为什么我得到 null.pointer 异常，我确定哪里没有任何空变量
Why I get null.pointer exception, I am sure where aren't any null variables
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());
}
}
}
}
为什么我会得到 java.lang.NullPointerException？我认为我做的一切都是对的。我不明白为什么我得到这个。
这里是客户端，连接 类.
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;
}
}
这是我从堆栈跟踪中得到的：
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)
class connections 没有构造函数，因此变量 names 永远不会被初始化。因此，当您调用方法 info 并尝试设置 names[n]=name 时，它会抛出 NullPointerException，因为 names 仍然为空。
看起来你有一个构造函数，因为你有一个名为 connections 的方法，它与 class 名称相同。但是，您为该方法提供了 return 类型的 void ，这会阻止它成为构造函数，因为构造函数没有 return 类型。
将该行更改为：
public class connections {
public connections(){
...
您现在将得到 NullPointerException，因为您试图在 connections class.
的构造函数中设置 names 数组的第 100 个位置
您创建了长度为 99 的 names 数组。
然后您的 for 循环遍历数字 0 到 99（小于 100）。
问题是names的最高允许索引是98，也就是第99个位置。因此，当您尝试设置 names[99] = "" 时，它会抛出 NullPointerException。
将您的 for 循环更改为仅达到 99 而不是 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;
}
}
或者将数组的长度更改为 100 以匹配 for 循环：
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 姓名
在 Java 中，惯例是将所有 class 命名为混合大小写，首字母大写。参见 Java Naming Convention
方法名称应为大小写混合且首字母小写。
您应该按如下方式更改您的 connections class：
public class Connections {
public Connections(){
...
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());
}
}
}
}
为什么我会得到 java.lang.NullPointerException？我认为我做的一切都是对的。我不明白为什么我得到这个。 这里是客户端，连接 类.
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;
}
}
这是我从堆栈跟踪中得到的：
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)
class connections 没有构造函数，因此变量 names 永远不会被初始化。因此，当您调用方法 info 并尝试设置 names[n]=name 时，它会抛出 NullPointerException，因为 names 仍然为空。
看起来你有一个构造函数，因为你有一个名为 connections 的方法，它与 class 名称相同。但是，您为该方法提供了 return 类型的 void ，这会阻止它成为构造函数，因为构造函数没有 return 类型。
将该行更改为：
public class connections {
public connections(){
...
您现在将得到 NullPointerException，因为您试图在 connections class.
names 数组的第 100 个位置
您创建了长度为 99 的 names 数组。
然后您的 for 循环遍历数字 0 到 99（小于 100）。
问题是names的最高允许索引是98，也就是第99个位置。因此，当您尝试设置 names[99] = "" 时，它会抛出 NullPointerException。
将您的 for 循环更改为仅达到 99 而不是 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;
}
}
或者将数组的长度更改为 100 以匹配 for 循环：
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 姓名
在 Java 中，惯例是将所有 class 命名为混合大小写，首字母大写。参见 Java Naming Convention
方法名称应为大小写混合且首字母小写。
您应该按如下方式更改您的 connections class：
public class Connections {
public Connections(){
...