) replaces. Index 0 to size()-1. Index out of range throws exception.

ArrayList vs Array

ArrayList: dynamic size, objects only, slower. Array: fixed size, primitives OK, faster. Choose based on needs.

Autoboxing/Unboxing

Automatic conversion: primitive ↔ wrapper class. int → Integer, double → Double. Enables primitives in generics.

ArrayList Iteration

For loop: for(int i=0; i<list.size(); i++) list.get(i). Enhanced for: for(String s : list). Iterator: while(it.hasNext()).

ArrayList Algorithms

Search: linear search with get(). Sort: Collections.sort(list). Min/max: Collections.min/max(list).

Removing Elements

remove(index): removes and shifts. remove(Object): removes first match. Modifying while iterating: use iterator.remove().

Unit 7 Summary

ArrayList dynamic, resizable. Methods: add, remove, get, size. Type parameter specifies element type. Autoboxing converts primitives.

More AP Computer Science A guides

• Primitives
• Using Objects
• Boolean Expressions
• Loops
• Writing Classes