This has been observed once on Mac OS x. It is intermittent

java.net.BindException: Address already in use
at sun.nio.ch.Net.bind0(java.base@9-internal/Native Method)
at sun.nio.ch.Net.bind(java.base@9-internal/Net.java:433)
at sun.nio.ch.Net.bind(java.base@9-internal/Net.java:425)
at sun.nio.ch.ServerSocketChannelImpl.bind(java.base@9-internal/ServerSocketChannelImpl.java:225)
at sun.nio.ch.ServerSocketAdaptor.bind(java.base@9-internal/ServerSocketAdaptor.java:74)
at sun.net.httpserver.ServerImpl.<init>(jdk.httpserver@9-internal/ServerImpl.java:101)
at sun.net.httpserver.HttpServerImpl.<init>(jdk.httpserver@9-internal/HttpServerImpl.java:50)
at sun.net.httpserver.DefaultHttpServerProvider.createHttpServer(jdk.httpserver@9-internal/DefaultHttpServerProvider.java:35)
at com.sun.net.httpserver.HttpServer.create(jdk.httpserver@9-internal/HttpServer.java:129)
at SimpleHttpServerTest.main(SimpleHttpServerTest.java:52)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(java.base@9-internal/Native Method)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(java.base@9-internal/NativeMethodAccessorImpl.java:62)
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(java.base@9-internal/DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(java.base@9-internal/Method.java:535)
at com.sun.javatest.regtest.agent.MainActionHelper$SameVMRunnable.run(MainActionHelper.java:226)
at java.lang.Thread.run(java.base@9-internal/Thread.java:843)