Table of contents

Why does Map exist?

What would life be without it?

HashMap: the street analogy

hashCode() and equals() explained

Collisions: when two people share a house

Load factor and resizing

The other Map types

The one rule you must never break

Interview problems where Map is the answer

SECTION 1.

Why does Map even exist?

Before touching any internals, let's nail the real problem Map was built to solve because if you understand the problem, everything else makes sense automatically.

Imagine you work at a hotel front desk. 1,000 guests are checked in. Your boss walks over and asks:

The scenario "Is John Smith in room 847?"

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You have two choices for how to answer that.

The hook label is the key. The room key hanging on it is the value.…