For permission issues, I encourage you to use an external storage such as an SD card.
Environment.getExternalStorageDirectory()
you can create a folder there and save your files. You can also use "/data/local/" if your system permits user files to be saved there. You can refer to this page regarding the various ways you can save files to internal and external storage,
For the second problem I suggest you to use DataInputStream,
File file = new File("myFile");
byte[] fileData = new byte[(int) file.length()];
DataInputStream dis = new DataInputStream(new FileInputStream(file));
dis.readFully(fileData);
dis.close();
You can code something like this,
import java.io.*;
public class Sequence {
public static void main(String[] args) throws IOException {
DataInputStream dis = new DataInputStream(System.in);
String str="Enter your Age :";
System.out.print(str);
int i=dis.readInt();
System.out.println((int)i);
}
}
You can also Use Serializable interface for reading and writing serializable objects. In fact, I used this once when I tried to write data values directly to files instead of any traditional databases (In my very first undergraduate years, I was not familiar with databases). A good example is here,
import java.io.*;
import java.util.*;
import java.util.logging.*;
/** JDK before version 7. */
public class ExerciseSerializable {
public static void main(String... aArguments) {
//create a Serializable List
List<String> quarks = Arrays.asList(
"up", "down", "strange", "charm", "top", "bottom"
);
//serialize the List
//note the use of abstract base class references
try{
//use buffering
OutputStream file = new FileOutputStream("quarks.ser");
OutputStream buffer = new BufferedOutputStream(file);
ObjectOutput output = new ObjectOutputStream(buffer);
try{
output.writeObject(quarks);
}
finally{
output.close();
}
}
catch(IOException ex){
fLogger.log(Level.SEVERE, "Cannot perform output.", ex);
}
//deserialize the quarks.ser file
//note the use of abstract base class references
try{
//use buffering
InputStream file = new FileInputStream("quarks.ser");
InputStream buffer = new BufferedInputStream(file);
ObjectInput input = new ObjectInputStream (buffer);
try{
//deserialize the List
List<String> recoveredQuarks = (List<String>)input.readObject();
//display its data
for(String quark: recoveredQuarks){
System.out.println("Recovered Quark: " + quark);
}
}
finally{
input.close();
}
}
catch(ClassNotFoundException ex){
fLogger.log(Level.SEVERE, "Cannot perform input. Class not found.", ex);
}
catch(IOException ex){
fLogger.log(Level.SEVERE, "Cannot perform input.", ex);
}
}
// PRIVATE
//Use Java's logging facilities to record exceptions.
//The behavior of the logger can be configured through a
//text file, or programmatically through the logging API.
private static final Logger fLogger =
Logger.getLogger(ExerciseSerializable.class.getPackage().getName())
;
}