[SPARK-14914][CORE] Fix Resource not closed after using, mostly for unit tests

## What changes were proposed in this pull request?

Close `FileStreams`, `ZipFiles` etc to release the resources after using. Not closing the resources will cause IO Exception to be raised while deleting temp files.
## How was this patch tested?

Existing tests

Author: U-FAREAST\tl <tl@microsoft.com>
Author: hyukjinkwon <gurwls223@gmail.com>
Author: Tao LI <tl@microsoft.com>

Closes #15618 from HyukjinKwon/SPARK-14914-1.

1 files changed, 10 insertions, 6 deletions

diff --git a/mllib/src/test/scala/org/apache/spark/mllib/util/MLUtilsSuite.scala b/mllib/src/test/scala/org/apache/spark/mllib/util/MLUtilsSuite.scala
index e4e9be39ff..665708a780 100644
--- a/mllib/src/test/scala/org/apache/spark/mllib/util/MLUtilsSuite.scala
+++ b/mllib/src/test/scala/org/apache/spark/mllib/util/MLUtilsSuite.scala
@@ -155,13 +155,17 @@ class MLUtilsSuite extends SparkFunSuite with MLlibTestSparkContext {
     val tempDir = Utils.createTempDir()
     val outputDir = new File(tempDir, "output")
     MLUtils.saveAsLibSVMFile(examples, outputDir.toURI.toString)
-    val lines = outputDir.listFiles()
+    val sources = outputDir.listFiles()
       .filter(_.getName.startsWith("part-"))
-      .flatMap(Source.fromFile(_).getLines())
-      .toSet
-    val expected = Set("1.1 1:1.23 3:4.56", "0.0 1:1.01 2:2.02 3:3.03")
-    assert(lines === expected)
-    Utils.deleteRecursively(tempDir)
+      .map(Source.fromFile)
+    Utils.tryWithSafeFinally {
+      val lines = sources.flatMap(_.getLines()).toSet
+      val expected = Set("1.1 1:1.23 3:4.56", "0.0 1:1.01 2:2.02 3:3.03")
+      assert(lines === expected)
+    } {
+      sources.foreach(_.close())
+      Utils.deleteRecursively(tempDir)
+    }
   }
 
   test("appendBias") {