Convert a Java loop to a stream without losing key order

About this exercise

Convert idsByCustomer to a single stream pipeline. The invoice printer relies on customers appearing in first-seen order, so the result must stay a LinkedHashMap. Also, from now on customer ids must be trimmed and upper-cased (the new import has values like ' acme '). Skip VOID orders as before, and now also skip test orders, which have cents of 0. Keep the signature. Return only the method in exactly 1 code block of at most 10 lines, with under 15 words of text.

Common mistakes when you ask AI for this

• Losing the order. A plain groupingBy returns a HashMap, so the invoice index comes out shuffled. Try: Add: "Keep first-seen order: groupingBy(key, LinkedHashMap::new, mapping(...))."
• Not mentioning the new rule. The AI only converts what's there; it can't know ids must now be cleaned. Try: Add: "Group by customerId().trim().toUpperCase()."
• Missing the test-order filter. The AI only keeps the VOID check it can see; it can't know 0-cent test orders must go. Try: Add: "Also skip orders with cents == 0. Keep the signature; one return statement."
• The whole class and a lecture. The AI reprints the class and explains streams. Try: Add: "Only the method, one code block, no text."

What a strong prompt includes

• Protects the order
• Gives the new id rule
• Adds the test-order filter
• Protects the signature
• Asks for only the method

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