package com.sunmeat.files;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Toast;

import java.io.FilterReader;
import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;

class MakeUpperCase extends FilterReader {

    protected MakeUpperCase(Reader r) {
        super(r);
        // Implicit super constructor FilterReader() is undefined for default
        // constructor. Must define an explicit constructor!
    }

    @Override
    public int read() throws IOException {
        int c = super.read(); // Returns:
        // The character read, as an integer in the range 0 to 65535,
        // or -1 if the end of the stream has been reached
        return (c == -1 ? c : Character.toUpperCase((char) c));
    }

    @Override
    public int read(char[] buf, int offset, int count) throws IOException {
        int nread = super.read(buf, offset, count);
        int last = offset + nread;
        for (int i = offset; i < last; i++) {
            buf[i] = Character.toUpperCase(buf[i]);
        }
        return nread;
    }

}

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void writeFile(View v) {

        StringBuilder sb = new StringBuilder(50);

        try {
            StringReader src = new StringReader("Test String!");

            // abstract class for reading filtered character streams
            FilterReader f = new MakeUpperCase(src);
            int c;
            while ((c = f.read()) != -1) {
                sb.append((char)c);
            }
            Toast.makeText(this, sb.toString(), Toast.LENGTH_SHORT).show();

        } catch (IOException e) {
            Toast.makeText(this, "IOException!", Toast.LENGTH_SHORT).show();
        }
    }
}