Java programming baseclass

CEHJ,
       The article you sent contains the informatin about the OOP concept.But, I am looking for a real  simple example that would have a base class and then derive the other objects from that class.If you could send me one, I would really appreicate it.Thanks for your help.

class A {
      public void foo() {
            System.out.println(getClass());
      }
}


class B extends A {
}

public class TestInheritance {
      public static void main(String[] args) {
            A a = new A();
            a.foo();
            B b = new B();
            b.foo();
      }
}

Save it as TestInheritance.java and compile and run it

>>abstract class TwoWheeler

Not really a good candidate for an abstract class (and some others) - but let's keep it simple for now ...

Now I am getting a picture whne exactly a base class is required. I am looking at a base class below and it does have a core class associated to it. Can you please have a look both the classes and let me know why would some one need a core class with similar functionality. Both classes are seperated by '***********'.Thanks for your help.

AppBase class ...................


package com.transport;

import java.io.PrintStream;
import java.text.DateFormat;
import com.transport.log.EventLog;
import com.transport.log.StatusLog;
import com.transport.log.Log;
import com.transport.remote.CommServer;
import com.transport.launch.SystemServerApp;
import com.transport.scheduler.Scheduler;
import com.transport.error.ErrHandler;



public class AppBase implements Debuger, Folderable {
      public final static String NL = System.getProperty("line.separator");
      public final static String FS = System.getProperty("file.separator");
      public final static String programConfigName = "program.cfg";      
      public final static String NONE = "None";
      public final static String SYSTEM_WORD = "SYSTEM_DEFAULT";
      public final static String DEFAULT = "DEFAULT";
      public final static String EMPTY_STRING = "";
      public final static String NOT_YET_IMPLEMENTED = "Not implemented";
      public final static int OUTBOUND = 1;
      public final static int INBOUND = 2;
      
      private final Core core;
/**
 * Insert the method's description here.
 
 */
public AppBase() {
      core = new Core();
      core.err = new ErrHandler(this);
}
/**
 * Insert the method's description here.
 
 * @param b com.midamerican.edi.pgp.BaseEdi
 */
public AppBase(AppBase b) {
      super();
      
      if (b == null) {
            core = new Core();
            core.err = new ErrHandler(this);
            return;
      }
      
      this.core = b.core;
}
/**
 * Insert the method's description here.
 
 */
public TPrintStreamAndLog debugLog() {
      return core.debugLog;
}
/**
 * Insert the method's description here.
 *
 */
public void destroyCore() throws Exception {
      if (core != null) {
            core.destroyCore();
      } else {
            System.out.println("System core not initialized or already destroyed");
      }
}
/**
 * Insert the method's description here.
 *
 */
public ErrHandler errHandler() {
      if (core.err == null)
            printToLog("ErrHandler in AppBase not initialized");
      return core.err;
}
/**
 * Insert the method's description here.
 *
 */
public EventLog eventLog() {
      if (!eventLogInitialized())
            System.out.println("Event Log not initialized");
      return core.eventLog;
}
/**
 * Insert the method's description here.
 *
 */
public boolean eventLogInitialized() {
      return core.eventLog != null;
}
/**
 * Insert the method's description here.
 *
 */
public static String formatDir(String dir) {
      if (dir.endsWith(FS))
            return dir;
      return dir + FS;
}
/**
 * Insert the method's description here.
 *
 */
public com.transport.alarm.AlarmerDaemon getAlarmer() {
      return getSystemServerApp().getAlarmer();
}
/**
 * Insert the method's description here.
 *
 */
public String getBinDir() {
      return getRootDir() + "bin" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public CommServer getCommServer() {
      return core.commServer;
}
/**
 * Insert the method's description here.
 *
 * @return java.lang.String
 */
public java.lang.String getConfigDir() {
      return getRootDir() + "config" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public String getDbDir() {
      return getRootDir() + "db" + FS;
}
/**
 * Insert the method's description here.
 *
 * @return java.lang.String
 */
public java.lang.String getDefaultErrorDir() {
      return getRootParentDir() + "files" + FS + "error" + FS;      
}
/**
 * Insert the method's description here.
 *
 * @return java.lang.String
 */
public java.lang.String getDefaultInboxDir() {
      return getRootParentDir() + "files" + FS + "inbound" + FS + "default_inbox" + FS;      
}
/**
 * Insert the method's description here.
 *
 * @return java.lang.String
 */
public java.lang.String getDefaultOutboxDir() {
      return getRootParentDir() + "files" + FS + "outbound" + FS + "default_outbox" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public String getExternalBinDir() {
      return getExternalDir() + "bin" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public String getExternalClassDir() {
      return getExternalDir() + "classes" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public String getExternalDir() {
      return getRootParentDir() + "external" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public String getExternalDocDir() {
      return getExternalDir() + "doc" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public String getExternalRemoteClassDir() {
      return getExternalDir() + "remote" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public String getFrontEndDir() {
      return getRootDir() + "frontend" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public String getGuiConfigDir() {
      return getFrontEndDir() + "config" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public String getGuiLogsDir() {
      return getFrontEndDir() + "logs" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public String getHelpDir() {
      return getRootParentDir() + "help" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public String getImageDir() {
      return getRootDir() + "image" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public String getLogDir() {
      if (core.logDir != null)
            return core.logDir;
      return getMainLogDir();
}
/**
 * Insert the method's description here.
 *
 */
public String getMainLogDir() {
      return getRootDir() + "logs" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public String getPatternDir() {
      return getRootDir() + "pattern" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public ConfigFile getProgramConfig() throws Exception {
      ConfigFile cf = new ConfigFile(new java.io.File(getConfigDir() + programConfigName));
      cf.setFirstSectionAsCurrent();
      return cf;
}
/**
 * Insert the method's description here.
 *
 */
public String getProjectName() {
      return core.projectName;
}
/**
 * Insert the method's description here.
 *
 */
public java.lang.String getRootDir() {
      if (core.rootDir == null)
            return "Root dir not initialized";
      return core.rootDir;
}
/**
 * Insert the method's description here.
 *
 */
public String getRootParentDir() {
      String r = getRootDir();
      int i = r.lastIndexOf(FS);
      i = r.lastIndexOf(FS, i - 1);
      if (i == -1)
            return("Wrong path in root dir " + r);
      return r.substring(0, i + 1);
}
/**
 * Insert the method's description here.
 *
 */
public Scheduler getScheduler() {
      return core.scheduler;
}
/**
 * Insert the method's description here.
 *
 * @return java.lang.String
 */
public java.lang.String getSecurityDir() {
      return getRootDir() + "security" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public Sequence getSequence() {
      return core.sequence;
}
/**
 * Insert the method's description here.
 *
 */
public int getServerPortFromConfig() throws Exception {
      ConfigFile cf = getProgramConfig();
      return cf.getInt("server_port");
}
/**
 * Insert the method's description here.
 *
 */
public java.util.Date getStartDate() {
      return core.startDate;
}
/**
 * Insert the method's description here.
 *
 */
public SystemServerApp getSystemServerApp() {
      return core.systemServerApp;
}
/**
 * Insert the method's description here.
 *
 * @return java.lang.String
 */
public java.lang.String getTempDir() {
      return getRootDir() + "temp" + FS;
}
/**
 * Insert the method's description here.
 *
 * @return java.lang.String
 */
public java.lang.String getTmpConfigDir() {
      return getRootDir() + "tmp" + FS + "config" + FS;
}
/**
 * Insert the method's description here.
 *
 */
public void initBase() throws Exception {
      if (core.initialized)
            throw new Exception("Core already initialized");

      if (core.rootDir == null)
            initRootDir();

      ConfigFile cf = getProgramConfig();
      core.sequence = new Sequence(this, getRootDir());
      core.debug = new DebugLevel(cf.getString("debug"));
      core.logdebug = new DebugLevel(cf.getString("log_debug"));
      initDebugStreams();
      errHandler().init(getLogDir(), cf);
      setStatusLog(new StatusLog(getLogDir(), getDbDir()));
      setEventLog(new EventLog(getLogDir()));
      core.projectName = cf.getString("project_name");
      core.initialized = true;
}
/**
 * Insert the method's description here.
 *
 */
private void initDebugStreams() throws Exception  {
      if (core.debugLog != null)
            core.debugLog.close();

      Log log = core.logdebug.isTrue() ? new Log(getLogDir(), Debuger.DEBUG_LOG_NAME) : null;
            
      setDebugLog(new TPrintStreamAndLog(
            core.debug.isTrue() ? core.systemOut : null,
            log));      
}
/**
 * Insert the method's description here.
 *
public void initRootDir() {
      if (core.rootDir != null)
            return;
            
      setRootDir(Option.getSystemRootDir());
}
/**
 * Insert the method's description here.
 *
 */
public boolean isDebug() {
      return core.debug.isTrue();
}
/**
 * Insert the method's description here.
 *
 */
public final static boolean isDefault(String str) {
      return str != null && str.equals(DEFAULT);
}
/**
 * Insert the method's description here.
 *
 */
public boolean isEmpty(String value) {
      return value == null || value.trim().length() == 0;
}
/**
 * Insert the method's description here.
 *
 */
public final static boolean isNone(String str) {
      return Tools.isNone(str);
}
/**
 * Insert the method's description here.
 *
 */
public void printlnInfo(String msg) {
      if (core.systemOut != null)
            core.systemOut.println(msg);
}
/**
 * Insert the method's description here.
 *
 */
public void printToLog(long level, String msg) {
      if (core.debug.isSet(level))
            core.systemOut.println(msg);
            
      if (core.logdebug.isSet(level) && core.debugLog.getFileLogger() != null)
            core.debugLog.getFileLogger().println(msg);
}
/**
 * Insert the method's description here.
 *
 */
public void printToLog(String msg) {
      System.out.println(msg);
}
/**
 * Insert the method's description here.
 *
 */
public void setCommServer(CommServer serv) {
      core.commServer = serv;
}
/**
 * Insert the method's description here.
 *
 * @param pr java.io.PrintStream
 */
public void setDebugLog(TPrintStreamAndLog pr) {
      core.debugLog = pr;
      System.setOut(pr);
      System.setErr(pr);
}
/**
 * Insert the method's description here.
 *
 */
public void setErrHandler(ErrHandler eh) {
      core.err = eh;
}
/**
 * Insert the method's description here.
 *
 */
public void setEventLog(EventLog newEventLog) {
      core.eventLog = newEventLog;
}
/**
 * Insert the method's description here.
 *
 */
public void setLogDir(String newLogDir) {
      core.logDir = newLogDir;
}
/**
 * Insert the method's description here.
 *
 */
public void setProjectName(String newName) {
      core.projectName = newName;
}
/**
 * Insert the method's description here.
 *
 */
public void setRootDir(String newRootDir) {
      core.rootDir = formatDir(newRootDir);
}
/**
 * Insert the method's description here.
 *
 */
public void setScheduler(Scheduler sched) {
      core.scheduler = sched;
}
/**
 * Insert the method's description here.
 *
 */
public void setStatusLog(StatusLog newStatusLog) {
      core.statusLog = newStatusLog;
}
/**
 * Insert the method's description here.
 *
 */
public void setSystemServerApp(SystemServerApp app) {
      core.systemServerApp = app;
}
/**
 * Insert the method's description here.
 *
 */
public StatusLog statusLog() {
      if (core.statusLog == null)
            System.out.println("Status Log not initialized");
      return core.statusLog;
}
/**
 * Insert the method's description here.
 *
 */
public synchronized void toExternalLog(String str) throws Exception {
      java.io.FileWriter out = new java.io.FileWriter(getLogDir() + com.transport.external.ExternalProcess.LOG_NAME, true);
      out.write("************************************************" + Log.LINESEP);
      out.write("Result from: " + new java.util.Date() + Log.LINESEP + Log.LINESEP);
      out.write(str);
      out.write(Log.LINESEP + Log.LINESEP);
      out.close();
}

/**
 * Insert the method's description here.
 *
 */
public String getExternalConfigDir() {
      return getExternalDir() + "config" + FS;
}
}

***************************************************************************************
Core class .......................


package com.transport;

import com.transport.log.StatusLog;
import com.transport.log.EventLog;
import com.transport.log.Log;
import com.transport.remote.CommServer;
import com.transport.scheduler.Scheduler;
import com.transport.launch.SystemServerApp;
import com.transport.error.ErrHandler;

/**
 * Insert the type's description here.
 *
 */
public class Core {
      // Keeps original output stream
      public java.io.PrintStream systemOut = System.out;
      
      // Keeps original error stream
      public java.io.PrintStream systemErr = System.err;

      // Store and access status database/log
      public StatusLog statusLog = null;

      // Events
      public EventLog eventLog = null;

      // This is now in place of System.out      
      public TPrintStreamAndLog debugLog = null;

      //// Debug log
      //public Log fileDebugLog = null;

      // Error log
      public ErrHandler err = null;

      // Screen debuging level (what to show on the screen)
      public DebugLevel debug = new DebugLevel();

      // File log debuging level (what to write to log)
      public DebugLevel logdebug = new DebugLevel();

      // Stores absolute root directory (transport/app)
      public String rootDir = null;

      // Sequence
      public Sequence sequence = null;

      // Project name (stored in configuration)
      public String projectName = "Unknown";

      // Scheduler process
      public Scheduler scheduler = null;

      // EDX server
      public CommServer commServer = null;

      // Datetime of system start
      public final java.util.Date startDate = new java.util.Date();

      // Application
      public SystemServerApp systemServerApp;

      // Here are temporary values until GUI is separated
      public String logDir;

      public boolean initialized = false;
/**
 * Core constructor comment.
 */
public Core() {
      super();
}
/**
 * Insert the method's description here.
*/
public void destroyCore() throws Exception {
      if (systemOut != null) {
            System.setOut(systemOut);
            systemOut = null;
      }

      if (systemErr != null) {
            System.setOut(systemErr);
            systemErr = null;
      }
      
      if (sequence != null) {
            sequence.close();
            sequence = null;
      }

      if (err != null) {
            err.destroy();
            err = null;
      }
      if (statusLog != null) {
            statusLog.close();
            statusLog = null;
      }
      if (eventLog != null) {
            eventLog.close();
            eventLog = null;
      }      
      if (debugLog != null) {
            debugLog.close();
            debugLog = null;
      }      
}
/**
 * Code to perform when this object is garbage collected.
 *
 * Any exception thrown by a finalize method causes the finalization to
 * halt. But otherwise, it is ignored.
 */
protected void finalize() throws Throwable {
      destroyCore();
      super.finalize();
}
}


Thanks,

> let me know why would some one need a core class with similar functionality.

The AppBase class provides the functionality by usinmg the core class
ie. without the core class it would be unable to provide that functionality

>> The AppBase class provides the functionality by usinmg the core class

Can you explain this in detail?

Thanks for your help.

:-)