Java Basic Rules
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// 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
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Example source code for Android developers how create array of strings in *.xml file.
You can using array of strings in Spinner ( combobox - dropdown list ) or ListView etc.
You can using array of strings in Spinner ( combobox - dropdown list ) or ListView etc.
<resources>
<string-array name="colors">
<item>red</item>
<item>orange</item>
<item>yellow</item>
<item>green</item>
<item>blue</item>
</string-array>
</resources>
Failed to rename directory ....
If using for update Android SDK manager,
try close Eclipse if is open.
Or change security settings of the folder which have problem.
Or disable antivirus for a moment.
If using for update Android SDK manager,
try close Eclipse if is open.
Or change security settings of the folder which have problem.
Or disable antivirus for a moment.
// Context instead Activity as a parameter
@Override
public void onAttach(Context context) {
super.onAttach(context);
Activity a;
if (context instanceof Activity){
a=(Activity) context;
}
}
OnNoteClickedListener listener;
/* old emxample of usage
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
listener = (OnNoteClickedListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnNoteClickedListener");
}
}
*/
// new version of code
@Override
public void onAttach(Context context) {
super.onAttach(context);
Activity a;
if (context instanceof Activity){
a=(Activity) context;
try {
listener = (OnNoteClickedListener) a;
} catch (ClassCastException e) {
throw new ClassCastException(a.toString()
+ " must implement OnNoteClickedListener");
}
}
}
Try this code with CursorLoader:
Uri uri = getIntent().getData();
// DEPRECATED
Cursor cursor = managedQuery(uri, null, null, null, null);
// WORKING - loadInBackground() preventing freezing of app
Cursor cursor = new CursorLoader(getApplicationContext(),uri, null, null, null, null).loadInBackground();
Update TextView from TimerTask, Handler, schedule, run, cancel TimerTask, Android example
public class TimerActivity extends Activity {
TimerTask mTimerTask;
final Handler handler = new Handler();
Timer t = new Timer();
TextView hTextView;
TableRow hTableRow;
Button hButton, hButtonStop;
private int nCounter = 0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
hTextView = (TextView)findViewById(R.id.idTextView);
hButton = (Button)findViewById(R.id.idButton);
hButton.setOnClickListener(mButtonStartListener);
hButtonStop = (Button)findViewById(R.id.idButtonStop);
hButtonStop.setOnClickListener(mButtonStopListener);
} // end onCreate
View.OnClickListener mButtonStartListener = new OnClickListener() {
public void onClick(View v) {
doTimerTask();
}
};
View.OnClickListener mButtonStopListener = new OnClickListener() {
public void onClick(View v) {
stopTask();
}
};
public void doTimerTask(){
mTimerTask = new TimerTask() {
public void run() {
handler.post(new Runnable() {
public void run() {
nCounter++;
// update TextView
hTextView.setText("Timer: " + nCounter);
Log.d("TIMER", "TimerTask run");
}
});
}};
// public void schedule (TimerTask task, long delay, long period)
t.schedule(mTimerTask, 500, 3000); //
}
public void stopTask(){
if(mTimerTask!=null){
hTextView.setText("Timer canceled: " + nCounter);
Log.d("TIMER", "timer canceled");
mTimerTask.cancel();
}
}
}
Editace: 2013-12-09 11:06:19
Počet článků v kategorii: 397
Url:java-basic-rules
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