-optimizationpasses 5
-dontusemixedcaseclassnames
-dontskipnonpubliclibraryclasses
-dontpreverify
-verbose
-optimizations !code/simplification/arithmetic,!field/*,!class/merging/*

-keep public class * extends android.app.Activity
-keep public class * extends android.app.Application
-keep public class * extends android.app.Service
-keep public class * extends android.content.BroadcastReceiver
-keep public class * extends android.content.ContentProvider
-keep public class * extends android.app.backup.BackupAgentHelper
-keep public class * extends android.preference.Preference
-keep public class com.android.vending.licensing.ILicensingService

-keepclasseswithmembernames class * {
    native <methods>;
}

-keepclasseswithmembers class * {
    public <init>(android.content.Context, android.util.AttributeSet);
}

-keepclasseswithmembers class * {
    public <init>(android.content.Context, android.util.AttributeSet, int);
}

-keepclassmembers class * extends android.app.Activity {
   public void *(android.view.View);
}

-keepclassmembers enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

-keep class * implements android.os.Parcelable {
  public static final android.os.Parcelable$Creator *;
}

		Random rand = new Random();
		int i = rand.nextInt() % 256; // range -255  +255
		System.out.print(i + "

"); // -184
		i = Math.abs(rand.nextInt() % 12); // range 0  +11
		System.out.print(i); // 7

// Math.random() start with 0.  e.g. 0.35981234 
int nRan = (int) (Math.random()*10); // 0 - 10

// nextDouble(), nextFloat(), nextInt(), nextLong() returns 0 - 10
import java.util.Random;´

Random r = new Random();
int nRan = r.nextInt(); // 0 - 10
double dRan = r.nextDouble() * 10; // e.g. 7.496285271597397

nextDouble – return 0 - 1
nextFloat – same as double
nextInt –  -2147483648  +2147483647
nextLong –  -922337203685775808  +9223372036854775807
nextGaussian –  0.0 aberation 1.0.

String sFileContent = readFile("myfile.txt",StandardCharsets.UTF_8);

	static String readFile(String path, Charset encoding) 
		  throws IOException 
		{
		  byte[] encoded = Files.readAllBytes(Paths.get(path));
		  return encoding.decode(ByteBuffer.wrap(encoded)).toString();
		}

// write file
String sOut = "text blah hello world etc.";
		writeToFile(sOut"someName.txt");	
	static void writeToFile(String sB,String name) {
		String folder = ("c:\\folder\");
		File f = new File(folder+ name);
		BufferedWriter writer = null;
			writer = new BufferedWriter( new OutputStreamWriter(
                           new FileOutputStream( folder+name),"UTF-8"));
			writer.write( sB);

				if ( writer != null)
					writer.close( );
	}