Related
This is a service running in the background, no Activity, began operating normally, but After about four hours, there will be a ConnectTimeoutException.
Connect to xxx.xxx.xxx.xxx time out.
This problem occurs in Android 6, I did not find this issue Android 4. When this problem occurs, I have to restart this phone, after which it connects properly for some time. When this problem occurs, other network applications on the phone runs properly.
public class mService extends Service{
Intent intent;
private Handler objHandlerCheckNetwork = new Handler();
private boolean mReflectFlg = false;
private static final int NOTIFICATION_ID = 101;
private static final Class<?>[] mSetForegroundSignature = new Class[] { boolean.class };
private static final Class<?>[] mStartForegroundSignature = new Class[] { int.class , Notification.class };
private static final Class<?>[] mStopForegroundSignature = new Class[] { boolean.class };
private NotificationManager mNM;
private Method mSetForeground;
private Method mStartForeground;
private Method mStopForeground;
private Object[] mSetForegroundArgs = new Object[1];
private Object[] mStartForegroundArgs = new Object[2];
private Object[] mStopForegroundArgs = new Object[1];
private Runnable mHttpTestRunnable = new Runnable() {
#Override
public void run() {
if (httpTest()){
Log.e(GlobalData.getClassMethodName(),"true");
}else{
Log.e(GlobalData.getClassMethodName(),"false");
}
}
};
private Runnable mTasksCheckNetwork = new Runnable()
{
public void run()
{
Thread httpTestThread = new Thread(mHttpTestRunnable);;
httpTestThread.start();
objHandlerCheckNetwork.postDelayed(mTasksCheckNetwork, 1000*30);
}
};
#SuppressLint("NewApi")
#Override
public void onCreate() {
super.onCreate();
mNM = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE );
try {
mStartForeground = mService.class.getMethod("startForeground" , mStartForegroundSignature);
mStopForeground = mService.class.getMethod("stopForeground" , mStopForegroundSignature);
} catch (NoSuchMethodException e) {
mStartForeground = mStopForeground = null;
}
try {
mSetForeground = getClass().getMethod( "setForeground", mSetForegroundSignature);
} catch (NoSuchMethodException e) {
throw new IllegalStateException( "OS doesn't have Service.startForeground OR Service.setForeground!");
}
Intent intent = new Intent(this,UploadTableDataService.class );
intent.putExtra( "ficationId", NOTIFICATION_ID);
Notification.Builder builder = new Notification.Builder(this);
PendingIntent contentIntent = PendingIntent.getActivity(this, 0, intent, 0);
builder.setContentIntent(contentIntent);
builder.setSmallIcon(R.drawable.gps);
builder.setContentTitle( "test" );
builder.setContentText( "test111" );
Notification notification = builder.getNotification();
startForegroundCompat( NOTIFICATION_ID, notification);
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
super.onStartCommand(intent, flags, startId);
//startService( new Intent( this, WifiService. class));
//startService( new Intent( this, VoiceService. class));
this.intent = intent;
Log.e(GlobalData.getClassMethodName(),"mService start!");
objHandlerCheckNetwork.postDelayed(mTasksCheckNetwork, 1000);
return START_STICKY;
}
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public void onDestroy() {
super.onDestroy();
try{
objHandlerCheckNetwork.removeCallbacks(mTasksCheckNetwork);
}catch (Exception e) {
Log.d("DEBUG->", "onDestroy error - removeUpdates: ");
}
//stopForegroundCompat( NOTIFICATION_ID);
}
void invokeMethod(Method method, Object[] args) {
try {
method.invoke( this, args);
} catch (InvocationTargetException e) {
// Should not happen.
Log. w("ApiDemos" , "Unable to invoke method" , e);
} catch (IllegalAccessException e) {
// Should not happen.
Log. w("ApiDemos" , "Unable to invoke method" , e);
}
}
/**
* This is a wrapper around the new startForeground method, using the older
* APIs if it is not available.
*/
void startForegroundCompat( int id, Notification notification) {
if ( mReflectFlg) {
// If we have the new startForeground API, then use it.
if ( mStartForeground != null) {
mStartForegroundArgs[0] = Integer. valueOf(id);
mStartForegroundArgs[1] = notification;
invokeMethod( mStartForeground, mStartForegroundArgs);
return;
}
// Fall back on the old API.
mSetForegroundArgs[0] = Boolean. TRUE;
invokeMethod( mSetForeground, mSetForegroundArgs);
mNM.notify(id, notification);
} else {
if (Build.VERSION. SDK_INT >= 5) {
startForeground(id, notification);
} else {
// Fall back on the old API.
mSetForegroundArgs[0] = Boolean. TRUE;
invokeMethod( mSetForeground, mSetForegroundArgs);
mNM.notify(id, notification);
}
}
}
/**
* This is a wrapper around the new stopForeground method, using the older
* APIs if it is not available.
*/
void stopForegroundCompat( int id) {
if ( mReflectFlg) {
// If we have the new stopForeground API, then use it.
if ( mStopForeground != null) {
mStopForegroundArgs[0] = Boolean. TRUE;
invokeMethod( mStopForeground, mStopForegroundArgs);
return;
}
mNM.cancel(id);
mSetForegroundArgs[0] = Boolean. FALSE;
invokeMethod( mSetForeground, mSetForegroundArgs);
} else {
if (Build.VERSION. SDK_INT >= 5) {
stopForeground( true);
} else {
// Fall back on the old API. Note to cancel BEFORE changing the
// foreground state, since we could be killed at that point.
mNM.cancel(id);
mSetForegroundArgs[0] = Boolean. FALSE;
invokeMethod( mSetForeground, mSetForegroundArgs);
}
}
}
public static Boolean httpTest() {
HttpClient client= new DefaultHttpClient();;
try {
StringBuilder sb = new StringBuilder();
HttpParams httpParams = client.getParams();
HttpConnectionParams.setConnectionTimeout(httpParams, 1000*5);
HttpConnectionParams.setSoTimeout(httpParams, 1000*10);
HttpResponse response = client.execute(new HttpGet("http://www.itnanny.com/default.htm"));
HttpEntity entity = response.getEntity();
if (entity != null) {
BufferedReader reader = new BufferedReader(new InputStreamReader(entity.getContent(), "UTF-8"), 8192);
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
reader.close();
}
Log.e(GlobalData.getClassMethodName(),"result："+sb.toString());
if (sb.toString().indexOf("ok") > -1){
return true;
}
} catch (Exception e) {
e.printStackTrace();
}finally {
client.getConnectionManager().shutdown();;
}
return false;
}
}
I write online game. For game logic, I need select random users(etc) from database. How to achive this with java api? What the most perfomance way to do this?
I can use something like(pseudocode): select from User skip(randomNum(0,usersCount)) limit 1 but how write in documentation - skip has bad performance.
I have tried with this code
int numberRandom= 5;
String string="[";
int cluster= db.getMetadata().getSchema().getClass("User").getClusterIds()[0];
for(int i=0;i<numberRandom;i++){
int random=ThreadLocalRandom.current().nextInt(0, 96000);
if(i==(numberRandom-1))
string += cluster+":"+random + "]";
else
string += cluster+":"+random + ",";
}
Iterable<Vertex> result = g.command(new OCommandSQL("select from "+ string)).execute();
for(Vertex v:result)
System.out.println(v.getId());
Let me know if it can be a good solution for you
I wrote two java classes, both are getting X random users from a specific cluster.
The first one seams faster to me. (about 0.8s vs 1.2s)
testRandom.java
public class testRandom {
public static void main(String[] args) {
// TODO Auto-generated method stub
String nomeDb = "RandomUser";
try {
OServerAdmin serverAdmin = new OServerAdmin("remote:localhost/"+nomeDb).connect("root", "root");
if(serverAdmin.existsDatabase()){ // il db esiste
//connessione a db
OrientGraph g = new OrientGraph("remote:localhost/"+nomeDb);
//------------------------------------------------
long Tbegin,Tend;
float millis;
Tbegin = System.currentTimeMillis();
int numberRandom= 5;
int random;
String cluster = "user";
Iterable<Vertex> vertices = g.command(new OCommandSQL("select from cluster:"+cluster)).execute();
List<Vertex> v_array = new ArrayList<Vertex>();
List<Vertex> res = new ArrayList<Vertex>();
for(Vertex v : vertices){
v_array.add(v);
}
int arraysize = v_array.size();
for(int i=0;i<numberRandom;i++){
random=ThreadLocalRandom.current().nextInt(0, arraysize);
res.add(v_array.get(random));
}
for(Vertex v : res){
System.out.println(v.getId());
}
Tend = System.currentTimeMillis();
millis = (Tend-Tbegin);
System.out.println("--Execution time: "+millis/1000+ "s\n");
//------------------------------------------------
//chiude db
g.shutdown();
}
else{
System.out.println("Il database '"+ nomeDb + "' non esiste");
}
serverAdmin.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
testRandomSkip.java
public class testRandom_skip {
public static void main(String[] args) {
// TODO Auto-generated method stub
String nomeDb = "RandomUser";
try {
OServerAdmin serverAdmin = new OServerAdmin("remote:localhost/"+nomeDb).connect("root", "root");
if(serverAdmin.existsDatabase()){ // il db esiste
//connessione a db
OrientGraph g = new OrientGraph("remote:localhost/"+nomeDb);
//------------------------------------------------
long Tbegin,Tend;
float millis;
Tbegin = System.currentTimeMillis();
int numberRandom= 5;
int random;
String cluster = "user";
List<Vertex> res = new ArrayList<Vertex>();
Iterable<Vertex> q_count_V = g.command(new OCommandSQL("select count(*) from cluster:"+cluster)).execute();
Long count_V = 0l;
for(Vertex v : q_count_V){
count_V=v.getProperty("count");
break;
}
for(int i=0;i<numberRandom;i++){
random=(int)ThreadLocalRandom.current().nextLong(0, count_V);
Iterable<Vertex> vertex = g.command(new OCommandSQL("select from cluster:"+cluster+" skip "+random+" limit 1")).execute();
for(Vertex v : vertex){
res.add(v);
break;
}
}
for(Vertex v : res){
System.out.println(v.getId());
}
Tend = System.currentTimeMillis();
millis = (Tend-Tbegin);
System.out.println("--Execution time: "+millis/1000+ "s\n");
//------------------------------------------------
//chiude db
g.shutdown();
}
else{
System.out.println("Il database '"+ nomeDb + "' non esiste");
}
serverAdmin.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
Hope it helps.
Ivan
public class Server {
public static Maze lab;
public static Socket s;
public static Socket z;
public static player human;
public static BufferedReader input;
public static OutputStream os;
public static InputStream is;
public static int n=-1;
public static connections info;
public static ObjectOutputStream oos;
public static void main(String[] args) {
try{
ServerSocket Serversocket = new ServerSocket(1900);
System.out.println("Maze Game Server Started on port " + Serversocket.getLocalPort());
FileInputStream fis = new FileInputStream("labirintas.cfg");
ObjectInputStream ois = new ObjectInputStream(fis);
lab = (Maze) ois.readObject();
fis.close();
ois.close();
info = new connections();
try {
while(true){
try{
s = Serversocket.accept();
z = Serversocket.accept();
System.out.println("Conection from: " + s.getLocalAddress().getHostAddress());
os = s.getOutputStream();
is = z.getInputStream();
oos = new ObjectOutputStream(os);
oos.writeObject(lab);
oos.flush();
n++;
//is.close();
human = new player(n);
human.start();
}catch(Exception exception){
System.out.println("nėra labirinto" + exception.getMessage());
System.exit(0);
}finally
{
s.close();
}
}
} catch ( Exception ex) {
System.out.println(ex.getMessage());
}
}catch(Exception e){
System.out.println(e.getMessage());
}
}
public static class player extends Thread{
public int x=0;
public int y=0;
public int counter = 0;
public String nick="";
public player(int n){
x=0;
y=0;
counter = n;
try{
input = new BufferedReader(new InputStreamReader(is));
nick = input.readLine();
System.out.println(counter+" "+x+" "+y+" "+ nick );
info.info(counter, x, y, nick);
oos.writeObject(info);
oos.flush();
}catch(Exception e){
System.out.println(e.getStackTrace());
}
}
public int getcooX(){
return x;
}
public int getcooY(){
return y;
}
public void moveUP(){
x--;
}
public void moveDOWN(){
x++;
}
public void moveLEFT(){
y--;
}
public void moveRIGHT(){
y++;
}
#Override
public void run(){
try{
while(true){
System.out.println(s + " with name: "+ nick + ": " + (s.isConnected()?"true":"false"));
if (input!=null){
String command = input.readLine();
System.out.println(command);
if(command.startsWith("MOVE_UP")){
System.out.println("up move");
if (lab.checkUP(x, y)==false){
System.out.println("up accepted");
x--;
info.info(counter, x, y, nick);
oos.writeObject(info);
oos.flush();
}
if(lab.isItWin(x, y)){
System.out.println("Winner");
s.close();
}
}
else if(command.startsWith("MOVE_LEFT")){
System.out.println("left move");
if (lab.checkLEFT(x, y)==false){
System.out.println("left accepted");
y--;
info.info(counter, x, y, nick);
oos.writeObject(info);
oos.flush();
}
if(lab.isItWin(x, y)){
System.out.println("Winner");
s.close();
}
}
else if(command.startsWith("MOVE_RIGHT")){
System.out.println("right move");
if (lab.checkRIGHT(x, y)==false){
System.out.println("right accepted");
y++;
info.info(counter, x, y, nick);
oos.writeObject(info);
oos.flush();
}
if(lab.isItWin(x, y)){
System.out.println("Winner");
s.close();
}
}
else if(command.startsWith("MOVE_DOWN")){
System.out.println("down move");
if (lab.checkRIGHT(x, y)==false){
System.out.println("down accepted");
y++;
info.info(counter, x, y, nick);
oos.writeObject(info);
oos.flush();
}
if(lab.isItWin(x, y)){
System.out.println("Winner");
s.close();
}
}
}
}
}catch(Exception e){
System.out.println(e.getMessage());
}
}
}
}
Why do I get java.lang.NullPointerException? I think I'm doing everything right. I don't understand why I get this.
here the client, and the connections classes.
public class Client implements ActionListener, Serializable{
public static JFrame main;
public static JPanel mainP;
public static JLabel text;
public static JButton New;
public static JButton exit;
public static JTextField nickas;
public JPanel labirintas;
public JMenuBar bar;
public JMenu file;
public JMenu edit;
public JMenuItem close;
public JFrame kurti;
public JLabel[][] label;
public JFrame zaidimas;
public static Maze lab;
public Color sienos = Color.BLACK;
public Color zaidejo = Color.RED;
public Color laimejimo = Color.GREEN;
public Color laukeliai = Color.WHITE;
public int cooX = 0;
public int cooY = 0;
public static PrintWriter output;
public static Socket s;
public static Socket f;
public static connections info;
public static InputStream os;
public static ObjectInputStream oos;
public static void main(String[] args) {
main = new JFrame("Pagrindinis meniu");
main.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
mainP = new JPanel();
text = new JLabel("Sveiki čia labirinto žaidimas. Įveskite savo vardą. Pasirinkite ką"
+ " darysite", SwingConstants.CENTER);
text.setVerticalAlignment(SwingConstants.TOP);
New = new JButton("Pradėti žaidimą");
nickas = new JTextField();
nickas.setDocument(new JTextFieldLimit(10));
mainP.setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
c.fill = GridBagConstraints.HORIZONTAL;
c.gridx = 0;
c.gridy = 0;
c.insets = new Insets(10,0,0,0);
mainP.add(text, c);
c.gridx=0;
c.gridy = 1;
mainP.add(nickas, c);
c.gridx = 0;
c.gridy = 2;
mainP.add(New, c);
exit = new JButton("Išeiti iš žaidimo");
c.gridx = 0;
c.gridy = 3;
mainP.add(exit, c);
main.add(mainP);
main.setSize(500, 500);
main.show();
New.addActionListener(new Client());
exit.addActionListener(new Client());
}
#Override
public void actionPerformed(ActionEvent e){
Object source =e.getActionCommand();
if (source.equals("Pradėti žaidimą")){
String nick = nickas.getText();
try{
if(nick.isEmpty()){
JOptionPane.showMessageDialog(main, "Enter Your name", "Please Enter Your name", JOptionPane.ERROR_MESSAGE);
}
else{
s = new Socket("localhost",1900);
f = new Socket("localhost",1900);
os = s.getInputStream();
oos = new ObjectInputStream(os);
lab = (Maze) oos.readObject();
OutputStream is = f.getOutputStream();
//os.close();
output = new PrintWriter(is, true);
main.show(false);
zaidimas =new JFrame("Labirinto kurimas");//sukuriu nauja frame labirinto zaidimui
zaidimas.setLayout(new GridBagLayout());
zaidimas.setBackground(Color.BLACK);
GridBagConstraints ck = new GridBagConstraints(); //sukuriu nauja GridBagConstraints stiliui kurti
/////////////////////
zaidimas.setSize(1200, 600);
bar = new JMenuBar();//meniu juosta
file = new JMenu("File");
edit = new JMenu("Edit");
/////////////////////
bar.add(file);
bar.add(edit);
file.add(close = new JMenuItem("Close"));
close.setAccelerator(KeyStroke.getKeyStroke('C', Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
//////////////////
JMenuItem spalvos = new JMenuItem("Spalvų meniu");
edit.add(spalvos);
spalvos.setAccelerator(KeyStroke.getKeyStroke('P', Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
/////////////////
ck.gridx = 0;//pridedu ja i tokias koordinates
ck.gridy = 0;
ck.fill = GridBagConstraints.HORIZONTAL;//issitemptu horizontaliai
ck.anchor = GridBagConstraints.NORTHWEST;
ck.gridwidth = 4;
ck.weightx = 1.0;
ck.weighty = 0.0;
zaidimas.add(bar, ck);
/////////////////////
labirintas = new JPanel();//labirinto panele
labirintas.setLayout(new GridLayout(lab.h,lab.v));
ck.gridy = 1;
ck.weightx = 0.8;
ck.weighty = 1.0;
ck.fill = GridBagConstraints.BOTH;
zaidimas.add(labirintas, ck);
/////////////////////
text = new JLabel("Online:");
ck.gridx = 4;
ck.weightx = 0.2;
ck.weighty=1.0;
ck.fill = GridBagConstraints.BOTH;
ck.anchor = GridBagConstraints.FIRST_LINE_START;
zaidimas.add(text, ck);
////////
label = new JLabel[lab.h][lab.v];//sukuriu masyva labeliu
////////////////
sienos();
///////////////
label[0][0].setBackground(zaidejo);
///////////////
try{
output.println(nick);
online();
}catch(Exception b){
}
zaidimas.addKeyListener(new KeyListener(){
#Override
public void keyReleased(KeyEvent K){
try{
if (K.getKeyCode()==KeyEvent.VK_A){
output.println("MOVE_LEFT");
output.flush();
if (lab.checkLEFT(cooX, cooY)==false){
label[cooX][cooY].setBackground(Color.white);
cooY--;
online();
}
if(lab.isItWin(cooX, cooY)){
JOptionPane.showMessageDialog(main, "Winner!", "You Won.", JOptionPane.PLAIN_MESSAGE);
System.out.println("Winner");
s.close();
f.close();
System.exit(0);
}
}
else if (K.getKeyCode()==KeyEvent.VK_W){
output.println("MOVE_UP");
output.flush();
if (lab.checkUP(cooX, cooY)==false){
label[cooX][cooY].setBackground(Color.white);
cooX--;
online();
}
if(lab.isItWin(cooX, cooY)){
JOptionPane.showMessageDialog(main, "Winner!", "You Won.", JOptionPane.PLAIN_MESSAGE);
System.out.println("Winner");
s.close();
f.close();
System.exit(0);
}
}
else if (K.getKeyCode()==KeyEvent.VK_D){
output.println("MOVE_RIGHT");
output.flush();
if (lab.checkRIGHT(cooX, cooY)==false){
label[cooX][cooY].setBackground(Color.white);
cooY++;
online();
}
if(lab.isItWin(cooX, cooY)){
JOptionPane.showMessageDialog(main, "Winner!", "You Won.", JOptionPane.PLAIN_MESSAGE);
System.out.println("Winner");
s.close();
f.close();
System.exit(0);
}
}
if (K.getKeyCode()==KeyEvent.VK_S){
output.println("MOVE_DOWN");
output.flush();
if (lab.checkDOWN(cooX, cooY)==false){
label[cooX][cooY].setBackground(Color.white);
cooX++;
online();
}
if(lab.isItWin(cooX, cooY)){
JOptionPane.showMessageDialog(main, "Winner!", "You Won.", JOptionPane.PLAIN_MESSAGE);
System.out.println("Winner");
s.close();
f.close();
System.exit(0);
}
}
}catch(Exception ex){
}
}
public void keyPressed(KeyEvent key){}
public void keyTyped(KeyEvent keyE){}
});
///////////////
zaidimas.show();
close.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
zaidimas.dispose();
main.dispose();
System.exit(0);
}
});
zaidimas.addWindowListener(new WindowAdapter(){
#Override
public void windowClosing(WindowEvent wind){
main.show(true);
mainP.show(true);
try{
s.close();
f.close();
}catch(Exception ex){
}
}
});
}
}catch(UnknownHostException exception){
JOptionPane.showMessageDialog(main, exception.getMessage()+exception, "Host error", JOptionPane.ERROR_MESSAGE);
exception.getStackTrace();
}
catch(Exception except){
JOptionPane.showMessageDialog(main, except.getMessage()+except, "Fatal error", JOptionPane.ERROR_MESSAGE);
except.getStackTrace();
}
}
else if (source.equals("Išeiti iš žaidimo")){
main.dispose();
System.exit(0);
}
}
// public void gamer(){//tikrina ar zaidejas yra laimejimo langelija
// label[game.getcooX()][game.getcooY()].setBackground(zaidejo);
// if (lab.isItWin(game.getcooX(), game.getcooY())){
// zaidimas.dispose();
// JOptionPane.showMessageDialog(main, "Jūs laimėjote!", "Sveikiname", JOptionPane.ERROR_MESSAGE);
// main.show(true);
// mainP.show(true);
// }
// }
public void sienos(){
for(int i=0;i<lab.h;i++){
for(int j=0; j<lab.v;j++){//ciklas braizyti sienom
label[i][j] = new JLabel();
int t=0,r=0,bot=0,l = 0;//i sias reiksmes isirasysiu sienu ploti
if (i==0){
if(lab.checkUP(i, j)) t=5; //tikrina ar borderis, jei borderis, tai storesne siena, jei ne, tai plonesne
}
else {
if(lab.checkUP(i, j)) t=2;
}
if (i==lab.h-1){
if(lab.checkDOWN(i, j)) bot=5;
}
else{
if(lab.checkDOWN(i, j)) bot=2;
}
if(j==lab.v-1){
if(lab.checkRIGHT(i, j)) r=5;
}
else{
if(lab.checkRIGHT(i, j)) r=2;
}
if (j==0){
if(lab.checkLEFT(i, j)) l=5;
}
else{
if(lab.checkLEFT(i, j)) l=2;
}
label[i][j].setBorder(BorderFactory.createMatteBorder(t, l, bot,r , sienos));
label[i][j].setOpaque(true); //kad matytusi labelis
if(lab.isItWin(i, j)) label[i][j].setBackground(laimejimo);
else label[i][j].setBackground(laukeliai);
labirintas.add(label[i][j]);
}
}
}
public void online(){
try{
info = (connections) oos.readObject();
}catch(Exception e){
System.out.println(e.getCause());}
text.setText("Online:");
for (int i=0;i<info.names.length;i++){
text.setText(text.getText() + "\n" + info.names[i]);
label[info.x[i]][info.y[i]].setBackground(Color.gray);
if(lab.isItWin(info.x[i], info.y[i])) label[info.x[i]][info.y[i]].setBackground(laimejimo);
label[cooX][cooX].setBackground(Color.white);
}
}
}
public class connections {
public String[] names;
public int[] x;
public int[] y;
public void connections(){
names = new String[99];
x = new int[99];
y = new int[99];
for (int i=0;i<100;i++){
names[i]="";
x[i]=0;
y[i]=0;
}
}
public void info(int n,int x,int y,String name){
names[n]=name;
this.x[n]=x;
this.y[n]=y;
}
}
Here's what I get from stacktrace:
java.lang.NullPointerException
at client.connections.info(connections.java:24)
at server.Server$player.<init>(Server.java:90)
at server.Server.main(Server.java:57)
The class connections does not have a constructor so the variable names never gets initialized. So when you call the method info and it tries to set names[n]=name it throws a NullPointerException because names is still null.
It looks like you have a constructor because you have a method named connections which is the same as the class name. However, you gave the method a return type of void which prevents it from being a constructor as constructors do not have a return type.
Change that line to:
public class connections {
public connections(){
...
You will now get a NullPointerException because you are attempting to set the 100th location of your names array in your constructor of the connections class.
You create the names array with length 99.
Then your for loop iterates through the numbers 0 through 99 (less than 100).
The problem is that the highest allowable index of names is 98 which is the 99th location. So when you try to set names[99] = "" it throws a NullPointerException.
Change your for loop to only go up to 99 instead of 100:
public connections(){
names = new String[99];
x = new int[99];
y = new int[99];
for (int i=0;i<99;i++){
names[i]="";
x[i]=0;
y[i]=0;
}
}
Or change the arrays to be length 100 to match the for loop:
public connections(){
names = new String[100];
x = new int[100];
y = new int[100];
for (int i=0;i<100;i++){
names[i]="";
x[i]=0;
y[i]=0;
}
}
Java Class Names
In Java the convention is to name all classes with mixed case with the first letter capitalized. See Java Naming Convention
Methods should be name with mixed case with the first letter lowercase.
You should change your connections class as follows:
public class Connections {
public Connections(){
...
I have a LWUIT app that should display the number of records in a LWUIT list.
To get all the records I use a method called getRecordData() that returns all records as a String array, it works fine.
But how do I count the number of these records?
import java.util.*;
import com.sun.lwuit.events.*;
import javax.microedition.midlet.*;
import com.sun.lwuit.*;
import com.sun.lwuit.plaf.*;
import javax.microedition.rms.RecordStore;
import javax.microedition.rms .*;
public class number_of_records extends MIDlet {
private RecordStore recordStore;
// Refresh2( ) method for getting the time now
public String Refresh2()
{
java.util.Calendar calendar = java.util.Calendar.getInstance();
Date myDate = new Date();
calendar.setTime(myDate);
StringBuffer time = new StringBuffer();
time.append(calendar.get(java.util.Calendar.HOUR_OF_DAY)).append(':');
time.append(calendar.get(java.util.Calendar.MINUTE)) ;
// time.append(calendar.get(java.util.Calendar.SECOND));
String tt = time.toString();
return tt;
}
// return all records of recordStore RecordStore
public String [] getRecordData( )
{
String[] str = null;
int counter = 0;
try
{
RecordEnumeration enumeration = recordStore.enumerateRecords(null, null, false);
str = new String[recordStore.getNumRecords()];
while(enumeration.hasNextElement())
{
try
{
str[counter] = (new String(enumeration.nextRecord()));
counter ++;
}
catch(javax.microedition.rms.RecordStoreException e)
{
}
}
}
catch(javax.microedition.rms.RecordStoreNotOpenException e)
{
}
catch(java.lang.NullPointerException n)
{
}
return str;
}
public void startApp()
{
com.sun.lwuit.Display.init(this);
final Button addition = new Button("add a goal");
final com.sun.lwuit.TextField tf = new com.sun.lwuit.TextField();
final com.sun.lwuit.List mylist = new com.sun.lwuit.List();
final Button All = new Button("All Goals");
final com.sun.lwuit.Form ff = new com.sun.lwuit.Form();
final com.sun.lwuit.Form g = new com.sun.lwuit.Form();
ff.getStyle().setBgColor(0X99CCFF);
All.getStyle().setBgColor(0X0066CC);
Style g_style5 = g.getSelectedStyle() ;
g.addComponent(tf);
g.addComponent(addition);
addition.getStyle().setBgColor(0X0066CC);
g.addComponent(All);
g.getStyle().setBgColor(0X99CCFF);
addition.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent ae)
{
//
String s =tf.getText();
if( s!=null && s.length() > 0)
{
try
{
// Store the time in the String k
String k = Refresh2();
// The record and the time stored in KK String
String kk =tf.getText()+"-"+k;
// Add an item (the kk String) to mylist List.
mylist.addItem(kk);
byte bytestream[] = kk.getBytes() ;
// Add a record to recordStore.
int i = recordStore.addRecord(bytestream, 0, bytestream.length);
}
catch(Exception ex) { }
// Inform the User that he added the a record.
Dialog validDialog = new Dialog(" ");
Style Dialogstyle = validDialog.getSelectedStyle() ;
validDialog.setScrollable(false);
validDialog.getDialogStyle().setBgColor(0x0066CC);
validDialog.setTimeout(1000); // set timeout milliseconds
TextArea textArea = new TextArea("...."); //pass the alert text here
textArea.setFocusable(false);
textArea.setText("A goal has been added"+"" );
validDialog.addComponent(textArea);
validDialog.show(0, 10, 10, 10, true);
}
// Information to user that he/she didn’t add a record
else if((s==null || s.length()<= 0))
{
Dialog validDialo = new Dialog(" ");
validDialo.setScrollable(false);
validDialo.getDialogStyle().setBgColor(0x0066CC);
validDialo.setTimeout(5000); // set timeout milliseconds
TextArea textArea = new TextArea("...."); //pass the alert text here
textArea.setFocusable(false);
textArea.setText("please enter scorer name or number");
validDialo.addComponent(textArea);
validDialo.show(50, 50, 50, 50, true);
}
}
});
/*Action here for displaying all records of recordStore RecordStore in a new form */
All.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
try
{
recordStore = RecordStore.openRecordStore("My Record Store", true);
}
catch(Exception ex) {}
try
{
com.sun.lwuit.Label l = new com.sun.lwuit.Label(" Team Goals") ;
ff.addComponent(l);
// Store the records of recordStore in string array
String [] record= getRecordData();
int j1;
String valueToBeInserted2="";
int k=getRecordData().length;
for( j1=0;j1< getRecordData().length;j1++)
{
valueToBeInserted2=valueToBeInserted2 + " " + record[j1];
if(j1==getRecordData().length)
{
mylist.addItem(record[j1]);
int m = getRecordData().length;
// Counting the number of records
String goals =""+getRecordData().length;
/* I tried to use for…loop to count them by length of the recordStore and render it.
This list also should display the number of records on the form.
But it didn’t !!!
*/
mylist.addItem(goals);
}
}
ff.addComponent(mylist);
}
catch(java.lang.IllegalArgumentException e)
{
}
finally
{
ff.show();
}
}
}
);
g.show();
}
public void pauseApp()
{
}
public void destroyApp(boolean unconditional) {
}
}
I Wrote this code but it gives NullPointerException at recordStore.enumerateRecords (null, null,true);
So I think the problem here.
please help.
myButton.addActionListener( new ActionListener()
{
public void actionPerformed(ActionEvet av)
{
try
{
RecordEnumeration enumeration = recordStore.enumerateRecords (null, null,true);
int o =recordStore.getNumRecords () ;
}
catch(Exception e)
{
}
}
});
what you need is enumeration.numRecords(); i reckon recordStore.getNumRecords() should work also, since this is what you are using the populate the array, you could even use the length of the array itself. These options are all in the code, it would be better to explore a bit more and also check the documentation to resolve trivial problems.
you could use the length of the array or set a RecordListener to your recordstore and increase a counter when added a record to recordstore.
here is the solution of my problem , I do a for loop to get the number of
elements of the array.
the counter should be the length of array
count.addActionListener( new ActionListener()
{
public void actionPerformed(ActionEvent av)
{
try
{
recordStore = RecordStore.openRecordStore("recordStore", true);
}
catch(Exception e)
{ }
try
{
RecordEnumeration enumeration = recordStore.enumerateRecords (null, null,true);
}
catch(Exception e)
{
}
String record[] = getRecordData();
int j;
j = record.length-1;
Dialog validDialog = new Dialog(" ");
Style Dialogstyle = validDialog.getSelectedStyle() ;
validDialog.setScrollable(false);
validDialog.getDialogStyle().setBgColor(0x0066CC);
validDialog.setTimeout(1000); // set timeout milliseconds
TextArea textArea = new TextArea("....");
textArea.setFocusable(false);
textArea.setText("Number Counted"+j );
validDialog.addComponent(textArea);
validDialog.show(0, 10, 10, 10, true);
}});
I am trying to move between 3 forms. 1 is main form and 2 other simple forms.
I have commands in the soft keys but they are not working...
below is my code...
public class checkOutComponents extends MIDlet implements ActionListener
{
private Form appForm;
private Form f1;
private Form f2;
Command GoTof1 = new Command("GoTof1");
Command GoTof2 = new Command("GoTof2");
Command GoToMainForm = new Command("GoToMainForm");
public void startApp()
{
Display.init(this);
appForm = new Form("Check These Components!! ");
appForm.setLayout(new BorderLayout());
appForm.addCommand(GoTof1);
appForm.addCommand(GoTof2);
appForm.addComponent(BorderLayout.CENTER, formContainer);
appForm.show();
}
public void pauseApp()
{
}
public void destroyApp(boolean unconditional)
{
}
public void actionPerformed(ActionEvent event)
{
Command eventCmd = event.getCommand();
Form f = Display.getInstance().getCurrent();
boolean sentido = false;
if (eventCmd == GoTof1)
{
sentido = true;
Image i1 = null;
try
{
i1 = Image.createImage("/hello/1.jpeg");
}
catch (IOException ex)
{
ex.printStackTrace();
}
Label lab1 = new Label(i1);
f1.addComponent(lab1);
f1.addCommand(GoTof2);
f1.addCommand(GoToMainForm);
f.setTransitionOutAnimator(Transition3D.createCube(300, sentido));
f1.show();
}
else if (eventCmd == GoTof2)
{
sentido = false;
Image i2 = null;
try
{
i2 = Image.createImage("/hello/2.jpeg");
}
catch (IOException ex)
{
ex.printStackTrace();
}
Label lab2 = new Label(i2);
f1.addComponent(lab2);
f1.addCommand(GoTof1);
f1.addCommand(GoToMainForm);
f.setTransitionOutAnimator(Transition3D.createCube(300, sentido));
f2.show();
}
else if(eventCmd == GoToMainForm)
{
appForm.showBack();
}
}
}
Kindly help regarding this.
Thanks in advance and regards,
Swati
Add command listener to the form appForm.
appForm.addCommandListener(this);