1Z0-829 Working with Streams and Lambda Expressions Practice Question
A company needs to process a stream of orders and filter out orders that are not in the 'SHIPPED' status. Then they want to collect the order IDs into a list. Which of the following correctly uses lambda expressions to achieve this?
⚠ Common exam trap
Oracle often tests the distinction between using equals() vs == for string comparison in lambda expressions, and the correct order of stream operations (filter before map) to avoid type mismatches or logical errors.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
orders.stream().filter(o -> o.getStatus().equals("SHIPPED")).map(Order::getId).collect(Collectors.toList())
It first filters the stream to include only orders with status 'SHIPPED' using a lambda expression that calls equals() on the status string, then maps each order to its ID using a method reference, and finally collects the IDs into a list. This correctly uses lambda expressions and the Stream API to achieve the requirement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
orders.stream().filter(o -> o.getStatus() != "SHIPPED").map(Order::getId).collect(Collectors.toList())
Why it's wrong here
Filters out SHIPPED orders instead of keeping them.
- ✗
orders.stream().map(Order::getId).filter(id -> id.equals("SHIPPED")).collect(Collectors.toList())
Why it's wrong here
Filters IDs, but IDs are not status strings.
- ✗
orders.stream().filter(Order::getStatus).map(o -> o.getId()).collect(Collectors.toList())
Why it's wrong here
filter expects a Predicate<Order>, but getStatus returns String, not boolean.
- ✓
orders.stream().filter(o -> o.getStatus().equals("SHIPPED")).map(Order::getId).collect(Collectors.toList())
Why this is correct
Correctly filters SHIPPED orders and maps to IDs.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
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