ALists, Resizing, vs SLists

Why Array Lists

Arbitrary Retrieval

• Linked list slow get(int i) for long lists

Naive Array Lists

Random Access in Arrays

• Retrieval from any position of array very fast
  • Independent* of array size
    • When array gets too big, sometimes pushed onto slower parts of computer's memory/disk drive
  • Fast random access b/c memory boxes same size (in bits)

Making AList Fast

Memory Efficiency

• Define "usage ratio"/load factor, R = size / items.length;
• Half array size when R < .25

Generic ALists

• Generic arrays not allowed in Java
• Need to use (Item[]) new Object[100];

Nulling Out Deleted Items

• Unlike integer based ALists, actually want to null out deleted items
• Keeping references to unneeded objects = loitering