### Question:
AmazonWebServiceClient { protected void setEndpointPrefix(String endpointPrefix) { if (endpointPrefix == null) { throw new IllegalArgumentException( "The parameter endpointPrefix must be specified!"); } this.endpointPrefix = endpointPrefix; } AmazonWebServiceClient(ClientConfiguration clientConfiguration);  AmazonWebServiceClient(ClientConfiguration clientConfiguration,
            RequestMetricCollector requestMetricCollector); @SdkProtectedApi protected  AmazonWebServiceClient(ClientConfiguration clientConfiguration,
                                     RequestMetricCollector requestMetricCollector,
                                     boolean disableStrictHostNameVerification); protected  AmazonWebServiceClient(AwsSyncClientParams clientParams); @Deprecated void setEndpoint(String endpoint); Signer getSignerByURI(URI uri); @Deprecated void setRegion(Region region); @Deprecated final void configureRegion(Regions region); void shutdown(); @Deprecated void addRequestHandler(RequestHandler requestHandler); @Deprecated void addRequestHandler(RequestHandler2 requestHandler2); @Deprecated void removeRequestHandler(RequestHandler requestHandler); @Deprecated void removeRequestHandler(RequestHandler2 requestHandler2); void setTimeOffset(int timeOffset); AmazonWebServiceClient withTimeOffset(int timeOffset); int getTimeOffset(); RequestMetricCollector getRequestMetricsCollector(); String getServiceName(); String getEndpointPrefix(); final void setServiceNameIntern(String serviceName); final String getSignerRegionOverride(); final void setSignerRegionOverride(String signerRegionOverride); @Deprecated T withRegion(Region region); @Deprecated T withRegion(Regions region); @Deprecated T withEndpoint(String endpoint); @Deprecated @SdkInternalApi final void makeImmutable(); String getSignerOverride(); ClientConfiguration getClientConfiguration(); @Deprecated
    static final boolean LOGGING_AWS_REQUEST_METRIC; }### Answer:
@Test public void setEndpointPrefix() { AmazonTestClient client = new AmazonTestClient(); Assert.assertEquals(client.getServiceName(), client.getEndpointPrefix()); String endpointPrefixOverride = "foo"; Assert.assertNotEquals(endpointPrefixOverride, client.getServiceName()); client.setEndpointPrefix(endpointPrefixOverride); Assert.assertEquals(endpointPrefixOverride, client.getEndpointPrefix()); Assert.assertNotEquals(client.getEndpointPrefix(), client.getServiceName()); }