A Jar file is an Zip archive containing one or multilple java class files. This makes the usage of libraries (consisting of multiple classes) more handy. Directories and Jar files are  added to the classpath and available to the `ClassLoader` at runtime to find particular classes inside of it.

A **JAR** file has many files into it. We generally use .jar files to distribute Java applications or libraries, in the form of Java class files and associated metadata and resources (text, images, etc.). you can say ***JAR =  Java ARchive***.

All java files are compiled into class files and then we use that class file not the .java file. A class is a construct that is used as a blueprint to create instances of the class.

See Wikipedia for more information: [Wikipedia for JAR][1] and [Wikipedia for class][2]


  [1]: http://en.wikipedia.org/wiki/JAR_file
  [2]: http://en.wikipedia.org/wiki/Class_%28computer_programming%29

A java file contains Java code. A Java file is compiled to produce a class file that can be loaded by the JVM. The contents of a class file are rather well explained [here][1]. A Jar file is an archive of otherfile, most likely class files. 


  [1]: http://www.javaworld.com/javaworld/jw-07-1996/jw-07-classfile.html

JAR file is the compressed file format. You can store many files in a JAR file. JAR stands for the Java Archive. This file format is used to distribute a set of java classes. This file helps you to reduce the file size and collect many file in one by compressing files

a Class is explained [here][1]


  [1]: http://download.oracle.com/javase/tutorial/java/concepts/class.html

I have a `ManagedObject class`, and one of the members of the class is a `NSDate`.  I would like to display all objects of the class for which the date is NOT set.  I tried using a predicate like this:

    NSPredicate *predicate = [NSPredicate predicateWithFormat: @&quot;(date = NIL)&quot;];

But I still get objects where the `date` is set.  What is the right way to set up a predicate for this?



How do I set up a NSPredicate to look for objects that have a nil attribute

I did a ctrl K + ctrl C (adds `//` to a line) on a lot of lines of code that I need uncommented. What is the quick key method to uncomment code in Visual studio?

How to uncomment multiple lines of code in Visual Studio

What is the difference between a java class file and a jar file?

Difference between java class and jar

<p>What is the difference between a java class file and a jar file?</p>


Conventional wisdom says you can only throw objects that extend `Throwable` in Java, but is it possible to disable the bytecode verifier and get Java to compile and run code that throws arbitrary objects - or even primitives?

I looked up the JVM&#39;s [`athrow`][1] and it will pop the first objref on the operand stack; but would it check if said reference points to a `Throwable` at run time?


  [1]: http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-6.html#jvms-6.5.athrow

What can you throw in Java?

I would like to get a list of files with a specific extension in a directory. In the API (Java 6), I see a method `File.listFiles(FileFilter)` which would do this.

Since I need a specific extension, I created a `FileNameExtensionFilter`. However I get a compilation error when I use `listFiles` with this. I assumed that since `FileNameExtensionFilter implements FileFilter`, I should be able to do this. Code follows:

    FileNameExtensionFilter filter = new FileNameExtensionFilter(&quot;text only&quot;,&quot;txt&quot;);
    String dir  = &quot;/users/blah/dirname&quot;;
    File f[] = (new File(dir)).listFiles(filter);

The last line shows a compilation error:

&gt; method listFiles(FileNameFilter) in type File is not applicable for arguments of type FileNameExtensionFilter

I am trying to use `listFiles(FileFilter)`, not `listFiles(FileNameFilter)`. Why does the compiler not recognize this?

This works if I write my own extension filter extending `FileFilter`. I would rather use `FileNameExtensionFilter` than write my own. What am I doing wrong?

Using File.listFiles with FileNameExtensionFilter

I have strings with some numbers and english words and I need to translate them to my mother tongue by finding them and replacing them by locallized version of this word. Do you know how to easily achieve replacing words in a string?

Thanks

Edit:

I have tried (part of a string &quot;to&quot; should be replaced by &quot;xyz&quot;):

    string.replace(&quot;to&quot;, &quot;xyz&quot;)

But it is not working...

Android - how to replace part of a string by another string?

I try to add objects to a `List&lt;String&gt;` instance but it throws an `UnsupportedOperationException`.
Does anyone know why?

My Java code:
		
	String[] membersArray = request.getParameterValues(&#39;members&#39;);
	List&lt;String&gt; membersList = Arrays.asList(membersArray);
	
	for (String member : membersList) {
		Person person = Dao.findByName(member);
		List&lt;String&gt; seeAlso;
		seeAlso = person.getSeeAlso();
		if (!seeAlso.contains(groupDn)){
			seeAlso.add(groupDn);
			person.setSeeAlso(seeAlso);
		}
	}
		

The error message:

&lt;pre&gt;
java.lang.UnsupportedOperationException
    java.util.AbstractList.add(Unknown Source)
    java.util.AbstractList.add(Unknown Source)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
&lt;/pre&gt;


Java List.add() UnsupportedOperationException

In my application, I have 2 `LinearLayout`&#39;s right above each other. Via a menu option, I want to be able to make the bottom one disappear, and have the top one drop down over the disappeared `LinearLayout`.

The problem is, I have no idea on how to do this in Java.

It doesn&#39;t have to be animated, I want to hide the `Layout` on return of another activity (the menu), in `OnActivityResult`. The menu `activity` sets a `boolean` on which I check in `OnActivityResult`, and according to it&#39;s value I determine if I need to hide or show the bottom `Layout`:

    // Only change value if it is different from what it was.
    if(mUseVolumeButtonAsPTT != resultData.getBoolean(&quot;UseVolumeButtonAsPTT&quot;)){
    	mUseVolumeButtonAsPTT = resultData.getBoolean(&quot;UseVolumeButtonAsPTT&quot;);
    	if(!mUseVolumeButtonAsPTT){
    		// Hide lower LinearLayout.
    	} else {
    		// Show lower LinearLayout.
    	}
    }

Can anybody give me a hint or a link on how I should do this?

How to hide a View programmatically?

How do I turn a string into a class name, but only if that class already exists?

If Amber is _already_ a class, I can get from a string to the class via:

    Object.const_get(&quot;Amber&quot;)
or (in Rails)

    &quot;Amber&quot;.constantize
But either of these will fail with `NameError: uninitialized constant Amber` if Amber is not already a class.

My first thought is to use the `defined?` method, but it doesn&#39;t discriminate between classes that already exist and those that don&#39;t:

    &gt;&gt; defined?(&quot;Object&quot;.constantize)
    =&gt; &quot;method&quot;
    &gt;&gt; defined?(&quot;AClassNameThatCouldNotPossiblyExist&quot;.constantize)
    =&gt; &quot;method&quot;

So how do I test if a string names a class before I try to convert it?  (Okay, how about a `begin`/`rescue` block to catch NameError errors?  Too ugly?  I agree...)



How do I check if a class is defined?

How can I define a constant inside a class, and make it so it&#39;s visible only when called in a class context?

....something like `Foo::app()-&gt;MYCONSTANT;`

(and if called like `MYCONSTANT` to be ignored)

PHP - define constant inside a class

How to get all methods of a given class A that are decorated with the @decorator2?

    class A():
        def method_a(self):
          pass

        @decorator1
        def method_b(self, b):
          pass

        @decorator2
        def method_c(self, t=5):
          pass

How to get all methods of a python class with given decorator

I have a subclass and I want it to *not* include a class attribute that&#39;s present on the base class.

I tried this, but it doesn&#39;t work:

    &gt;&gt;&gt; class A(object):
    ...     x = 5
    &gt;&gt;&gt; class B(A):
    ...     del x
    Traceback (most recent call last):
      File &quot;&lt;pyshell#1&gt;&quot;, line 1, in &lt;module&gt;
        class B(A):
      File &quot;&lt;pyshell#1&gt;&quot;, line 2, in B
        del x
    NameError: name &#39;x&#39; is not defined

How can I do this?

Python: deleting a class attribute in a subclass

I&#39;m having trouble with this piece of code , after i took this class from the main.cpp file and splitted it in to .h and .cpp the compiler started complaining about the default parameters i was using in a void.

&lt;!-- language: cpp --&gt;

    /* PBASE.H */
        class pBase : public sf::Thread {
    private:
    	bool Running;
    
    public:
    	sf::Mutex Mutex;
    	WORD OriginalColor;
    	pBase(){
    		Launch();
    		Running = true;
    		OriginalColor = 0x7;
    	}
    	void progressBar(int , int);
    	bool key_pressed();
    	void setColor( int );
    	void setTitle( LPCWSTR );
    	bool test_connection(){
    		if(Running == false){
    			return 0;
    		}
    		else{
    			return 1;
    		}
    	return 0;
    	}
    	void Stop(){
    		Running = false;
    		if(Running == false) Wait();
    	}
    };

---

&lt;!-- language: cpp --&gt;

        /* PBASE.CPP */
        
        // ... other stuff above
        
        void pBase::setColor( int _color = -1){
        	if(_color == -1){
        		 SetConsoleTextAttribute( GetStdHandle( STD_OUTPUT_HANDLE ),FOREGROUND_INTENSITY | OriginalColor);
        		 return;
        	}
        	SetConsoleTextAttribute( GetStdHandle( STD_OUTPUT_HANDLE ),FOREGROUND_INTENSITY | _color);
    
    }


And the error , taken from VC2010


&gt; Error	4	error C2572: &#39;pBase::setColor&#39; : redefinition of default parameter : parameter 1


The compiler is complaining about my default parameters?

How do we run a jar file in command prompt?

Run jar file in command prompt

I am currently working on a J2ME polish application, just enhancing it. I am finding difficulties to get the exact version of the jar file.
Is there any way to find the version of the jar file for the imports done in the class? I mean if you have some thing, import x.y.z; can we know the version of the jar x.y package belongs to?

how to check the version of jar file?

What is the difference between a `.jar` and a `.war` file?  
Is it only the file extension or is there something more?

Difference between jar and war in Java

I know this may be a silly question for experienced coders. But I have a library (an http client) that some of the other frameworks/jars used in my project require. But all of them require different major versions like:

    httpclient-v1.jar =&gt; Required by cralwer.jar
    httpclient-v2.jar =&gt; Required by restapi.jar
    httpclient-v3.jar =&gt; required by foobar.jar

Is the classloader intelligent enough to seperate them somehow? Most likely not? How does the Classloader handle this, in case a Class is the same in all three jars. Which one is loaded and why? 

Does the Classloader only pickup exactly one jar or does it mix classes arbitrarily? So for example if a class is loaded from Version-1.jar, all other classes loaded from the same classloader will all go into the same jar? 

How do you handle this problem?

Is there some trick to somehow &quot;incorporate&quot; the jars into the &quot;required.jar&quot; so that the are seen as &quot;one unit/package&quot; by the `Classloader`, or somehow linked?


Java, Classpath, Classloading =&gt; Multiple Versions of the same jar/project

I have a nasty problem referencing resources when using a Maven project and Jar files...

I have all my resources in a dedicated folder /src/main/resources which is part of the build path in Eclipse. Files are referenced using 
&lt;pre&gt;&lt;code&gt;getClass().getResource(&quot;/filename.txt&quot;)
&lt;/code&gt;&lt;/pre&gt;

This works fine in Eclipse but fails in the Jar file - there the resources are located in a folder directly below the jar&#39;s root...

Does anyone know a &#39;best practice&#39; to reference a file both in the JAR and (!) in Eclipse?

&lt;b&gt;Edit:&lt;/b&gt;
The problem is that while the resources actually are located in the JAR in a folder &quot;resources&quot; at the top level, the above method fails to find the file...

Content Type	Original Author	Original Content on Stackoverflow
Question	hari	View Question on Stackoverflow
Solution 1 - Java	BertNase	View Answer on Stackoverflow
Solution 2 - Java	Harry Joy	View Answer on Stackoverflow
Solution 3 - Java	Nirmal- thInk beYond	View Answer on Stackoverflow
Solution 4 - Java	CloudyMarble	View Answer on Stackoverflow

Difference between java class and jar

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How to uncomment multiple lines of code in Visual Studio

How do I set up a NSPredicate to look for objects that have a nil attribute

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