Must-do problems: Object Class and Equality

130 min · Intermediate

Back to syllabus (Object Class & Equality)

Every problem here asks you to decide what "equal" means for a small class and to write toString(), equals() and hashCode() that agree with each other. Read the input with Scanner, compare objects with equals() (never == for data), and run every test before you open a hint.

What you will learn

Override toString(), equals() and hashCode() together in real classes
Choose the fields that define equality, including a stable id
Use equals() and hashCode() to find duplicates and look objects up
Build a small hash table that relies on the equals/hashCode contract

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