trying to fix the threadexecutor, at least it will throw error if a job failed

src/net/torvald/terrarum/concurrent/ThreadParallel.kt

@@ -1,9 +1,6 @@
 package net.torvald.terrarum.concurrent
 
-import java.util.concurrent.ExecutorService
-import java.util.concurrent.Executors
-import java.util.concurrent.Future
-import java.util.concurrent.TimeUnit
+import java.util.concurrent.*
 import kotlin.math.absoluteValue
 
 typealias RunnableFun = () -> Unit
@@ -14,32 +11,58 @@ typealias ThreadableFun = (Int) -> Unit
 object ThreadExecutor {
     val threadCount = Runtime.getRuntime().availableProcessors() // not using (logicalCores + 1) method; it's often better idea to reserve one extra thread for other jobs in the app
     private lateinit var executor: ExecutorService// = Executors.newFixedThreadPool(threadCount)
+    val futures = ArrayList<Future<*>>()
+    private var isOpen = true
 
     private fun checkShutdown() {
         try {
             if (executor.isTerminated)
                 throw IllegalStateException("Executor terminated, renew the executor service.")
-            if (executor.isShutdown)
+            if (!isOpen || executor.isShutdown)
                 throw IllegalStateException("Pool is closed, come back when all the threads are terminated.")
         }
         catch (e: UninitializedPropertyAccessException) {}
     }
 
     fun renew() {
+        try {
+            if (!executor.isTerminated && !executor.isShutdown) throw IllegalStateException("Pool is still running")
+        }
+        catch (_: UninitializedPropertyAccessException) {}
+
         executor = Executors.newFixedThreadPool(threadCount)
+        futures.clear()
+        isOpen = true
     }
 
-    fun submit(t: Runnable): Future<*> {
+    /*fun invokeAll(ts: List<Callable<Unit>>) {
         checkShutdown()
-        return executor.submit(t)
-    }
-    fun submit(f: RunnableFun): Future<*> {
-        checkShutdown()
-        return executor.submit { f() }
-    }
+        executor.invokeAll(ts)
+    }*/
 
+    fun submit(t: Callable<Unit>) {
+        checkShutdown()
+        val fut = executor.submit(t)
+        futures.add(fut)
+    }
+    /*fun submit(f: RunnableFun) {
+        checkShutdown()
+        val fut = executor.submit { f() }
+        futures.add(fut)
+    }*/
+
+    // https://stackoverflow.com/questions/28818494/threads-stopping-prematurely-for-certain-values
     fun join() {
         println("ThreadExecutor.join")
+        isOpen = false
+        futures.forEach {
+            try {
+                it.get()
+            }
+            catch (e: ExecutionException) {
+                throw e
+            }
+        }
         executor.shutdown() // thread status of completed ones will be WAIT instead of TERMINATED without this line...
         executor.awaitTermination(24L, TimeUnit.HOURS)
     }

src/net/torvald/terrarum/modulebasegame/worldgenerator/Biomegen.kt

@@ -23,21 +23,13 @@ class Biomegen(world: GameWorld, seed: Long, params: Any) : Gen(world, seed, par
 
     private val genSlices = maxOf(ThreadExecutor.threadCount, world.width / 8)
 
-    private var genFutures: Array<Future<*>?> = arrayOfNulls(genSlices)
-    override var generationStarted: Boolean = false
-    override val generationDone: Boolean
-        get() = generationStarted && genFutures.fold(true) { acc, f -> acc and (f?.isDone ?: true) }
-
     private val YHEIGHT_MAGIC = 2800.0 / 3.0
     private val YHEIGHT_DIVISOR = 2.0 / 7.0
 
-    override fun run() {
-
-        generationStarted = true
-
+    override fun getDone() {
         ThreadExecutor.renew()
-        (0 until world.width).sliceEvenly(genSlices).mapIndexed { i, xs ->
-            genFutures[i] = ThreadExecutor.submit {
+        (0 until world.width).sliceEvenly(genSlices).map { xs ->
+            ThreadExecutor.submit {
                 val localJoise = getGenerator(seed, params as BiomegenParams)
                 for (x in xs) {
                     for (y in 0 until world.height) {

src/net/torvald/terrarum/modulebasegame/worldgenerator/Terragen.kt

@@ -20,33 +20,28 @@ class Terragen(world: GameWorld, seed: Long, params: Any) : Gen(world, seed, par
 
     private val genSlices = maxOf(ThreadExecutor.threadCount, world.width / 8)
 
-    private var genFutures: Array<Future<*>?> = arrayOfNulls(genSlices)
-    override var generationStarted: Boolean = false
-    override val generationDone: Boolean
-        get() = generationStarted && genFutures.fold(true) { acc, f -> acc and (f?.isDone ?: true) }
-
     private val YHEIGHT_MAGIC = 2800.0 / 3.0
     private val YHEIGHT_DIVISOR = 2.0 / 7.0
 
-    override fun run() {
-
-        generationStarted = true
-
+    override fun getDone() {
         ThreadExecutor.renew()
         (0 until world.width).sliceEvenly(genSlices).mapIndexed { i, xs ->
-            genFutures[i] = ThreadExecutor.submit {
+            ThreadExecutor.submit {
                 val localJoise = getGenerator(seed, params as TerragenParams)
-                for (x in xs) {
-                    for (y in 0 until world.height) {
-                        val sampleTheta = (x.toDouble() / world.width) * TWO_PI
-                        val sampleOffset = world.width / 8.0
-                        val sampleX = sin(sampleTheta) * sampleOffset + sampleOffset // plus sampleOffset to make only
-                        val sampleZ = cos(sampleTheta) * sampleOffset + sampleOffset // positive points are to be sampled
-                        val sampleY = y - (world.height - YHEIGHT_MAGIC) * YHEIGHT_DIVISOR // Q&D offsetting to make ratio of sky:ground to be constant
-                        // DEBUG NOTE: it is the OFFSET FROM THE IDEAL VALUE (observed land height - (HEIGHT * DIVISOR)) that must be constant
-                        val noise = localJoise.map { it.get(sampleX, sampleY, sampleZ) }
+                val localLock = java.lang.Object() // in an attempt to fix the "premature exit" issue of a thread run
+                synchronized(localLock) {          // also see: https://stackoverflow.com/questions/28818494/threads-stopping-prematurely-for-certain-values
+                    for (x in xs) {
+                        for (y in 0 until world.height) {
+                            val sampleTheta = (x.toDouble() / world.width) * TWO_PI
+                            val sampleOffset = world.width / 8.0
+                            val sampleX = sin(sampleTheta) * sampleOffset + sampleOffset // plus sampleOffset to make only
+                            val sampleZ = cos(sampleTheta) * sampleOffset + sampleOffset // positive points are to be sampled
+                            val sampleY = y - (world.height - YHEIGHT_MAGIC) * YHEIGHT_DIVISOR // Q&D offsetting to make ratio of sky:ground to be constant
+                            // DEBUG NOTE: it is the OFFSET FROM THE IDEAL VALUE (observed land height - (HEIGHT * DIVISOR)) that must be constant
+                            val noise = localJoise.map { it.get(sampleX, sampleY, sampleZ) }
 
-                        draw(x, y, noise, world)
+                            draw(x, y, noise, world)
+                        }
                     }
                 }
             }

src/net/torvald/terrarum/modulebasegame/worldgenerator/Worldgen.kt

@@ -3,6 +3,7 @@ package net.torvald.terrarum.modulebasegame.worldgenerator
 import net.torvald.terrarum.AppLoader
 import net.torvald.terrarum.AppLoader.printdbg
 import net.torvald.terrarum.gameworld.GameWorld
+import java.util.concurrent.Callable
 
 /**
  * New world generator.
@@ -34,7 +35,7 @@ object Worldgen {
             val it = jobs[i]
 
             AppLoader.getLoadScreen().addMessage(it.loadingScreenName)
-            it.theWork.run()
+            it.theWork.getDone()
         }
 
         printdbg(this, "Generation job finished")
@@ -46,9 +47,7 @@ object Worldgen {
 }
 
 abstract class Gen(val world: GameWorld, val seed: Long, val params: Any) {
-    abstract var generationStarted: Boolean
-    abstract val generationDone: Boolean
-    open fun run() { }
+    open fun getDone() { } // trying to use different name so that it won't be confused with Runnable or Callable
 }
 
 data class WorldgenParams(