1Z0-829 Working with Streams and Lambda Expressions Practice Question
A lambda that takes a String and returns its length is assigned to which functional interface?
⚠ Common exam trap
Many candidates confuse `UnaryOperator` (which requires same input/output type) with `Function` (which allows different types), leading them to pick A instead of E.
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
✓
Function<String, Integer>
The lambda `(String s) -> s.length()` takes a `String` input and returns an `Integer` (the length). This matches the `Function<T, R>` functional interface, which defines the abstract method `R apply(T t)`. Option E is correct because `Function<String, Integer>` exactly represents a function that accepts a `String` and produces an `Integer`.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
UnaryOperator<String>
Why it's wrong here
UnaryOperator takes and returns the same type.
- ✗
Consumer<String>
Why it's wrong here
Consumer takes a value and returns void.
- ✗
Predicate<String>
Why it's wrong here
Predicate returns a boolean.
- ✗
Supplier<Integer>
Why it's wrong here
Supplier takes no arguments and returns a value.
- ✓
Function<String, Integer>
Why this is correct
Correct. This functional interface accepts a String and returns an Integer.
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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