package com.asynctaskexample;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.ProgressBar;
import android.widget.TextView;

public class MainActivity extends Activity {
	private TextView textView;
	private ProgressBar progressBar;
	private DownloadWebPageTask mTask = null;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		textView = (TextView) findViewById(R.id.TextView01);
		downloadPage();
	}

	// AsyncTask <TypeOfVarArgParams , ProgressValue , ResultValue> .
	private class DownloadWebPageTask extends AsyncTask<String, Integer, String> {

		@Override
		protected void onPreExecute() {
			//textView.setText("Hello !!!");
			progressBar = (ProgressBar) findViewById(R.id.progressBar1);
			progressBar.setVisibility(View.VISIBLE);
			super.onPreExecute();
		}

		@Override
		protected void onProgressUpdate(Integer... values) {
			super.onProgressUpdate(values);

		}

		@Override
		protected String doInBackground(String... urls) {
			String response = "";
			for (String url : urls) {
				DefaultHttpClient client = new DefaultHttpClient();
				HttpGet httpGet = new HttpGet(url);
				try {
					HttpResponse execute = client.execute(httpGet);
					InputStream content = execute.getEntity().getContent();

					BufferedReader buffer = new BufferedReader(new InputStreamReader(
							content));
					String s = "";
					while ((s = buffer.readLine()) != null) {
						response += s;
					}

				} catch (Exception e) {
					e.printStackTrace();
				}
			}
			return response;
		}

		@Override
		protected void onPostExecute(String result) {
			progressBar.setVisibility(View.INVISIBLE);
			textView.setText(result);
		}
	}

	private void downloadPage() {
		if (mTask != null
				&& mTask.getStatus() != DownloadWebPageTask.Status.FINISHED) {
			mTask.cancel(true);
		}
               // execute(String[]) you can put array of links to web pages, or array of Integer[] 
               // if first param is Integer[] etc.
		mTask = (DownloadWebPageTask) new DownloadWebPageTask()
				.execute(new String[] { "//android.okhelp.cz/android-market.html",
						"//android.okhelp.cz/android-market.html" });
	}

	@Override
	protected void onDestroy() {
		super.onDestroy();

		if (mTask != null
				&& mTask.getStatus() != DownloadWebPageTask.Status.FINISHED) {
			mTask.cancel(true);
			mTask = null;
		}
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.activity_main, menu);
		return true;
	}

}

<LinearLayout xmlns:android="//schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ProgressBar
        android:id="@+id/progressBar1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/TextView01"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

</LinearLayout>

<uses-permission android:name="android.permission.INTERNET" />

// file name MyFirstClass.java

import java.util.*;
import java.lang.Math;
import java.io.*;
import javax.swing.*;

public class MyFirstClass{ // start of program
  public static void main(String[] args) { // basic  function main

// variables and calculation
int a=2;
int b=3;
int c=Integer.parseInt(JOptionPane.showInputDialog(" Put number: ", "1"));
System.out.println("Number is: "+c);
System.out.println(a+" * "+b+" = "+(a*b));
System.out.println("a^3 "+Math.pow(a,b));

//array
int[] array_my=new int[10];
array_my[0]=3;
array_my[1]=5;
System.out.println("Number of elements "+array_my.length+" 1 + 2 element of array "+(array_my[0]+array_my[1]));

//strings
String txt="Quick red fox";
String txt2=JOptionPane.showInputDialog("Write text: ", "word");
System.out.println("Text is: "+txt2);
String[] count_of_word=txt.split(" ");
System.out.println("Length: "+txt.length()+" Count of words "+count_of_word.length);
System.out.println(txt +" -> "+txt.replace("red","brown"));
System.out.println("First 5 chars of string is: "+ txt.substring(0,5));

//for a if
for(int i=0; i<10;i++){
	if(i==3)System.out.println("i equal "+i);
	}

// file
try {
  File soubor=new File("some_file.txt");
  if(!soubor.exists()){
	System.out.println("File dont exist");
  }
  else { // utf-8 encoding
    BufferedReader in1 = new BufferedReader(new InputStreamReader(new FileInputStream(soubor),"UTF-8"));
    BufferedWriter out1 = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("zapis.txt"),"UTF-8"));
    String str;
      while ((str = in1.readLine())!=null){
        System.out.println(str);
        out1.write(str+"

");
      }
    in1.close();
    out1.close();
   }
 } catch(IOException e){System.out.println("Error " + e);}

// dir
 File pathName = new File("some_dir");
 String[] fileNames = pathName.list();
 if(pathName.exists())
 System.out.println("Name of first file in  "some_dir": "+fileNames[0]);
 else System.out.println("dir not exist");

//function
int nResult = calculateMyFc(3,5);
System.out.println("Result of function: "+nResult);

} // end of function main

// new function , you can add to end MyFc = my function
public static int calculateMyFc(int a, int b){
return (a+b);
}

} // end of class of program