June 2014

You can run application using java by passing command to exec method of java.lang.Runtime object. Here is a sample code for opening calculator in java on Windows or Linux(Ubuntu).

save the below code with name RunApplication.java

package com.trickyjava.general;

public class RunApplication {

 public static void main(String[] args) {
  try {
   String command = getCalculatorCommand();
   if (null == command) {
    throw new Exception("Command Not found");
   }
   System.out.println("Opening Calculator");
   Runtime runTime = Runtime.getRuntime();
   Process process = runTime.exec(command);
   Thread.sleep(5000);
   System.out.println("Closing Calculator");
   process.destroy();
  } catch (Exception e) {
   e.printStackTrace();
  }
 }

 public static String getCalculatorCommand() {
  String OS = System.getProperty("os.name").toLowerCase();
  if (OS.startsWith("windows")) {
   return "calc";
  } else if (OS.startsWith("linux")) {
   return "gcalctool";
  }
  return null;
 }
}

its method getCalculatorCommand() is used to find-out the Operating Specific command. We have made compatible for Windows and Linux.

Output of the following code:

Opening Calculator

Closing Calculator

java.lang.Properties object holds properties information of current runtime environment. Properties class is an implementation of HashTable, it contains information in the form of Key/Value pairs. System class has five methods to play with system properties.

These methods are :

Getter methods
System.getProperties();
System.getProperty(String key);
System.getProperty(String key, String def);

Setter methods

System.setProperties(Properties properties);

System.setProperty(String key,String value);

To list the system properties save the below code with name ListSystemProperties.java

package com.trickyjava.general;

import java.util.Map.Entry;
import java.util.Properties;

public class ListSystemProperties {

 public static void main(String[] args) {
  Properties properties = System.getProperties();
  for (Entry<Object, Object> entry : properties.entrySet()) {
   System.out.println(entry.getKey() + " : " + entry.getValue());
  }
 }
}

And the output of above code will like:

java.runtime.name : OpenJDK Runtime Environment
sun.boot.library.path : /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386
java.vm.version : 24.51-b03
java.vm.vendor : Oracle Corporation
java.vendor.url : http://java.oracle.com/
path.separator : :
java.vm.name : OpenJDK Server VM
file.encoding.pkg : sun.io
user.country : IN
sun.java.launcher : SUN_STANDARD
sun.os.patch.level : unknown
java.vm.specification.name : Java Virtual Machine Specification
user.dir : /home/trickyJavaAdmin/WORK/WORKSPACE/TrickyJavaCode
java.runtime.version : 1.7.0_55-b14
java.awt.graphicsenv : sun.awt.X11GraphicsEnvironment
java.endorsed.dirs : /usr/lib/jvm/java-7-openjdk-i386/jre/lib/endorsed
os.arch : i386
java.io.tmpdir : /tmp
line.separator : 

java.vm.specification.vendor : Oracle Corporation
os.name : Linux
sun.jnu.encoding : UTF-8
java.library.path : /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/server:/usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386:/usr/lib/jvm/java-7-openjdk-i386/jre/../lib/i386:/usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client:/usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386::/usr/java/packages/lib/i386:/usr/lib/i386-linux-gnu/jni:/lib/i386-linux-gnu:/usr/lib/i386-linux-gnu:/usr/lib/jni:/lib:/usr/lib
java.specification.name : Java Platform API Specification
java.class.version : 51.0
sun.management.compiler : HotSpot Tiered Compilers
os.version : 3.8.0-34-generic
user.home : /home/trickyJavaAdmin
user.timezone : 
java.awt.printerjob : sun.print.PSPrinterJob
file.encoding : UTF-8
java.specification.version : 1.7
java.class.path : /home/trickyJavaAdmin/WORK/WORKSPACE/TestJava/bin:/home/trickyJavaAdmin/Downloads/google-api-translate-java-0.97.jar
user.name : trickyJavaAdmin
java.vm.specification.version : 1.7
sun.java.command : com.trickyjava.general.ListSystemProperties
java.home : /usr/lib/jvm/java-7-openjdk-i386/jre
sun.arch.data.model : 32
user.language : en
java.specification.vendor : Oracle Corporation
awt.toolkit : sun.awt.X11.XToolkit
java.vm.info : mixed mode
java.version : 1.7.0_55
java.ext.dirs : /usr/lib/jvm/java-7-openjdk-i386/jre/lib/ext:/usr/java/packages/lib/ext
sun.boot.class.path : /usr/lib/jvm/java-7-openjdk-i386/jre/lib/resources.jar:/usr/lib/jvm/java-7-openjdk-i386/jre/lib/rt.jar:/usr/lib/jvm/java-7-openjdk-i386/jre/lib/sunrsasign.jar:/usr/lib/jvm/java-7-openjdk-i386/jre/lib/jsse.jar:/usr/lib/jvm/java-7-openjdk-i386/jre/lib/jce.jar:/usr/lib/jvm/java-7-openjdk-i386/jre/lib/charsets.jar:/usr/lib/jvm/java-7-openjdk-i386/jre/lib/netx.jar:/usr/lib/jvm/java-7-openjdk-i386/jre/lib/plugin.jar:/usr/lib/jvm/java-7-openjdk-i386/jre/lib/rhino.jar:/usr/lib/jvm/java-7-openjdk-i386/jre/lib/jfr.jar:/usr/lib/jvm/java-7-openjdk-i386/jre/classes
java.vendor : Oracle Corporation
file.separator : /
java.vendor.url.bug : http://bugreport.sun.com/bugreport/
sun.io.unicode.encoding : UnicodeLittle
sun.cpu.endian : little
sun.desktop : gnome
sun.cpu.isalist :

If you want sorted( by property key) list then replace the code main method with the below code

Properties properties = System.getProperties();
Map<Object, Object> propertiesMap = new TreeMap<>(properties);
for (Entry<Object, Object> entry : propertiesMap.entrySet()) {
 System.out.println(entry.getKey() + " : " + entry.getValue());
}

To set the System properties save the below code with name SetSystemProperties.java

package com.trickyjava.general;

public class SetSystemProperties {

 public static void main(String[] args) {
  System.setProperty("movies.home", "/home/trickyJavaAdmin/movies");
  System.setProperty("movies.home.hollywood", "/home/trickyJavaAdmin/movies/hollywoodmovies");
  System.setProperty("movies.home.bollywood", "/home/trickyJavaAdmin/movies/bollywoodmovies");
  
  System.out.println("Movies Directory : "+System.getProperty("movies.home"));
  System.out.println("Hollywood Movies Directory : "+System.getProperty("movies.home.hollywood"));
  System.out.println("Bollywood Movies Directory : "+System.getProperty("movies.home.bollywood"));
 }
}

Output of above code :

Movies Directory : /home/trickyJavaAdmin/movies
Hollywood Movies Directory : /home/trickyJavaAdmin/movies/hollywoodmovies
Bollywood Movies Directory : /home/trickyJavaAdmin/movies/bollywoodmovies

Tricky {Java}

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Tuesday, 24 June 2014

Run application using java

Play with System Properties

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