The `String` object is immutable but what it is is actually a reference to a `String` object which could be changed.

For example:

    String someString = &quot;Lala&quot;;

You can reassign the value held by this variable (to make it reference a different string):

    someString = &quot;asdf&quot;;

However, with this:

    final String someString = &quot;Lala&quot;;

Then the above reassignment would not be possible and would result in a compile-time error.

`final` refers to the variable, not the object, so yes, it make sense.

e.g.

    final String s = &quot;s&quot;;
    s = &quot;a&quot;; // illegal

It makes sense. The `final` keyword prevents future assignments to the variable. The following would be an error in java:

    final String x = &quot;foo&quot;;
    x = &quot;bar&quot; // error on this assignment

References are final, Objects are not. You can define a mutable object as final and change state of it. What final ensures is that the reference you are using cannot ever point to another object again.

Can I initialize an STL vector with 10 of the same integer in an initializer list?  My attempts so far have failed me.

Can I initialize an STL vector with 10 of the same integer in an initializer list?

I&#39;m need to check if `memory_limit` is at least `64M` in my script installer. This is just part of PHP code that should work, but probably due to this &quot;M&quot; it&#39;s not reading properly the value. How to fix this ?

      //memory_limit
        echo &quot;&lt;phpmem&gt;&quot;;
        if(key_exists(&#39;PHP Core&#39;, $phpinfo))
        {
            if(key_exists(&#39;memory_limit&#39;, $phpinfo[&#39;PHP Core&#39;]))
            {
                $t=explode(&quot;.&quot;, $phpinfo[&#39;PHP Core&#39;][&#39;memory_limit&#39;]);
                if($t[0]&gt;=64)
                    $ok=1;
                else
                    $ok=0;
                echo &quot;&lt;val&gt;{$phpinfo[&#39;PHP Core&#39;][&#39;memory_limit&#39;]}&lt;/val&gt;&lt;ok&gt;$ok&lt;/ok&gt;&quot;;
            }
            else
               echo &quot;&lt;val&gt;&lt;/val&gt;&lt;ok&gt;0&lt;/ok&gt;&quot;;
        }
        else
            echo &quot;&lt;val&gt;&lt;/val&gt;&lt;ok&gt;0&lt;/ok&gt;&quot;;
        echo &quot;&lt;/phpmem&gt;\n&quot;; 

checking memory_limit in PHP

&gt; **Possible Duplicate:**  
&gt; [String and Final](https://stackoverflow.com/questions/874978/string-and-final)  

&lt;!-- End of automatically inserted text --&gt;

From [http://docs.oracle.com/javase/6/docs/api/java/lang/String.html][1] I can read that:

    Strings are constant; their values cannot be changed after they are created. 

Does this mean that a `final String` does not really make sense in Java, in the sense that the `final` attribute is somehow redundant?


  [1]: http://docs.oracle.com/javase/6/docs/api/java/lang/String.html

Does it make sense to define a final String in Java?

> Possible Duplicate: 
> <a href="https://stackoverflow.com/questions/874978/string-and-final" target="_blank" rel="noopener noreferrer">String and Final</a>

From <a href="http://docs.oracle.com/javase/6/docs/api/java/lang/String.html" target="_blank" rel="noopener noreferrer">http://docs.oracle.com/javase/6/docs/api/java/lang/String.html</a> I can read that:
<pre><code class="hljs language-ini">Strings are constant; their values cannot be changed after they are created. 
</code></pre>
Does this mean that a <code>final String</code> does not really make sense in Java, in the sense that the <code>final</code> attribute is somehow redundant?

I need to change the following `if`&#39;s to a `switch`-`case` while checking for a `String`, to improve the cyclomatic complexity.

    String value = some methodx;
    if (&quot;apple&quot;.equals(value)) {
        method1;
    }

    if (&quot;carrot&quot;.equals(value)) {
        method2;
    }

    if (&quot;mango&quot;.equals(value)) {
        method3;
    }

    if (&quot;orange&quot;.equals(value)) {
        method4;
    }

But I am not sure what value I&#39;m going to get.

Use string in switch case in java

I am running into some issues with the Java socket API. I am trying to display the number of players currently connected to my game.  It is easy to determine when a player has connected.  However, it seems unnecessarily difficult to determine when a player has disconnected using the socket API.

Calling `isConnected()` on a socket that has been disconnected remotely always seems to return `true`.  Similarly, calling `isClosed()` on a socket that has been closed remotely always seems to return `false`.  I have read that to actually determine whether or not a socket has been closed, data must be written to the output stream and an exception must be caught.  This seems like a really unclean way to handle this situation.  We would just constantly have to spam a garbage message over the network to ever know when a socket had closed.

Is there any other solution?

Java socket API: How to tell if a connection has been closed?

Is there a short and sweet way to generate a `List&lt;Integer&gt;`, or perhaps an  `Integer[]` or `int[]`, with sequential values from some `start` value to an `end` value?

That is, something shorter than, but equivalent to&lt;sup&gt;1&lt;/sup&gt; the following:

    void List&lt;Integer&gt; makeSequence(int begin, int end) {
      List&lt;Integer&gt; ret = new ArrayList&lt;&gt;(end - begin + 1);
      for (int i=begin; i&lt;=end; i++) {
        ret.add(i);
      }
      return ret;  
    }

The use of guava is fine.

**Update:**

## Performance Analysis

Since this question has received several good answers, both using native Java 8 and third party libraries, I thought I&#39;d test the performance of all the solutions.

The first test simply tests creating a list of 10 elements `[1..10]` using the following methods:

 - **classicArrayList**: the code given above in my question (and essentially the same as adarshr&#39;s answer).
 - **eclipseCollections**: the code given in [Donald&#39;s answer](https://stackoverflow.com/a/36350104/149138) below using Eclipse Collections 8.0.
 - **guavaRange**: the code given in [daveb&#39;s answer](https://stackoverflow.com/a/10242491/149138) below. Technically, this doesn&#39;t create a `List&lt;Integer&gt;` but rather a `ContiguousSet&lt;Integer&gt;` - but since it implements `Iterable&lt;Integer&gt;` in-order, it mostly works for my purposes.
 - **intStreamRange**: the code given in [Vladimir&#39;s answer](https://stackoverflow.com/a/22829036/149138) below, which uses `IntStream.rangeClosed()` - which was introduced in Java 8.
 - **streamIterate**: the code given in [Catalin&#39;s answer](https://stackoverflow.com/a/36114723/149138) below which also uses `IntStream` functionality introduced in Java 8.

Here are the results in kilo-operations per second (higher numbers are better), for all the above with lists of size 10:

[![List creation throughput][1]][1]

... and again for lists of size 10,000:

[![enter image description here][2]][2]

That last chart is correct - the solutions other than Eclipse and Guava are too slow to even get a single pixel bar! The fast solutions are 10,000 to 20,000 _times_ faster than the rest.

What&#39;s going on here, of course, is that the guava and eclipse solutions don&#39;t actually materialize any kind of 10,000 element list - they are simply fixed-size wrappers around the start and endpoints. Each element is created as needed during iteration. Since we don&#39;t actually iterate in this test, the cost is deferred. All of the other solutions actually materialize the full list in memory and pay a heavy price in a creation-only benchmark.

Let&#39;s do something a bit more realistic and also iterate over all the integers, summing them. So in the case of the `IntStream.rangeClosed` variant, the benchmark looks like:

	@Benchmark
	public int intStreamRange() {
		List&lt;Integer&gt; ret = IntStream.rangeClosed(begin, end).boxed().collect(Collectors.toList());  
		
		int total = 0;
		for (int i : ret) {
			total += i;
		}
		return total;  
	}

Here, the pictures changes a lot, although the non-materializing solutions are still the fastest. Here&#39;s length=10:

[![List&lt;Integer&gt; Iteration (length=10)][3]][3] 

... and length = 10,000:

[![List&lt;Integer&gt; Iteration (length=10,000)][4]][4]

The long iteration over many elements evens things up a lot, but eclipse and guava remain more than twice as fast even on the 10,000 element test.

So if you _really_ want a `List&lt;Integer&gt;`, eclipse collections seems like the best choice - but of course if you use streams in a more native way (e.g., forgetting `.boxed()` and doing a reduction in the primitive domain) you&#39;ll probably end up faster than all these variants. 

---

&lt;sup&gt;1&lt;/sup&gt; Perhaps with the exception of error handling, e.g., if `end` &lt; `begin`, or if the size exceeds some implementation or JVM limits (e.g., arrays larger than `2^31-1`.


  [1]: https://i.stack.imgur.com/j830l.png
  [2]: https://i.stack.imgur.com/zdxOz.png
  [3]: https://i.stack.imgur.com/VQDYA.png
  [4]: https://i.stack.imgur.com/LWWtu.png

How can I generate a list or array of sequential integers in Java?

When I make my own Android custom class, I `extend` its native class. Then when I want to override the base method, I always call `super()` method, just like I always do in `onCreate`, `onStop`, etc.

And I thought this is it, as from the very beginning Android team advised us to always call `super` on every method override.

But, in **many books** I can see that developers, more experienced than myself, often omit calling `super` and I really doubt they do it as a lack of knowledge. For example, look at this basic [SAX][1] parser class where `super` is omitted in `startElement`, `characters` and `endElement`:

    public class SAXParser extends DefaultHandler{
        public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
            if(qName.equalsIgnoreCase(&quot;XXY&quot;)) {
                //do something
            }
        }

        public void characters(char[] ch, int start, int length) throws SAXException {
            //do something
        }

        public void endElement(String uri, String localName, String qName) throws SAXException {
            if(qName.equalsIgnoreCase(&quot;XXY&quot;)) {
                //do something
            }else () {
                //do something
            }
        }
    }

If you try to create any override method via Eclipse or any other IDE, `super` will always be created as a part of automated process.

This was just a simple example. Books are **full of similar code**.

How do they know when you must call `super` and when you can omit it calling?

PS. Do not bind to this specific example. It was just an example randomly picked from many examples.

(This may sound like a beginner question, but I am really confused.)

  [1]: http://en.wikipedia.org/wiki/Simple_API_for_XML


When NOT to call super() method when overriding?

I have an image which I resize:

    if((width != null) || (height != null))
    {
        try{
            // scale image on disk
            BufferedImage originalImage = ImageIO.read(file);
            int type = originalImage.getType() == 0? BufferedImage.TYPE_INT_ARGB
                                                   : originalImage.getType();

            BufferedImage resizeImageJpg = resizeImage(originalImage, type, 200, 200);
            ImageIO.write(resizeImageJpg, &quot;jpg&quot;, file); 

           } catch(IOException e) {
               System.out.println(e.getMessage());
           }
    }

This is how I resize the image:

    private static BufferedImage resizeImage(BufferedImage originalImage, int type,
                                             Integer img_width, Integer img_height)
    {
        BufferedImage resizedImage = new BufferedImage(img_width, img_height, type);
        Graphics2D g = resizedImage.createGraphics();
        g.drawImage(originalImage, 0, 0, img_width, img_height, null);
        g.dispose();

        return resizedImage;
    }

Now the problem is, I also need to maintain aspect ratio. That is, I need the new 200/200 image to contain the new image scaled. Something like this:
![enter image description here][1]

I tried some things but they didn&#39;t work out as expected.
Any help is appreciated. Thanks alot.

  [1]: http://i.stack.imgur.com/ZoXYs.jpg


Java image resize, maintain aspect ratio

&gt; **Possible Duplicate:**  
&gt; [How do I treat an ASCII string as unicode and unescape the escaped characters in it in python?](https://stackoverflow.com/questions/267436/how-do-i-treat-an-ascii-string-as-unicode-and-unescape-the-escaped-characters-in)  
&gt; [How do convert unicode escape sequences to unicode characters in a python string](https://stackoverflow.com/questions/990169/how-do-convert-unicode-escape-sequences-to-unicode-characters-in-a-python-string)  

&lt;!-- End of automatically inserted text --&gt;

I have a string that contains unicode characters e.g. `\u2026` etc. Somehow it is not received to me as `unicode`, but is received as a `str`. How do I convert it back to unicode?

    &gt;&gt;&gt; a=&quot;Hello\u2026&quot;
    &gt;&gt;&gt; b=u&quot;Hello\u2026&quot;
    &gt;&gt;&gt; print a
    Hello\u2026
    &gt;&gt;&gt; print b
    Hello…
    &gt;&gt;&gt; print unicode(a)
    Hello\u2026
    &gt;&gt;&gt; 

So clearly `unicode(a)` is not the answer. Then what is?


Python string to unicode

I have a list of strings like this:

    [&#39;Aden&#39;, &#39;abel&#39;]

I want to sort the items, case-insensitive.
So I want to get:

    [&#39;abel&#39;, &#39;Aden&#39;]

But I get the opposite with `sorted()` or `list.sort()`, because uppercase appears before lowercase.

How can I ignore the case? I&#39;ve seen solutions which involves lowercasing all list items, but I don&#39;t want to change the case of the list items.



case-insensitive list sorting, without lowercasing the result?

I didn&#39;t get an optimized regex that split me a String basing into the first white space occurrence:

    var str=&quot;72 tocirah sneab&quot;;

I need to get:

    [
        &quot;72&quot;,
        &quot;tocirah sneab&quot;,
    ]

Split string on the first white space occurrence

How do I append a single char to a string in C?

i.e 
 
    char* str = &quot;blablabla&quot;;
    char c = &#39;H&#39;;
    str_append(str,c); /* blablablaH */
 

Append Char To String in C?

Which advantages/disadvantages we can get by making ArrayList (or other Collection) final? I still can add to ArrayList new elements, remove elements and update it. But what is effect making it&#39;s final? 

what is the sense of final ArrayList?

Consider the following Java class declaration:

    public class Test {
    
        private final int defaultValue = 10;
        private int var;
        
        public Test() {
            this(defaultValue);    // &lt;-- Compiler error: cannot reference defaultValue before supertype constructor has been called.
        }
        
        public Test(int i) {
            var = i;
        }
    }

The code will not compile, with the compiler complaining about the line I&#39;ve highlighted above. Why is this error happening and what&#39;s the best workaround?

Cannot reference &quot;X&quot; before supertype constructor has been called, where x is a final variable

I found a code where it declared code like

    private final static String API_RTN_SUCCESS = &quot;0&quot;;
    private final static String API_RTN_ERROR = &quot;1&quot;;

    public static final String SHARED_PREFERENCE_CONFIG = &quot;shared_preference_config&quot;;
    public static final String STARTUP_SETTING_KEY = &quot;startup_setting&quot;;

What is the difference between them or are they same? Or does it differ for `private` or `public`?

Difference between final static and static final

I have seen much code where people write `public static final String mystring = ...`
and then just use a value.

Why do they have to do that? Why do they have to initialize the value as `final` prior to using it?

**UPDATE**

Ok, thanks all for all your answers, I understand the meaning of those key (public static final). What I dont understand is why people use that even if the constant will be used only in one place and only in the same class. why declaring it? why dont we just use the variable? 


when exactly are we supposed to use &quot;public static final String&quot;?

[Wikipedia](http://en.wikipedia.org/wiki/C%2B%2B11#Explicit_overrides_and_final) has the following example on the C++11 final modifier:

    struct Base2 {
        virtual void f() final;
    };
     
    struct Derived2 : Base2 {
        void f(); // ill-formed because the virtual function Base2::f has been marked final
    };

I don&#39;t understand the point of introducing a virtual function and immediately marking it as final. Is this simply a bad example, or is there more to it?

Content Type	Original Author	Original Content on Stackoverflow
Question	Campa	View Question on Stackoverflow
Solution 1 - Java	Mike Kwan	View Answer on Stackoverflow
Solution 2 - Java	MByD	View Answer on Stackoverflow
Solution 3 - Java	Colin D	View Answer on Stackoverflow
Solution 4 - Java	Kalpak Gadre	View Answer on Stackoverflow

Does it make sense to define a final String in Java?

Java Problem Overview

Java Solutions

Solution 1 - Java

Solution 2 - Java

Solution 3 - Java

Solution 4 - Java

checking memory_limit in PHP

Can I initialize an STL vector with 10 of the same integer in an initializer list?

Attributions