Issue 4231 - Fix unstable FilterEngineTest.testSetRemoveFilterChangeCallback

libadblockplus-android/src/org/adblockplus/libadblockplus/FileSystemUtils.java

Index: libadblockplus-android/src/org/adblockplus/libadblockplus/FileSystemUtils.java
diff --git a/libadblockplus-android/src/org/adblockplus/libadblockplus/FileSystemUtils.java b/libadblockplus-android/src/org/adblockplus/libadblockplus/FileSystemUtils.java
new file mode 100644
index 0000000000000000000000000000000000000000..a16c4198c030206ef151aff9ad1654fdffa9521a
--- /dev/null
+++ b/libadblockplus-android/src/org/adblockplus/libadblockplus/FileSystemUtils.java
@@ -0,0 +1,115 @@
+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-2017 eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.adblockplus.libadblockplus;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.NoSuchElementException;
+import java.util.Scanner;
+import java.util.UUID;
+
+public class FileSystemUtils
+{
+  /**
+   * Read all the file data to string
+   *
+   * @param file path to read data
+   * @return file data
+   * @throws java.io.FileNotFoundException
+   */
+  public static String readFile(File file) throws FileNotFoundException
+  {
+    Scanner scanner = null;
+    try
+    {
+      scanner = new Scanner(file);
+      return scanner.useDelimiter("\\A").next();
+    }
+    catch (NoSuchElementException e)
+    {
+      return "";
+    }
+    finally
+    {
+      if (scanner != null)
+      {
+        scanner.close();
+      }
+    }
+  }
+
+  /**
+   * Write data to file (with rewriting)
+   *
+   * @param file file
+   * @param data file data
+   */
+  public static void writeFile(File file, String data) throws IOException
+  {
+    FileOutputStream fos = null;
+    try
+    {
+      fos = new FileOutputStream(file);
+      if (data != null)
+      {
+        fos.write(data.getBytes());
+      }
+    }
+    finally
+    {
+      if (fos != null)
+      {
+        try
+        {
+          fos.close();
+        }
+        catch (IOException e)
+        {
+          // ignored
+        }
+      }
+    }
+  }
+
+  /**
+   * Generate unique filename
+   *
+   * @param prefix prefix
+   * @param suffix suffix
+   * @return generated unique filename
+   */
+  public static String generateUniqueFileName(String prefix, String suffix)
+  {
+    StringBuilder sb = new StringBuilder();
+    if (prefix != null)
+    {
+      sb.append(prefix);
+    }
+
+    sb.append(UUID.randomUUID().toString());
+
+    if (suffix != null)
+    {
+      sb.append(suffix);
+    }
+
+    return sb.toString();
+  }
+}