Placement & Statics
Put every function in the class most interested in it, and keep static methods truly stateless utilities.
Misplaced Responsibility
G17: Every piece of code should live where a reader would naturally look for it. When you write a method on Order that only reads Inventory data, you've misplaced it. The reader looking at Inventory won't find a method that belongs there. The method has a natural home — put it there. The rule of thumb: a method belongs in the class whose data it uses most.
Inappropriate Static Methods
G18: Static methods are fine for pure utilities that have no need for polymorphism — Math.round, String.format. They become a problem when the method should be polymorphic. If you have Order.calculateFee(order) as a static and tomorrow you need RushOrder to calculate fees differently, you're stuck. Instance methods support overriding; static methods do not. Reserve statics for operations that will never need specialization.
Code Challenge
Move the reorder_needed method to the Inventory class where it belongs.
💡Key takeaway
Put code where a reader would naturally look for it — in the class most interested in the data it uses.
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Hint: G17/G18: Ask which class is most interested in this data. Move the method there.
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