Creating an Array and Indexing from Zero

A single variable can only hold one value, so storing a hundred scores would normally mean a hundred names. An array solves this by reserving one block of memory sliced into equal-sized slots, all under one name, each slot holding one value of the same type. You reach any slot instantly with an index in square brackets, like scores[3], instead of needing a different variable for every value.

This works because the array stores its elements contiguously, back to back in memory. Once Java knows where the array starts and how big each slot is, it can jump straight to any element by adding the index to the starting position — no searching, no stepping through the others first. That's why indexing is a single, fast step no matter how large the array is.

The index is really an offset: how many slots over from the first one. The first element needs 0 slots of movement to reach itself, so it lives at index 0, and an array of length 5 fills indices 0 through 4 — the last legal index is always length - 1, not length. This offset view of indexing carries straight into grids in the next topic, where a 2D array needs two offsets, one for row and one for column, to land on a single cell.