How do their APIs compare?

Good comparison question since these two libraries operate at completely different layers, but I can contrast what's visible in the data.

karumi/dexter — Android runtime-permissions API

Dexter exposes a small, fluent builder-style API oriented around a single concern: requesting Android runtime permissions.

• Entry point: Dexter.withContext(activity) chained with .withPermission(permission) (or presumably a multi-permission variant), .withListener(listener), and .check() to trigger the actual request, as shown in the README usage example [README.md:L1-L20 excerpt / usage section].
• Callback-based results: Rather than returning a value synchronously (impossible given Android's async permission dialog), Dexter uses listener interfaces:
  • PermissionListener for single permissions, with onPermissionGranted(PermissionGrantedResponse), onPermissionDenied(PermissionDeniedResponse), and onPermissionRationaleShouldBeShown(PermissionRequest, PermissionToken) [README.md:L174-L186].
  • MultiplePermissionsListener for batches, backed by MultiplePermissionsReport [dexter/src/main/java/com/karumi/dexter/listener/multi/BaseMultiplePermissionsListener.java:L1-L27].
• Convenience base classes: BasePermissionListener [dexter/src/main/java/com/karumi/dexter/listener/single/BasePermissionListener.java:L1-L27] and BaseMultiplePermissionsListener let consumers override only the callbacks they care about, rather than implementing every interface method.
• **Control-flow token:[REDACTED] PermissionToken.continuePermissionRequest() is a distinctive API idiom — because Android pauses the request pipeline while a rationale is being shown, Dexter forces the caller to explicitly resume the flow via this token, blocking further Dexter calls until it's invoked [README.md:L174-L186].

Overall, Dexter's API surface is narrow, synchronous-looking (fluent chain) but async in effect, and entirely UI/permission-domain specific.

netflix/hystrix — resilience/circuit-breaker API

Hystrix's API is broader and infrastructure-oriented, aimed at wrapping arbitrary remote calls with fault tolerance. From the retrieved data, the surface includes:

• Command/closure abstractions: ClosureCommand, ClosureFactory/AsyncClosureFactory [hystrix-contrib/hystrix-javanica/.../AsyncClosureFactory.java:L1-L23], and Closure (wrapping a Method + instance) [.../closure/Closure.java:L1-L23] — these back the Javanica annotation-driven module, letting methods be turned into Hystrix commands via reflection rather than manual subclassing.
• Caching support: HystrixGeneratedCacheKey / DefaultHystrixGeneratedCacheKey for request caching keys [.../cache/DefaultHystrixGeneratedCacheKey.java:L1-L24], plus a dedicated exception type HystrixCacheKeyGenerationException for cache-key generation failures [.../exception/HystrixCacheKeyGenerationException.java:L1-L22].
• Metrics-as-streams architecture: Per the 1.5.0 changelog, Hystrix moved from aggregate structures (HystrixRollingNumber, HystrixRollingPercentile) toward stream-based primitives like HystrixCommandCompletionStream, letting consumers aggregate metrics however they want, including off-box [CHANGELOG.md:L207-L224].
• Request-context lifecycle API: HystrixRequestContext was changed to implement Closeable [CHANGELOG.md:L200-L206], aligning it with Java's try-with-resources idiom.

Contrast