Handle 'System.exit' in exercise 8 chapter3

src/main/scala/org/learningconcurrency/exercises/ch3/ex8.scala

@@ -21,6 +21,8 @@ object Ex8 extends App {
 
   // This method's preconditions are the following:
   //   - In case of executing in sbt, set `fork` setting to `true` (set fork := true ).
+  //
+  // If passed block which contains `System.exit`, this method throws `SecurityException`.
   def spawn[T](block: => T): T = {
     val className = Ex8_EvaluationApp.getClass().getName().split((Pattern.quote("$")))(0)
     val tmp = File.createTempFile("concurrent-programming-in-scala", null)
@@ -62,4 +64,13 @@ object Ex8 extends App {
     case e: NumberFormatException =>
     case _: Throwable => assert(false)
   }
+
+  try {
+    spawn({
+      System.exit(0)
+    })
+  } catch {
+    case e: SecurityException =>
+    case _: Throwable => assert(false)
+  }
 }

src/main/scala/org/learningconcurrency/exercises/ch3/ex8_evaluationapp.scala

@@ -6,10 +6,20 @@ import java.io.FileInputStream
 import java.io.FileOutputStream
 import java.io.ObjectInputStream
 import java.io.ObjectOutputStream
+import java.security.Permission
 
 // This application receives the file path in which the serialized `Function0` object has been written.
 // Then, it reads and evaluates serialized `Function0` object, finally overwrites its result to the same file.
 object Ex8_EvaluationApp extends App {
+  System.setSecurityManager(new SecurityManager() {
+    // allows access to file.
+    override def checkPermission(perm: Permission): Unit = {}
+    // detects `System.exit` in order not to be halted by the caller.
+    override def checkExit(status: Int): Unit = {
+      throw new SecurityException("not allowed to pass a block which contains System.exit(int) !")
+    }
+  });
+
   val path = args(0)
 
   val in = new ObjectInputStream(new FileInputStream(path))