有一个类似的问题here，但答案似乎从来没有找到过。我已经尝试了干净，但仍然得到了ClassNotFoundException。
所以发生了什么，就像链接的问题一样，我在ArrayList<Player>中调用了add函数，它继续告诉我它找不到Player类，即使它在那里并且我已正确导入它（因为它可以使用该路径中的其他类。我将尝试发布尽可能多的代码。
au.thewebeditor.scoreboard.apps.AccessMySQL.java
package au.thewebeditor.scoreboard.apps;
import java.sql.*;
import au.thewebeditor.scoreboard.defs.*;
public class AccessMySQL {
private static Connection connection = null;
private static Statement statement = null;
private static PreparedStatement preparedStatement = null;
private static ResultSet resultSet = null;
public static void readData() throws SQLException, ClassNotFoundException {
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:mysql://HOSTNAME/socmedi2_rce?user=socmedi2_sam&password=abc123");
statement = connection.createStatement();
resultSet = statement.executeQuery("SELECT * FROM scores WHERE hasChanged > 0");
writeResultSet(resultSet);
//resetHasChanged();
} catch (SQLException exc) {
throw exc;
} finally {
close();
}
}
private static void writeResultSet(ResultSet resultSet) throws SQLException {
while (resultSet.next()) {
int id = resultSet.getInt("id");
String name = resultSet.getString("name");
int score = resultSet.getInt("score");
int lastScore = resultSet.getInt("lastScore");
if (lastScore == 0){
Scoreboard.addScore(id, name, score);
} else {
for (int i = 0; i < Scoreboard.getLength(); i++){
if (Scoreboard.getID(i) == id){
Scoreboard.updateScore(i, score);
}
}
}
}
Scoreboard.sortScoreboard();
}
private static void resetHasChanged() throws SQLException{
preparedStatement = connection.prepareStatement("UPDATE scoreboard.scores SET hasChanged = 0 WHERE hasChanged > 0");
preparedStatement.executeUpdate();
}
private static void close() {
try {
if (resultSet != null) {
resultSet.close();
}
if (statement != null) {
statement.close();
}
if (connection != null) {
connection.close();
}
} catch (Exception e) {
//DO NOTHING???
}
}
}
au.thewebeditor.scoreboard.apps.Scorboard.java
package au.thewebeditor.scoreboard.apps;
import java.awt.*;
import java.awt.geom.*;
import java.sql.SQLException;
import java.util.*;
import javax.swing.*;
import au.thewebeditor.scoreboard.defs.*;
public class Scoreboard extends JWindow {
static Config configuration = new Config();
private static ArrayList<Player> scores = new ArrayList<Player>(20);
private static JLabel titleLabel = new JLabel();
private static JLabel subtitleLabel = new JLabel();
private static JLabel[] positionLabel = new JLabel[configuration.getListLength()];
private static JLabel[] nameLabel = new JLabel[configuration.getListLength()];
private static JLabel[] scoreLabel = new JLabel[configuration.getListLength()];
private static JLabel[] changeLabel = new JLabel[configuration.getListLength()];
private static JLabel[] arrowLabel = new JLabel[configuration.getListLength()];
public Scoreboard(){
//Set to full screen
this.setBounds(0, 0, Toolkit.getDefaultToolkit().getScreenSize().width, Toolkit.getDefaultToolkit().getScreenSize().height);
updateLabels(); //Set value of headings
updateScores();
this.getContentPane().setBackground(Color.white);
GridBagLayout mainLayout = new GridBagLayout();
setLayout(mainLayout);//Grid size is 5 across: Position, name, $value, change, arrow
//TITLE LABEL
GridBagConstraints constraint = AutoConstraint.buildConstraint(new AutoConstraint(0, 0, 5, 1, 100, 0, GridBagConstraints.CENTER));
mainLayout.setConstraints(titleLabel, constraint);
add(titleLabel);
//SUBTITLE LABEL
constraint = AutoConstraint.buildConstraint(new AutoConstraint(0, 1, 5, 1, 100, 0, GridBagConstraints.CENTER));
mainLayout.setConstraints(subtitleLabel, constraint);
add(subtitleLabel);
//SCOREBOARD
for (int i = 0; i < configuration.getListLength(); i++){
if (nameLabel[i].getText() == ""){
//Print empty line
constraint = AutoConstraint.buildConstraint(new AutoConstraint(1, i + 2, 5, 1, 100, 1, GridBagConstraints.WEST));
mainLayout.setConstraints(nameLabel[i], constraint);
add(nameLabel[i]);
} else {
add(arrowLabel[i]);
//ChangeLabel
constraint = AutoConstraint.buildConstraint(new AutoConstraint(0, i + 2, 1, 1, 20, 1, GridBagConstraints.EAST));
mainLayout.setConstraints(changeLabel[i], constraint);
add(changeLabel[i]);
//ArrowLabel
constraint = AutoConstraint.buildConstraint(new AutoConstraint(1, i + 2, 1, 1, 5, 1, GridBagConstraints.WEST));
mainLayout.setConstraints(arrowLabel[i], constraint);
add(arrowLabel[i]);
//PositionLabel
constraint = AutoConstraint.buildConstraint(new AutoConstraint(2, i + 2, 1, 1, 5, 1, GridBagConstraints.EAST));
mainLayout.setConstraints(positionLabel[i], constraint);
add(positionLabel[i]);
//NameLabel
constraint = AutoConstraint.buildConstraint(new AutoConstraint(3, i + 2, 1, 1, 40, 1, GridBagConstraints.WEST));
mainLayout.setConstraints(nameLabel[i], constraint);
add(nameLabel[i]);
//ScoreLabel
constraint = AutoConstraint.buildConstraint(new AutoConstraint(4, i + 2, 1, 1, 30, 1, GridBagConstraints.WEST));
mainLayout.setConstraints(scoreLabel[i], constraint);
add(scoreLabel[i]);
}
}
this.setBounds(0, 0, Toolkit.getDefaultToolkit().getScreenSize().width, Toolkit.getDefaultToolkit().getScreenSize().height);
setVisible(true);
}
public static void updateLabels() {//Updates heading labels
titleLabel.setText(configuration.getTitle());
subtitleLabel.setText(configuration.getSubtitle());
titleLabel.setFont(new Font("Segoe UI", Font.BOLD, (int)(42*configuration.getFontAdjust())));
subtitleLabel.setFont(new Font("Segoe UI", Font.BOLD, (int)(32*configuration.getFontAdjust())));
}
public static void updateScores() {//Updates scoreboard labels
try {
AccessMySQL.readData();
} catch (SQLException e) {
String[] options = {"Retry", "Exit"};
int response = JOptionPane.showOptionDialog(null, "MySQL database failed to load. Error code: " + Integer.toString(e.getErrorCode()) + ".\n" + e.getMessage(), "MySQL Error", 0, JOptionPane.ERROR_MESSAGE, null, options, options[1]);
if (response == 1 || response == JOptionPane.CLOSED_OPTION)
Runtime.getRuntime().exit(ERROR);
else
Program.redrawScoreboard();
} catch (ClassNotFoundException e) {
JOptionPane.showMessageDialog(null, "Hard Coded Failure, Contact Mowgli for Support.", "Error", JOptionPane.ERROR_MESSAGE);
Runtime.getRuntime().exit(ERROR);
}
int change = 0;
for (int i = 0; i < configuration.getListLength(); i++){
try {
positionLabel[i] = new JLabel(Integer.toString(i + 1) + ". ");
positionLabel[i].setFont(new Font("Segoe UI", Font.PLAIN, (int)(24*configuration.getFontAdjust())));
nameLabel[i] = new JLabel(scores.get(i).getName());
nameLabel[i].setFont(new Font("Segoe UI", Font.BOLD, (int)(24*configuration.getFontAdjust())));
scoreLabel[i] = new JLabel("$" + Integer.toString(scores.get(i).getScore()));
scoreLabel[i].setFont(new Font("Segoe UI", Font.PLAIN, (int)(24*configuration.getFontAdjust())));
change = scores.get(i).getLastPosition() - i - 1;
changeLabel[i] = new JLabel();
changeLabel[i].setFont(new Font("Segoe UI", Font.BOLD, (int)(24*configuration.getFontAdjust())));
if (scores.get(i).getLastPosition() == 0){
changeLabel[i].setText("NEW! ");
changeLabel[i].setForeground(Color.yellow);
arrowLabel[i] = new JLabel(" " + Character.toString((char)171));
arrowLabel[i].setForeground(Color.yellow);
} else if (change > 0){
changeLabel[i].setText("+" + Integer.toString(change) + " ");
changeLabel[i].setForeground(Color.green);
arrowLabel[i] = new JLabel(" " + Character.toString((char)233));
arrowLabel[i].setForeground(Color.green);
} else if (change < 0){
changeLabel[i].setText(Integer.toString(change) + " ");
changeLabel[i].setForeground(Color.red);
arrowLabel[i] = new JLabel(" " + Character.toString((char)234));
arrowLabel[i].setForeground(Color.red);
} else {
changeLabel[i].setText(Character.toString((char)177)+"0 ");
changeLabel[i].setForeground(Color.gray);
arrowLabel[i] = new JLabel(" " + Character.toString((char)108));
arrowLabel[i].setForeground(Color.gray);
}
scores.get(i).setLastPosition(i+1); //Sets last position before sort is called.
arrowLabel[i].setFont(new Font("Wingdings", Font.PLAIN, (int)(24*configuration.getFontAdjust())));
} catch (IndexOutOfBoundsException e) {
nameLabel[i] = new JLabel("");
}
}
}
public static void addScore(int id, String name, int score){//Adds new score to scores ArrayList
scores.add(new Player(id, name, score, 0));
}
public static void updateScore(int index, int score){//Updates score value, does not rearrange or assign lastPosition or position
scores.get(index).setScore(score);
}
public static int getLength(){//Returns the current length of the scoreboard
return scores.size();
}
public static int getID(int index){//takes the ArrayList index value and returns the ID value
return scores.get(index).getID();
}
public static void sortScoreboard(){//Sorts scoreboard DESC
Collections.sort(scores);
}
}
au.thewebeditor.scoreboard.apps.Program.java
package au.thewebeditor.scoreboard.apps;
public class Program {
private static Scoreboard sb;
private static ConfigPanel cp;
public Program(){
sb = new Scoreboard();
cp = new ConfigPanel();
}
public static void redrawScoreboard() throws NullPointerException{
try{
sb.dispose();
} catch (NullPointerException e){
//DO NOTHING
}
sb = new Scoreboard();
cp.toFront();
}
public static void showConfig(){
cp.setVisible(true);
cp.toFront();
}
public static void main(String[] arguments){
new Program();
}
}
我希望这足以发现错误信息。任何帮助将不胜感激。包括正确的编码习惯，因为我是Java新手。
答案 0 :(得分：0)
您使用Eclipse。这有点模糊，但从我们所知道的建议来看： 在Project Explorer中右键单击项目，然后单击Properties（上下文菜单的底部）。在即将出现的Properties对话框的左侧树视图中选择“Java Build Path”，这是你的朋友。您可以看到包含哪些库，库和项目依赖项是什么。您可以设置导出和导入的顺序，检查包含的来源等等。
您还可以在“属性”对话框中检查“Java编译器”树节点。您可以查看和更改Java兼容级别，JDK为您提供JVM，其他设置也很重要。
主要原因可能是未找到的类不在类路径中。由于它来自您自己的源代码，请检查我在（“源”选项卡）上引导您的对话框中包含的源文件夹。
检查您的项目是否具有所需的布局，包已到位。这是您从其他地方导入的项目吗？