Java/Development Class/System Properties

Check Version

 
//: com:bruceeckel:tools:CheckVersion.java
// {RunByHand}
// From "Thinking in Java, 3rd ed." (c) Bruce Eckel 2002
// www.BruceEckel.ru. See copyright notice in CopyRight.txt.
public class CheckVersion {
  public static void main(String[] args) {
    String version = System.getProperty("java.version");
    char minor = version.charAt(2);
    char point = version.charAt(4);
    if(minor < "4" || point < "1")
      throw new RuntimeException("JDK 1.4.1 or higher " +
        "is required to run the examples in this book.");
    System.out.println("JDK version "+ version + " found");
  }
} ///:~

Clear system property: The System.clearProperty() method available in Java 1.5

 
 
public class Main {
    public static void main(String[] args) {
        String key = "user.dir";
        System.clearProperty(key);
    }
}

Dealing with the Java environment

 
public class GetVersion {
  public static void main(String[] args) {
    System.out.println(System.getProperty("java.specification.version"));
    System.out.println("System.getenv(\"PATH\") = " + System.getenv("PATH"));    
  }
}

Determine operating system using System class

 
public class Main {
  public static void main(String[] args) {
    System.out.println(System.getProperty("os.name"));
  }
}

Display System Properties

 
/* From http://java.sun.ru/docs/books/tutorial/index.html */
/*
 * Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * -Redistribution of source code must retain the above copyright notice, this
 *  list of conditions and the following disclaimer.
 *
 * -Redistribution in binary form must reproduce the above copyright notice,
 *  this list of conditions and the following disclaimer in the documentation
 *  and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 *
 * You acknowledge that this software is not designed, licensed or intended
 * for use in the design, construction, operation or maintenance of any
 * nuclear facility.
 */
public class DisplaySystemProps {
    public static void main(String[] args) {
         System.getProperties().list(System.out);
    }
}

Dump Props

 
import java.util.Enumeration;
import java.util.Iterator;
import java.util.Map;
import java.util.Properties;
public class DumpProps {
  public static void main(String args[]) {
    Properties props = System.getProperties();
    Iterator iter = props.entrySet().iterator();
    while (iter.hasNext()) {
      Map.Entry entry = (Map.Entry) iter.next();
      System.out.println(entry.getKey() + " --- " + entry.getValue());
    }
    System.out.println("-------");
    Enumeration e = props.propertyNames();
    while (e.hasMoreElements()) {
      String key = (String) e.nextElement();
      System.out.println(key + " --- " + props.getProperty(key));
    }
  }
}

Get Environment Variables

 
 
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
public class Main {
  public static void main(String[] args) {
    Map map = System.getenv();
    Set keys = map.keySet();
    Iterator iterator = keys.iterator();
    while (iterator.hasNext()) {
      String key = (String) iterator.next();
      String value = (String) map.get(key);
      System.out.println(key + " = " + value);
    }
  }
}

Get file separator symbol

 
public class Main {
  public static void main(String[] args) {
    String dataFolder = System.getProperty("user.dir") + System.getProperty("file.separator")
        + "data";
    System.out.println("Data Folder = " + dataFolder);
  }
}

Get Java Home directory

 
 
public class Main {
  public static void main(String[] args) {
    String javaHome = System.getProperty("java.home");
    System.out.println("javaHome = " + javaHome);
  }
}

Get Java Runtime Environment (JRE) version?

 
 
public class Main {
  public static void main(String[] args) {
    String version = System.getProperty("java.version");
    System.out.println("JRE Version = " + version);
  }
}

Get Java specification version using System class

 
public class Main {
  public static void main(String[] args) {
    System.out.println(System.getProperty("java.specification.version"));
  }
}

Get operating system name and version

 
public class Main {
  public static void main(String[] args) {
    String name = "os.name";
    String version = "os.version";
    String architecture = "os.arch";
    System.out.println("Name: " + System.getProperty(name));
    System.out.println("Version: " + System.getProperty(version));
    System.out.println("Architecture: " + System.getProperty(architecture));
  }
}

Get operating system temporary directory / folder

 
public class Main {
  public static void main(String[] args) {
    String property = "java.io.tmpdir";
    String tempDir = System.getProperty(property);
    System.out.println("OS current temporary directory is " + tempDir);
  }
}

Get path / classpath separator

 
import java.util.Properties;
public class Main {
  public static void main(String[] args) {
    Properties properties = System.getProperties();
    String pathSeparator = properties.getProperty("path.separator");
    System.out.println("pathSeparator = " + pathSeparator);
  }
}

Get system properties using System class

 
import java.util.Properties;
public class Main {
  public static void main(String[] args) {
    Properties prop = System.getProperties();
    System.out.println("Printing all System properties");
    prop.list(System.out);
  }
}

Get user home directory name

 
public class Main {
  public static void main(String[] args) {
    String userHome = "user.home";
    String path = System.getProperty(userHome);
    System.out.println("Your Home Path: " + path);
  }
}

Get username of system current user

 
 
public class Main {
  public static void main(String[] args) {
    String username = System.getProperty("user.name");
    System.out.println("username = " + username);
  }
}

List one or more item(s) from System Properties

 
/*
 * Copyright (c) Ian F. Darwin, http://www.darwinsys.ru/, 1996-2002.
 * All rights reserved. Software written by Ian F. Darwin and others.
 * $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS""
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 * 
 * Java, the Duke mascot, and all variants of Sun"s Java "steaming coffee
 * cup" logo are trademarks of Sun Microsystems. Sun"s, and James Gosling"s,
 * pioneering role in inventing and promulgating (and standardizing) the Java 
 * language and environment is gratefully acknowledged.
 * 
 * The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
 * inventing predecessor languages C and C++ is also gratefully acknowledged.
 */
import java.io.IOException;
/**
 * List one or more item(s) from System Properties
 */
public class SysPropDemo {
  public static void main(String[] argv) throws IOException {
    if (argv.length == 0)
      System.getProperties().store(System.out, "System Properties:");
    else
      for (int i = 0; i < argv.length; i++) {
        String s = argv[i];
        System.out.println(s + " = "
            + System.getProperties().getProperty(s));
      }
  }
}

Machine User Name

 
/* From http://java.sun.ru/docs/books/tutorial/index.html */
/*
 * Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * -Redistribution of source code must retain the above copyright notice, this
 *  list of conditions and the following disclaimer.
 *
 * -Redistribution in binary form must reproduce the above copyright notice,
 *  this list of conditions and the following disclaimer in the documentation
 *  and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 *
 * You acknowledge that this software is not designed, licensed or intended
 * for use in the design, construction, operation or maintenance of any
 * nuclear facility.
 */
public class UserNameTest {
    public static void main(String[] args) {
        String name = System.getProperty("user.name");
        System.out.println(name);
    }
}

Set a system property

 
public class Main {
  public static void main(String[] argv) throws Exception {
    String previousValue = System.setProperty("application.property", "newValue");
  }
}

Setting the Value of a System Property from the Command Line: add -D option to the java command when running your program.

 

java -Dmy.prop="my value" MyApp

public class Main {
  public static void main(String[] argv) throws Exception {
  
    String prop = System.getProperty("my.prop");
  
  }
}

System.setProperty("apple.laf.useScreenMenuBar", "true")

 
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
public class Main {
  static {
    System.setProperty("apple.laf.useScreenMenuBar", "true");
  }
  public static void main(String[] args) {
    JFrame frame = new JFrame("Menu Bar Demo");
    JMenuBar bar = new JMenuBar();
    JMenu fileMenu = new JMenu("File");
    JMenu editMenu = new JMenu("Edit");
    JMenu helpMenu = new JMenu("Help");
    bar.add(fileMenu);
    bar.add(editMenu);
    bar.add(helpMenu);
    frame.setSize(300, 150);
    frame.setJMenuBar(bar);
    frame.setVisible(true);
  }
}

Use System.getenv to get environment variables

 
/*
 * Copyright (c) 1995 - 2008 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Sun Microsystems nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */ 
public class Env {
    public static void main (String[] args) {
        for (String env: args) {
            String value = System.getenv(env);
            if (value != null) {
                System.out.format("%s=%s%n", env, value);
            } else {
                System.out.format("%s is not assigned.%n", env);
            }
        }
    }
}