ArrayList vs LinkedList in Java: Complete Comparison

Both ArrayList and LinkedList implement the List interface, so they expose the same methods — the difference is how they store data internally. ArrayList is backed by a resizable array. element references occupy consecutive slots in the backing array, so getting an element by index is a direct calculation, which is constant time. The downside is inserting or removing in the middle, because everything after that point has to shift, which is linear time. When the array fills up, ArrayList grows by about fifty percent and copies into a bigger array. LinkedList is a doubly linked list. Each element lives in a node that holds the value plus references to the previous and next nodes. Because there's no index math, reaching position i means walking i nodes, so random access is linear time. But adding or removing at the head or tail is constant time, since you just relink a couple of references. Here's the subtle point interviewers love: even LinkedList's middle insertion is linear time, because you first have to traverse to the spot before you relink. In practice, ArrayList wins almost every time. Its a compact backing array of references means great cache locality, so iteration is much faster, and it uses far less memory per element — just one reference versus a node with two references. LinkedList only shines when you do lots of head and tail operations and rarely index. And even then, for a queue or stack, the modern choice is ArrayDeque, which is array-backed and beats LinkedList on both speed and memory. So my default is ArrayList, and I reach for ArrayDeque when I need queue behavior.