Test.kt

  @Test
  fun closeAJarFileWhileSomebodyIsReadingIt() {
    val someJarResource = this::class.java.classLoader.getResource("LICENSE-junit.txt")!!

    val connectionA = someJarResource.openConnection()
    val sourceA = connectionA.getInputStream().source().buffer()

    val connectionB = someJarResource.openConnection()
    val sourceB = connectionB.getInputStream().source().buffer()

    connectionA.useCaches = false
    assertThat(sourceA.readUtf8()).contains("JUnit")
    sourceA.close()

    assertThat(sourceB.readUtf8()).contains("JUnit")
    sourceB.close()
  }

It doesn’t crash if you remove this line:

connectionA.useCaches = false

And it doesn’t crash if you don’t open sourceB until after closing sourceA.

Setting useCaches to false causes sourceA to close a .jar file that it doesn’t own.

awesome! explains the race condition