Technical differences are a consequence of the goal of each one (OpenJDK is meant to be the reference implementation, open to the community, while Oracle is meant to be a commercial one)

They both have &quot;almost&quot; the same code of the classes in the Java API; but the code for the virtual machine itself is actually different, and when it comes to libraries, OpenJDK tends to use open libraries while Oracle tends to use closed ones; for instance,  [the font library](http://technfun.wordpress.com/2013/01/18/last-difference-openjdk-oracle-jdk). 



OpenJDK is a reference model and open source, while Oracle JDK is an implementation of the OpenJDK and is not open source. Oracle JDK is more stable than OpenJDK.

OpenJDK is released under GPL v2 license whereas Oracle JDK is licensed under Oracle Binary Code License Agreement.

OpenJDK and Oracle JDK have almost the same code, but Oracle JDK has more classes and some bugs fixed.

So if you want to develop enterprise/commercial software I would suggest to go for Oracle JDK, as it is thoroughly tested and stable.

I have faced lot of problems with application crashes using OpenJDK, which are fixed just by switching to Oracle JDK


I have two objects of **DateTime**, which need to find the **duration of their difference**, 

I have the following code but not sure how to continue it to get to the expected results as following:

**Example**:

          11/03/14 09:30:58
          11/03/14 09:33:43
          elapsed time is 02 minutes and 45 seconds
          -----------------------------------------------------
          11/03/14 09:30:58 
          11/03/15 09:30:58
          elapsed time is a day
          -----------------------------------------------------
          11/03/14 09:30:58 
          11/03/16 09:30:58
          elapsed time is two days
          -----------------------------------------------------
          11/03/14 09:30:58 
          11/03/16 09:35:58
          elapsed time is two days and 05 minutes
          

**Code**: 

        String dateStart = &quot;11/03/14 09:29:58&quot;;
        String dateStop = &quot;11/03/14 09:33:43&quot;;

        Custom date format
        SimpleDateFormat format = new SimpleDateFormat(&quot;yy/MM/dd HH:mm:ss&quot;);

        Date d1 = null;
        Date d2 = null;
        try {
            d1 = format.parse(dateStart);
            d2 = format.parse(dateStop);
        } catch (ParseException e) {
            e.printStackTrace();
        }

        // Get msec from each, and subtract.
        long diff = d2.getTime() - d1.getTime();
        long diffSeconds = diff / 1000 % 60;
        long diffMinutes = diff / (60 * 1000) % 60;
        long diffHours = diff / (60 * 60 * 1000);
        System.out.println(&quot;Time in seconds: &quot; + diffSeconds + &quot; seconds.&quot;);
        System.out.println(&quot;Time in minutes: &quot; + diffMinutes + &quot; minutes.&quot;);
        System.out.println(&quot;Time in hours: &quot; + diffHours + &quot; hours.&quot;);


How to find the duration of difference between two dates in java?

    class Clstest{
    
    	public static String testStaticMethod(String inFileStr) {
    		
    		// section 0
    		
    		// section 1
    		
    		// do something with inFileStr
    		
    		// section 2
    		
    		// section 3
    		
    		return inFileStr;
    
    	}
    
    }

Let&#39;s assume there are five threads are each executing a call to `Clstest.testStaticMethod(&quot;arg-n&quot;)` at the same time.

Thread 1 calls `Clstest.testStaticMethod(&quot;arg-1&quot;)`.

When thread 1 is in the section 1, thread 2 calls `Clstest.testStaticMethod(&quot;arg-2&quot;)`.

Then what will happen to Thread 1? Will it go to sleep state?

When Thread 1 got the chance will it resume the execution from section 1 where it was paused?

How it happens when there&#39;s one `Clstest.testStaticMethod` and same `Clstest.testStaticMethod` is shared between all five threads?

Is there any possibility to interchange the `inFileStr` sent by multiple threads?

Static method behavior in multi-threaded environment in java

I have been using OpenJDK for ages, initially for small projects where it has no problems. But since I started to play with it for big toys, I started to notice random/unknown fatal error and crashes (with H.264 codecs, etc.), and it was a nightmare till then to get ride of system crash+fatal errors caused by OpenJDK.

After getting completely frustrated and tired with OpenJDK, I finally decided to switch into Oracle JDK 7. Since then my fatal errors/crashes were gone. I am still doing trace to see if it occurs, but I never got those system crashes yet.

Now I am wondering, if OpenJDK is only a license issue, why is stability impossible with it?

Why does OpenJDK keep bugs alive, inside their stable releases, but claiming that its clone of Oracle JDK (which it is not really), then what really technically separates OpenJDK from Oracle JDK? (only quick features availability? Or focused on stability/reliability?)



Technically what is the main difference between Oracle JDK and OpenJDK?

I have been using OpenJDK for ages, initially for small projects where it has no problems. But since I started to play with it for big toys, I started to notice random/unknown fatal error and crashes (with H.264 codecs, etc.), and it was a nightmare till then to get ride of system crash+fatal errors caused by OpenJDK.
After getting completely frustrated and tired with OpenJDK, I finally decided to switch into Oracle JDK 7. Since then my fatal errors/crashes were gone. I am still doing trace to see if it occurs, but I never got those system crashes yet.
Now I am wondering, if OpenJDK is only a license issue, why is stability impossible with it?
Why does OpenJDK keep bugs alive, inside their stable releases, but claiming that its clone of Oracle JDK (which it is not really), then what really technically separates OpenJDK from Oracle JDK? (only quick features availability? Or focused on stability/reliability?)

I&#39;m looking for something to achieve the following:

    String s = &quot;hello {}!&quot;;
    s = generate(s, new Object[]{ &quot;world&quot; });
    assertEquals(s, &quot;hello world!&quot;); // should be true

I could write it myself, but It seems to me that I saw a library once which did this, probably it was the slf4j logger, but i don&#39;t want to write log messages. I just want to generate strings.

Do you know about a library which does this?

Java generating Strings with placeholders

I&#39;m verifying with mockito that a method has been called. The method:

    public void createButtons(final List&lt;Button&gt; buttonsConfiguration) {...}

Since It doesn&#39;t matter which list is passed I verify that the method is called as follows:

    verify(mock).createButtons(Matchers.anyListOf(Button.class));

But, the size of the `List` is important. So, it doesn&#39;t matter which `List` but the list has to have X elements.

Is that possible at all?

mockito anyList of a given size

There are similar questions out there, but they seem to avoid answering this specific question.  How can I get the memory that **my Java program** uses via Java&#39;s Runtime api?

**The answer [here][1] indicates that I can do something like this:**

    System.out.println(&quot;KB: &quot; + (double) (Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory()) / 1024);

But this always returns the same number, no matter which program I run.  For example, below I have a program where no matter how many numbers I put in the map, the memory usage stays the same.

    package memoryTest;
    
    import java.util.HashMap;
    import java.util.Map;
    
    public class MemoryTest {
    
        static Map&lt;Integer, NewObject&gt; map = new HashMap&lt;Integer, NewObject&gt;();
    
        public static void main(String[] args){
    
            System.out.println(&quot;KB: &quot; + (double) (Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory()) / 1024);
            fillMemory(25);
    
            System.out.println(&quot;KB: &quot; + (double) (Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory()) / 1024);
        }
    
        static int j=0;
        public static void fillMemory(int i){
    
            for(int k=0; k&lt; 2000; k++)
                map.put(j++, new NewObject());
    
        }
        
    
        public static class NewObject{
            long i = 0L;
            long j = 0L;
            long k = 0L;
        }
        
    }

via cambecc&#39;s main method, output is:

# 3085, Total: 128516096, Free: 127173744, Diff: 671120
# 173579, Total: 128516096, Free: 110033976, Diff: 671128
# 335207, Total: 128516096, Free: 92417792, Diff: 637544
# 672788, Total: 224198656, Free: 159302960, Diff: 1221520
# 1171480, Total: 224198656, Free: 106939136, Diff: 1221544
# 1489771, Total: 368377856, Free: 227374816, Diff: 1212984
# 1998743, Total: 368377856, Free: 182494408, Diff: 1212984


  [1]: https://stackoverflow.com/questions/3571203/what-is-the-exact-meaning-of-runtime-getruntime-totalmemory-and-freememory

How can I get the memory that my Java program uses via Java&#39;s Runtime api?

There are two types of iterators in Java: fail-safe and fail-fast.

What does this mean, and is the difference between them?

What are fail-safe &amp; fail-fast Iterators in Java

    import java.awt.List;
    import java.awt.image.BufferedImage;
    import java.io.BufferedReader;
    import java.io.ByteArrayOutputStream;
    import java.io.File;
    import java.io.InputStreamReader;
    import java.util.ArrayList;

    import javax.imageio.ImageIO;

    import org.apache.commons.codec.binary.Base64;
    import org.apache.http.HttpResponse;
    import org.apache.http.client.HttpClient;
    import org.apache.http.client.entity.UrlEncodedFormEntity;
    import org.apache.http.client.methods.HttpPost;
    import org.apache.http.impl.client.DefaultHttpClient;
    import org.apache.http.message.BasicNameValuePair;
    import org.omg.DynamicAny.NameValuePair;
    
    public class Upload {
    	
    	public static void main (String[] args) {
    		
    		System.out.println(Imgur(&quot;C:\\Users\\username\\Desktop\\image.jpg&quot;,     &quot;clientID&quot;));
    	}
    
    public static String Imgur (String imageDir, String clientID) {
        //create needed strings
        String address = &quot;https://api.imgur.com/3/image&quot;;
    
        //Create HTTPClient and post
        HttpClient client = new DefaultHttpClient();
        HttpPost post = new HttpPost(address);
    
        //create base64 image
        BufferedImage image = null;
        File file = new File(imageDir);
    
        try {
            //read image
            image = ImageIO.read(file);
            ByteArrayOutputStream byteArray = new ByteArrayOutputStream();
            ImageIO.write(image, &quot;png&quot;, byteArray);
            byte[] byteImage = byteArray.toByteArray();
            String dataImage = new Base64().encodeAsString(byteImage);
    
            //add header
            post.addHeader(&quot;Authorization&quot;, &quot;Client-ID&quot; + clientID);
            //add image
            List&lt;NameValuePair&gt; nameValuePairs = new ArrayList&lt;NameValuePair&gt;(1);
            nameValuePairs.add(new BasicNameValuePair(&quot;image&quot;, dataImage));
            post.setEntity(new UrlEncodedFormEntity(nameValuePairs));
    
            //execute
            HttpResponse response = client.execute(post);
    
            //read response
            BufferedReader rd = new BufferedReader(new         InputStreamReader(response.getEntity().getContent()));
            String all = null;
    
            //loop through response
            while (rd.readLine() != null) {
                all = all + &quot; : &quot; + rd.readLine(); 
            }
    
            return all;
    
        }
        catch (Exception e){
            return &quot;error: &quot; + e.toString();
        }
    }
    }

So I have that code and I got it from https://stackoverflow.com/questions/14710247/uploading-to-imgur-v3-using-java-https-errors and I get an error on line 50 for &quot;List&quot; telling me

&gt; The type List is not generic; it cannot be parameterized with arguments &lt;NameValuePair&gt;

What can I do to solve this?

I&#39;m using http://hc.apache.org/httpclient-3.x/ and want to upload an image to imgur using their v3 API.

EDIT: After changing the import I now get these errors.

That solves that but give me two more errors. 

    nameValuePairs.add(new BasicNameValuePair(&quot;image&quot;, dataImage));

&gt; The method add(NameValuePair) in the type List&lt;NameValuePair&gt; is not applicable for the arguments (BasicNameValuePair)

And

`post.setEntity(new UrlEncodedFormEntity(nameValuePairs)); ` 

&gt; The constructor UrlEncodedFormEntity(List&lt;NameValuePair&gt;) is undefined 


The type List is not generic; it cannot be parameterized with arguments [HTTPClient]

I&#39;m running a nohup process on the server. When I try to kill it my putty console closes instead.

this is how I try to find the process ID:

    ps -ef |grep nohup 

this is the command to kill
    
     kill -9 1787 787

How to get the process ID to kill a nohup process?

We have multiple servers in our lab and I tried to determine which one has more resources currently available. I tried to interpret the information htop displays but I&#39;m not 100% understanding all those numbers. 

I have taken a screen shot for each server after issuing htop:


Server #1:

![][1]

Server #2: 

![][2] 

Does server #1 have more memory available than server #2? Should I look at Avg or Mem? Or what other parameter should I look at?

Thanks!


 [1]:http://i.imgur.com/zIEqjOj.jpg
 [2]:http://i.imgur.com/vjEcyzA.jpg

How do I interpret the memory usage information from htop

I was using ubuntu 12.04 ,on which I run ulimit -n ,it is showing 1024,
I want to increase my open file limit from 1024 to 65535,so I tried the following command:
    
    sudo ulimit -n 65535

but i get the following error:

    sudo: ulimit: command not found


How to increase the file limit from 1024 to 65535? Any help will be appreciated.

 

command not found when using sudo ulimit

I&#39;m trying to change the message of the day (MOTD) on my Ubuntu Amazon EC2 box so that it will display the git status of one of my directories when I SSH in.

The output from all of the default MOTD files have two spaces at the start of each line so it looks nicely indented, but because my `git status` output spans several lines, if I do `echo -n &quot;  &quot;` before it only indents the first line.

Any idea how I can get it to indent every line?

Indenting multi-line output in a shell script

Time and time again, I see Bash answers on Stack Overflow using `eval` and the answers get bashed, pun intended, for the use of such an &quot;evil&quot; construct. Why is `eval` so evil?

If `eval` can&#39;t be used safely, what should I use instead?

Why should eval be avoided in Bash, and what should I use instead?

I know that a method cannot be larger than 64&amp;nbsp;KB with Java. The limitation causes us problems with generated code from a [JavaCC][1] grammar. We had problems with Java 6 and were able to fix this by changing the grammar. Has the limit been changed for Java 7 or is it planned for Java 8?

Just to make it clear. I don&#39;t need a method larger than 64&amp;nbsp;KB by myself. But I wrote a grammar which compiles to a very large method.

  [1]: http://en.wikipedia.org/wiki/JavaCC


Maximum size of a method in Java 7 and 8

I&#39;m getting following error when trying to compile my project in Android Studio:

    Gradle: error: diamond operator is not supported in -source 1.6

I have 1.7 set as target in all project preferences I&#39;ve found. Also the path displayed in project SDK&#39;s under 1.7 SDK is correct path to java 1.7 installation.

Even when I run java -version in terminal, it tells me I&#39;m running on java 1.7.

I have tried to set JAVA_HOME env variable to this:

    /Library/Java/JavaVirtualMachines/jdk1.7.0_25.jdk/Contents/Home

The error does not go away.  How do I eliminate the error?


How to set -source 1.7 in Android Studio and Gradle

I am expecting the buffered reader and file reader to close and the resources released if the exception is throw.

	public static Object[] fromFile(String filePath) throws FileNotFoundException, IOException
	{
		try (BufferedReader br = new BufferedReader(new FileReader(filePath)))
		{
			return read(br);
		} 
	}

However, is there a requirement to have a `catch` clause for successful closure?

**EDIT:**

Essentially, is the above code in Java 7 equivalent to the below for Java 6:

    public static Object[] fromFile(String filePath) throws FileNotFoundException, IOException
    {

	    BufferedReader br = null;
	
	    try
        {
	    	br = new BufferedReader(new FileReader(filePath));
		
            return read(br);
        }
    	catch (Exception ex)
    	{
    		throw ex;
    	}
    	finally
    	{
    		try
    		{
    			if (br != null) br.close();
    		}
    		catch(Exception ex)
    		{
    		}
    	}
    	
    	return null;
    }


Am I using the Java 7 try-with-resources correctly

Java 7 has a new feature called [try-with-resources][1]. What is it? Why and where we should use it and where we can take advantage of this feature?

The `try` statement has no `catch` block which confuses me.


  [1]: http://docs.oracle.com/javase/7/docs/technotes/guides/language/try-with-resources.html

What&#39;s the purpose of try-with-resources statements?

I am a new comer to the android world and with a .NET background. I am trying to install the Android Studio but I am having a mismatch on Android.com about the JDK version required for developing Android applications.

From the [SDK web page][1] it states that **JDK 6** is required (under system requirements section). [Jim Wilson][2] also insist in [his course on Pluralsight][3] (which is quite new, from last May) that using version 7 with the Android SDK will create a lot of headache and makes it clear to only use JDK 6. 

Although in the [Android studio page][4] (Under installing step 2) they explain how to set an environment variable indicating the correct JDK location. In here they use a path of **JDK 7**

&gt; Select `Start menu &gt; Computer &gt; System Properties &gt; Advanced System Properties`. Then open `Advanced tab &gt; Environment Variables` and add a new system variable `JAVA_HOME` that points to your JDK folder, for example `C:\Program Files\Java\jdk1.7.0_21`.

I am pretty sure both the ADT &amp; Eclipse bundle and the Android Studio bundle are using the same SDK but now I am confused about which JDK version I need to install. My sole purpose is to avoid problems as much as possible while getting my first steps into the Android development.

Disclaimer: I am not related by any mean to Pluralsight. I am just a normal user following the courses.

  [1]: http://developer.android.com/sdk/index.html
  [2]: http://pluralsight.com/training/Authors/Details/jim-wilson
  [3]: http://www.pluralsight.com/training/Courses/TableOfContents/android-dotnet-developers-getting-started
  [4]: http://developer.android.com/sdk/installing/studio.html#Installing

Content Type	Original Author	Original Content on Stackoverflow
Question	user285594	View Question on Stackoverflow
Solution 1 - Java	morgano	View Answer on Stackoverflow
Solution 2 - Java	User007	View Answer on Stackoverflow

Technically what is the main difference between Oracle JDK and OpenJDK?

Java Problem Overview

Java Solutions

Solution 1 - Java

Solution 2 - Java

Static method behavior in multi-threaded environment in java

How to find the duration of difference between two dates in java?

Attributions