Cannot compile Java application

Mon, 01 Nov 2010 04:29:21 -0700

Hello, I am new to Java and programming in general. I have a source of an application written in Java that I want to change a part of and compile it. Here is the file I am working on:

package sarf.ui;

import java.awt.Toolkit;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import java.awt.Dimension;
import javax.swing.plaf.metal.MetalLookAndFeel;
import javax.swing.JOptionPane;

/**
 *

Title:

 *
 *

Description:

 *
 *

Copyright: Copyright (c) 2006

 *
 *

Company:

 *
 * @author not attributable
 * @version 1.0
 */
public class MainApp {
    boolean packFrame = false;

    /**
     * Construct and show the application.
     */
    public MainApp() {
       
        // Center the window

        Dimension frameSize = frame.getSize();
        if (frameSize.height > screenSize.height) {
            frameSize.height = screenSize.height;
        }
        if (frameSize.width > screenSize.width) {
            frameSize.width = screenSize.width;
        }
        frame.setLocation((screenSize.width - frameSize.width) / 2, (screenSize.height - frameSize.height) / 2);
        frame.setVisible(true);
    }

    /**
     * Application entry point.
     *
     * @param args String[]
     */
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                try {
                    //MetalLookAndFeel.setCurrentTheme(new javax.swing.plaf.metal.OceanTheme());
                    UIManager.setLookAndFeel(MetalLookAndFeel.class.ge
tName());
                }
                catch (Exception exception) {
                    exception.printStackTrace();
                }

                new MainApp();
            }
        });
    }
}

When I try to compile it, I get the following error:

[zand@zand ui]$ /opt/java/bin/javac -verbose MainApp.java
[parsing started MainApp.java]
[parsing completed 39ms]
[search path for source files: .]
[search path for class files: /opt/java/jre/lib/resources.jar,/opt/java/jre/lib/
rt.jar,/opt/java/jre/lib/sunrsasign.jar,/opt/java/
jre/lib/jsse.jar,/opt/java/jre/lib/jce.jar,/opt/ja
va/jre/lib/charsets.jar,/opt/java/jre/classes,/opt
/java/jre/lib/ext/dnsns.jar,/opt/java/jre/lib/ext/
localedata.jar,/opt/java/jre/lib/ext/sunjce_provid
er.jar,/opt/java/jre/lib/ext/sunpkcs11.jar,.]
[loading java/awt/Toolkit.class(java/awt:Toolkit.class)]
[loading javax/swing/SwingUtilities.class(javax/swing:Swing
Utilities.class)]
[loading javax/swing/UIManager.class(javax/swing:UIManager.
class)]
[loading java/awt/Dimension.class(java/awt:Dimension.class)
]
[loading javax/swing/plaf/metal/MetalLookAndFeel.class(java
x/swing/plaf/metal:MetalLookAndFeel.class)]
[loading javax/swing/JOptionPane.class(javax/swing:JOptionP
ane.class)]
[loading java/lang/Object.class(java/lang:Object.class)]
[loading java/lang/String.class(java/lang:String.class)]
[checking sarf.ui.MainApp]
MainApp.java:32: cannot find symbol
symbol  : variable frame
location: class sarf.ui.MainApp
        Dimension frameSize = frame.getSize();
                              ^
MainApp.java:33: cannot find symbol
symbol  : variable screenSize
location: class sarf.ui.MainApp
        if (frameSize.height > screenSize.height) {
                               ^
MainApp.java:34: cannot find symbol
symbol  : variable screenSize
location: class sarf.ui.MainApp
            frameSize.height = screenSize.height;
                               ^
MainApp.java:36: cannot find symbol
symbol  : variable screenSize
location: class sarf.ui.MainApp
        if (frameSize.width > screenSize.width) {
                              ^
MainApp.java:37: cannot find symbol
symbol  : variable screenSize
location: class sarf.ui.MainApp
            frameSize.width = screenSize.width;
                              ^
MainApp.java:39: cannot find symbol
symbol  : variable screenSize
location: class sarf.ui.MainApp
        frame.setLocation((screenSize.width - frameSize.width) / 2, (screenSize.height - frameSize.height) / 2);
                           ^
MainApp.java:39: cannot find symbol
symbol  : variable screenSize
location: class sarf.ui.MainApp
        frame.setLocation((screenSize.width - frameSize.width) / 2, (screenSize.height - frameSize.height) / 2);
                                                                     ^
MainApp.java:39: cannot find symbol
symbol  : variable frame
location: class sarf.ui.MainApp
        frame.setLocation((screenSize.width - frameSize.width) / 2, (screenSize.height - frameSize.height) / 2);
        ^
MainApp.java:40: cannot find symbol
symbol  : variable frame
location: class sarf.ui.MainApp
        frame.setVisible(true);
        ^
[loading java/lang/Runnable.class(java/lang:Runnable.class)
]
[loading java/lang/Class.class(java/lang:Class.class)]
[loading javax/swing/LookAndFeel.class(javax/swing:LookAndF
eel.class)]
[loading java/lang/Exception.class(java/lang:Exception.clas
s)]
[loading java/lang/Throwable.class(java/lang:Throwable.clas
s)]
[total 349ms]
9 errors

As far as I understand I am missing some standard class library to work .getSize though it seems to load some classes from /opt/java/jre/lib/.

Re: Cannot compile Java application

Wed, 03 Nov 2010 13:33:13 -0700

Your file is in a package named sarf.ui and this will affect the kind of compiling command you have to use and where to store your file.

Make a file directory structure like this for your code:
sarf
- ui
- - MainApp.java

In other words, make directory sarf. make a directory ui to go within sarf. make file MainApp.java to go within ui.

Your MainApp.java had some undeclared variables like frame and screensize so it was updated to work. Here is the contents of MainApp.java:

package sarf.ui;

import java.awt.Toolkit;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import java.awt.Dimension;
import javax.swing.plaf.metal.MetalLookAndFeel;
import javax.swing.JOptionPane;
import javax.swing.JFrame;

/**
 *

Title:

 *
 *

Description:

 *
 *

Copyright: Copyright (c) 2006

 *
 *

Company:

 *
 * @author not attributable
 * @version 1.0
 */
public class MainApp {
    boolean packFrame = false;
  JFrame frame;

    /**
     * Construct and show the application.
     */
    public MainApp() {
        // create the frame.
        frame = new JFrame("The Window");
        frame.setSize(400,400);
        Toolkit toolkit = Toolkit.getDefaultToolkit();
        Dimension screenSize = toolkit.getScreenSize(); 
       
        // Center the window


        Dimension frameSize = frame.getSize();
        if (frameSize.height > screenSize.height) {
            frameSize.height = screenSize.height;
        }
        if (frameSize.width > screenSize.width) {
            frameSize.width = screenSize.width;
        }
        frame.setLocation((screenSize.width - frameSize.width) / 2, (screenSize.height - frameSize.height) / 2);
        frame.setVisible(true);
    }

    /**
     * Application entry point.
     *
     * @param args String[]
     */
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                try {
                    //MetalLookAndFeel.setCurrentTheme(new javax.swing.plaf.metal.OceanTheme());
                    UIManager.setLookAndFeel(MetalLookAndFeel.class.ge
tName());
                }
                catch (Exception exception) {
                    exception.printStackTrace();
                }

                new MainApp();
            }
        });
    }
}

To compile that from command line, go to the directory above sarf, the root directory of your code. From there, use this command:

javac sarf/ui/*.java

To run the resulting .class file, execute from the same directory as compilation, the following command:

java sarf.ui.MainApp

Without the line "package sarf.ui;" in your code, there would be no need to worry about the directory structure.

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