All standard implementations of `java.util.List` already implement `java.io.Serializable`.

So even though `java.util.List` itself is not a subtype of `java.io.Serializable`, it should be safe to cast the list to `Serializable`, as long as you know it&#39;s one of the standard implementations like `ArrayList` or `LinkedList`.

If you&#39;re not sure, then copy the list first (using something like `new ArrayList(myList)`), then you know it&#39;s serializable.

As pointed out already, most standard implementations of `List` are serializable. However you have to ensure that the objects referenced/contained within the list are *also* serializable.

*List* is just an interface. The question is: is your actual *List* implementation serializable? Speaking about the standard *List* implementations (*ArrayList*, *LinkedList*) from the Java run-time, most of them actually are already.

A common scenario when I develop is that the codebase will have several config files which require machine specific settings. These files will be checked into Git and other developers will always accidentally check them back in and break someone else&#39;s configuration.

A simple solution to this would be to just not check them in to Git, or even to additionally add a .gitignore entry for them. However, I find that it is much more elegant to have some sensible defaults in the file which the developer can modify to suit his needs.

Is there an elegant way to make Git play nicely with such files? I would like to be able to modify a machine-specific configuration file and then be able to run &quot;git commit -a&quot; without checking that file in.

Committing Machine Specific Configuration Files

Why is only XOR used in cryptographic algorithms, and other logic gates like OR, AND, and NOR are not used?

Why is XOR used in cryptography?

I would like to deep clone a List. for that we are having a method

    // apache commons method. This object should be serializable
    SerializationUtils.clone ( object ) 

so now to clone my List i should convert that to serializable first. Is it possible to convert a List into Serializable list?


How to Serialize a list in java?

I would like to deep clone a List. for that we are having a method
<pre><code class="hljs language-php">// apache commons method. This object should be serializable
SerializationUtils.clone ( object ) 
</code></pre>
so now to clone my List i should convert that to serializable first. Is it possible to convert a List into Serializable list?

I&#39;m reading a local file using a BufferedReader wrapped around a FileReader:

    BufferedReader reader = new BufferedReader(new FileReader(fileName));
    // read the file
    // (error handling snipped)
    reader.close();

Do I need to `close()` the `FileReader` as well, or will the wrapper handle that?
I&#39;ve seen code where people do something like this:

    FileReader fReader = new FileReader(fileName);
    BufferedReader bReader = new BufferedReader(fReader);
    // read the file
    // (error handling snipped)
    bReader.close();
    fReader.close();

This method is called from a servlet, and I&#39;d like to make sure I don&#39;t leave any handles open.

Do I need to close() both FileReader and BufferedReader?

We have a simple performance test flow in an application.
 
 1. We login
 2. Search based on some criteria
 3. repeat searches for different parameters. 

We are using Jmeter to do a performance testing. We need to have multiple threads running to test this in a scalable manner.

The way we currently have this arranged is:

    -Test Plan
      - Thread Group
          - Cookie Manager
          - Login To application
          - Search on param 1
          - Search on param 2
      - results summary table
      - Summary report

So basically we have summary return table and report present on plan level while cookie manager is present on thread group level. 

When I run for one thread it runs fine and completes well. When I scale it to multiple threads, as soon as the next thread kicks off, the session for the last thread is invalidated. This causes failures for all the already running threads due to newly spawned thread.

I reached this result with observation:
&lt;br&gt;1. If I run multiple threads, only last thread has got valid responses in result summary tree
&lt;br&gt;2. If I run with 2 threads with ramp up period as 10 seconds, which means each thread gets time to finish itself, then both of them run successfully. 

As per my understanding each thread login&#39;s into application and since cookie manager is at thread level, the values will be maintained for session id for each thread respectively? But what is causing the override of the session id value between threads?

Any help will be much appreciated. 




Session/cookie management in Apache JMeter

I&#39;m looking for the best way to create a unique ID as a String in Java.

Any guidance appreciated, thanks.

I should mention I&#39;m using Java 5.


How do I create a unique ID in Java?

I need to write a custom batch File renamer. I&#39;ve got the bulk of it done except I can&#39;t figure out how to check if a file is already open. I&#39;m just using the `java.io.File` package and there is a `canWrite()` method but that doesn&#39;t seem to test if the file is in use by another program. Any ideas on how I can make this work?

Check if file is already open

I need a data structure that is a LinkedHashMap and is thread safe.

How can I do that ?

Does java have a &quot;LinkedConcurrentHashMap&quot; data structure?

Is there a way in Java/J2ME to convert a string, such as:

    {name:&quot;MyNode&quot;, width:200, height:100}

to an internal Object representation of the same, in one line of code? 

Because the current method is too tedious:

    Object n = create(&quot;new&quot;);
    setString(p, &quot;name&quot;, &quot;MyNode&quot;);
    setInteger(p, &quot;width&quot;, 200);
    setInteger(p, &quot;height&quot;, 100);

Maybe a JSON library?

Convert a JSON string to object in Java ME?

I have a POCO class that is being sent to the browser as a JSON string in .NET 3.5 sp1.  I am just using the default JSON serialization and I have some fields that I want to ignore.  I want to put an attribute similar to [System.Xml.Serialization.XmlIgnore] on them so that they are not serialized.

Ignoring a field during .NET JSON serialization; similar to [XmlIgnore]?

I am using .NET 3.5SP1 and `DataContractSerializer` to serialize a class.  In SP1, they changed the behavior so that you don&#39;t have to include `DataContract`/`DataMember` attributes on the class and it will just serialize the entire thing.  This is the behavior I am using, but now I need to ignore one property from the serializer.  I know that one way to do this is to add the `DataContract` attribute to the class, and just put the `DataMember` attribute on all of the members that I want to include.  I have reasons, though, that this will not work for me.  

So my question is, is there an attribute or something I can use to make the `DataContractSerializer` ignore a property?

How can I ignore a property when serializing using the DataContractSerializer?

Using `$(&#39;#form&#39;).serialize()`, I was able to send this over to a PHP page. Now how do I unserialize it in PHP? It was serialized in jQuery.

How do I PHP-unserialize a jQuery-serialized form?

I would like to get the same effect as `jQuery.serialize()` but I would like to return only the child elments of a given `div`.

**Sample result :**

    single=Single2&amp;multiple=Multiple&amp;radio=radio1

jQuery to serialize only elements within a div

What is the easiest way to convert a `List` to a `Set` in Java?

Easiest way to convert a List to a Set in Java

I was looking for a [bidirectional map](http://en.wikipedia.org/wiki/Bidirectional_map) implementation in Java, and stumbled upon these two libraries:

* [Google Guava](https://github.com/google/guava) (formerly &quot;Google Collections&quot;)
* [Apache Commons Collections](http://commons.apache.org/collections/)

Both are free, have the bidirectional map implementation that I was looking for (BidiMap in Apache, BiMap in Google), are amazingly nearly the same size (Apache 493 kB, Google 499 kB) [ed.: no longer true!] and seem in all ways pretty similar to me.

Which one should I choose, and why? Are there some other equivalent alternatives (must be free and have at least the bidirectional map)? I&#39;m working with the latest Java SE, so no need to artificially limit to Java 5 or anything like that.

Google Guava vs. Apache Commons

A coworker asked me today how to add a range to a collection. He has a class that inherits from `Collection&lt;T&gt;`. There&#39;s a get-only property of that type that already contains some items. He wants to add the items in another collection to the property collection. How can he do so in a C#3-friendly fashion? *(Note the constraint about the get-only property, which prevents solutions like doing Union and reassigning.)*

Sure, a foreach with Property. Add will work. But a `List&lt;T&gt;`-style AddRange would be far more elegant.

It&#39;s easy enough to write an extension method:

    public static class CollectionHelpers
    {
        public static void AddRange&lt;T&gt;(this ICollection&lt;T&gt; destination,
                                       IEnumerable&lt;T&gt; source)
        {
            foreach (T item in source)
            {
                destination.Add(item);
            }
        }
    }

But I have the feeling I&#39;m reinventing the wheel. I didn&#39;t find anything similar in `System.Linq` or [morelinq][1].

Bad design? Just Call Add? Missing the obvious?

  [1]: http://code.google.com/p/morelinq/

AddRange to a Collection

Is there a elegant way of obtaining only one `Entry&lt;K,V&gt;` from HashMap, without iterating, if key is not known.

As order of entry of entry is not important, can we say something like

    hashMapObject.get(zeroth_index);

Although I am aware that there exist no such get by index method.

If I tried approach mentioned below, **it would still have to get all the entry set of the hashmap**.

    for(Map.Entry&lt;String, String&gt; entry : MapObj.entrySet()) {
        return entry;
    }

Suggestions are welcome.

EDIT: Please suggest any other Data Structure to suffice requirement.

how to get the one entry from hashmap without iterating

Is there a way to take a List&lt;int&gt; and convert it into a comma separated string?  

I know I can just loop and build it, but somehow I think some of you guys a more cool way of doing it?

I really want to learn these types of &#39;tricks&#39;, so please explain or link to the docs on the method you use.

Converting a List&lt;int&gt; to a comma separated string

I am trying to mimic the functionality of this curl command in Java:

    curl --basic --user username:password -d &quot;&quot; http://ipaddress/test/login

I wrote the following using Commons HttpClient 3.0 but somehow ended up getting an `500 Internal Server Error` from the server. Can someone tell me if I&#39;m doing anything wrong?

   

    public class HttpBasicAuth {
    
    	private static final String ENCODING = &quot;UTF-8&quot;;
    	
    	/**
    	 * @param args
    	 */
    	public static void main(String[] args) {
    		// TODO Auto-generated method stub
    		try {
    
    			HttpClient client = new HttpClient();
    	        
    	        client.getState().setCredentials(
    	                new AuthScope(&quot;ipaddress&quot;, 443, &quot;realm&quot;),
    	                new UsernamePasswordCredentials(&quot;test1&quot;, &quot;test1&quot;)
    	                );
    	        
    	        PostMethod post = new PostMethod(
    	                &quot;http://address/test/login&quot;);
    	        
    	        post.setDoAuthentication( true );
    	        
    	        try {
    	            int status = client.executeMethod( post );
    	            System.out.println(status + &quot;\n&quot; + post.getResponseBodyAsString());
    	        } finally {
    	            // release any connection resources used by the method
    	            post.releaseConnection();
    	        }
    		} catch (Exception e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    	}
       } 

And I later tried a Commons HttpClient 4.0.1 but still the same error:

    import java.io.BufferedReader;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    
    import org.apache.http.HttpEntity;
    import org.apache.http.HttpResponse;
    import org.apache.http.auth.AuthScope;
    import org.apache.http.auth.UsernamePasswordCredentials;
    import org.apache.http.client.ClientProtocolException;
    import org.apache.http.client.methods.HttpPost;
    import org.apache.http.impl.client.DefaultHttpClient;
    
    
    public class HttpBasicAuth {
    
    	private static final String ENCODING = &quot;UTF-8&quot;;
    	
    	/**
    	 * @param args
    	 */
    	public static void main(String[] args) {
    		// TODO Auto-generated method stub
    		
    		try {
    			DefaultHttpClient httpclient = new DefaultHttpClient();
    
    	        httpclient.getCredentialsProvider().setCredentials(
    	                new AuthScope(AuthScope.ANY_HOST, AuthScope.ANY_PORT), 
    	                new UsernamePasswordCredentials(&quot;test1&quot;, &quot;test1&quot;));
    	        
    	        HttpPost httppost = new HttpPost(&quot;http://host:post/test/login&quot;);
    	        
    	        System.out.println(&quot;executing request &quot; + httppost.getRequestLine());
    	        HttpResponse response;
    			response = httpclient.execute(httppost);
    			HttpEntity entity = response.getEntity();
    
    	        System.out.println(&quot;----------------------------------------&quot;);
    	        System.out.println(response.getStatusLine());
    	        if (entity != null) {
    	            System.out.println(&quot;Response content length: &quot; + entity.getContentLength());
    	        }
    	        if (entity != null) {
    	            entity.consumeContent();
    	        }
    
    	        httpclient.getConnectionManager().shutdown();  
    		} catch (ClientProtocolException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		} catch (IOException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    }

Http Basic Authentication in Java using HttpClient?

I&#39;m building a small Java app and hoping to use logback for logging.

My app has a dependency on an older project that does its logging via 

    org.apache.commons | com.springsource.org.apache.commons.logging | 1.1.1

...so my plan was to use 

    org.slf4j | jcl-over-slf4j | 1.5.6

...to redirect the JCL logging to 

    org.slf4j | slf4j-api | 1.6.0

...and ultimately to 

    ch.qos.logback | logback-classic | 0.9.22
    ch.qos.logback | logback-core | 0.9.22

so my app can log through logback via its slf4j API while the old library code can log into the same location via the redirection.

Alas, this results in 

    java.lang.NoSuchMethodError: org.slf4j.spi.LocationAwareLogger.log(Lorg/slf4j/Marker;Ljava/lang/String;ILjava/lang/String;Ljava/lang/Throwable;)V
	at   org.apache.commons.logging.impl.SLF4JLocationAwareLog.info(SLF4JLocationAwareLog.java:141)

I&#39;ve tried higher and lower verision numbers on some of these jars and also digging through API documentation and such... but I&#39;m unable to find and solve the problem. 

Help, please?

Although logback is considered the &quot;strategic&quot; logging framework, I have some leeway in which logging mechanism I ultimately use. I&#39;d hope to use either logback or log4j, though, and I definitely want to merge the old project&#39;s logging into whatever the &quot;new&quot; logging framework ends up being, via a common configuration.

Logging framework incompatibility

How can I convert byte size into a human-readable format in Java?

Like 1024 should become &quot;1 Kb&quot; and 1024*1024 should become &quot;1 Mb&quot;.

I am kind of sick of writing this utility method for each project. Is there a static method in [Apache Commons][1] for this?

  [1]: https://commons.apache.org/


How can I convert byte size into a human-readable format in Java?

Do you use &lt;code&gt;StringUtils.EMPTY&lt;/code&gt; instead of &lt;code&gt;&quot;&quot;&lt;/code&gt;?

I mean either as a return value or if you set a the value of a String variable. I don&#39;t mean for comparison, because there we use &lt;code&gt;StringUtils.isEmpty()&lt;/code&gt;

Content Type	Original Author	Original Content on Stackoverflow
Question	Rakesh Juyal	View Question on Stackoverflow
Solution 1 - Java	skaffman	View Answer on Stackoverflow
Solution 2 - Java	Brian Agnew	View Answer on Stackoverflow
Solution 3 - Java	Dirk	View Answer on Stackoverflow

How to Serialize a list in java?

Java Problem Overview

Java Solutions

Solution 1 - Java

Solution 2 - Java

Solution 3 - Java

Why is XOR used in cryptography?

Committing Machine Specific Configuration Files

Attributions