The Java language specification uses this explicit language:

&gt; @return an array containing the constants of this enum type, in the order they&#39;re declared [&lt;sup&gt;[Source]&lt;/sup&gt;][1]

So, yes, they will be returned in declaration order. It&#39;s worth noting that the order might change over time if someone changes the class so be very careful about how you use this.


  [1]: http://docs.oracle.com/javase/specs/jls/se6/html/classes.html#8.9

Yes, it is a guaranteed to return them in that order.

However you should avoid relying on that, and on the `ordinal()` value, since it can change after inserting new items, for example.

It is determined by the order your values are declared in. However, **there is no guarantee that you (or someone else) won&#39;t reorder / insert / remove values in the future**. So you shouldn&#39;t rely on the order.

Effective Java 2nd. Edition dedicates its Item 31 to a closely related topic: **Use instance fields instead of ordinals**:

&gt; Never derive a value associated with an enum from its ordinal; store it in an instance field instead.


The other answers are good, but don&#39;t comment on this: 

&gt; &quot;Is it a rule or it is not guaranteed to be not changed in the next
&gt; Jdk releases?&quot;

 I don&#39;t believe that guarantees on future JDKs exist, so you shouldn&#39;t even worry about them. There would be no way to enforce them, future JDK leads might just decide to reneg on such guarantees. It&#39;s like the Westminster system of parliament: &quot;No Parliament can bind a future parliament.&quot;

That said, the history of the JDK reveals excellent consistency. They don&#39;t make a lot of breaking changes, so you can be pretty confident that current **specified** (not just observed) behaviour will be preserved.

I like using question mark at the end of method/function names in other languages. Java doesn&#39;t let me do this. As a workaround how else can I name boolean returning methods in Java? Using an `is`, `has`, `should`, `can` in the front of a method sound okay for some cases. Is there a better way to name such methods?

For e.g. createFreshSnapshot? 






Naming conventions for Java methods that return boolean

I have to open a file-like object in python (it&#39;s a serial connection through /dev/) and then close it. This is done several times in several methods of my class. How I WAS doing it was opening the file in the constructor, and then closing it in the destructor. I&#39;m getting weird errors though and I think it has to do with the garbage collector and such, I&#39;m still not used to not knowing exactly when my objects are being deleted =\

The reason I was doing this is because I have to use `tcsetattr` with a bunch of parameters each time I open it and it gets annoying doing all that all over the place. So I want to implement an inner class to handle all that so I can use it doing  
`with Meter(&#39;/dev/ttyS2&#39;) as m:`

I was looking online and I couldn&#39;t find a really good answer on how the `with` syntax is implemented. I saw that it uses the `__enter__(self)` and `__exit(self)__` methods. But is all I have to do implement those methods and I can use the with syntax? Or is there more to it?

Is there either an example on how to do this or some documentation on how it&#39;s implemented on file objects already that I can look at?

Implementing use of &#39;with object() as f&#39; in custom class in python

I have a enum `SOME_ENUM`: 

    public enum SOME_ENUM {
      EN_ONE,
      EN_TWO,
      EN_THREE;
    }

Will `SOME_ENUM.values()` always return the enums in the order of enum declarations:
`EN_ONE, EN_TWO, EN_THREE`? Is it a rule or it is not guaranteed to be not changed in the next JDK releases? 

enum.values() - is an order of returned enums deterministic

I have a enum <code>SOME_ENUM</code>:
<pre><code class="hljs language-arduino">public enum SOME_ENUM {
 EN_ONE,
 EN_TWO,
 EN_THREE;
}
</code></pre>
Will <code>SOME_ENUM.values()</code> always return the enums in the order of enum declarations:
<code>EN_ONE, EN_TWO, EN_THREE</code>? Is it a rule or it is not guaranteed to be not changed in the next JDK releases?

I have a database with the following structure:

    CREATE TABLE entity (
        id SERIAL,
        name VARCHAR(255),
        PRIMARY KEY (id)
    );
    
    CREATE TABLE entity_property (
        entity_id SERIAL,
        name VARCHAR(255),
        value TEXT
    );

When I try to create an EntityProperty class

    @Entity
    @Table(name=&quot;entity_property&quot;)
    public class EntityProperty {
    
        private String name;
        private String value;
    
        @Column(name=&quot;name&quot;)
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
    
        @Column(name=&quot;value&quot;, nullable=true, length=255)
        public String getValue() {
            return value;
        }
        public void setValue(String value) {
            this.value = value;
        }
    }

I get the following exception:

    org.hibernate.AnnotationException: No identifier specified for entity: package.EntityProperty

I know that JPA entities must have a primary key but I can&#39;t change the database schema due to reasons that are beyond my control. Is it possible to create JPA (Hibernate) entities that will work with database schema like this? 



JPA entity without id

I am starting to look into Enterprise Java and the book I am following mentions that it will use JBoss. Netbeans ships with Glassfish. I have used Tomcat in the past.

What are the differences between these three programs?

What is the difference between Tomcat, JBoss and Glassfish?

This code just made me stare at my screen for a few minutes:

    loop:
    for (;;) {
        // ...
    }

([line 137 here][1])

I have never seen this before, and I had no idea Java has a &quot;loop&quot; keyword (NetBeans doesn&#39;t even color it like a keyword), and it does compile fine with JDK 6.

What is the explanation?

  [1]: http://bazaar.launchpad.net/~play-developers/play/1.0/annotate/head:/framework/src/play/templates/TemplateCompiler.java#L137



&quot;loop:&quot; in Java code. What is this, and why does it compile?

Recalling this [post enumerating several problems of using singletons][1]
and having seen several examples of Android applications using singleton pattern, I wonder if it&#39;s a good idea to use Singletons instead of single instances shared through global application state (subclassing android.os.Application and obtaining it through context.getApplication()).

What advantages/drawbacks would both mechanisms have?

To be honest, I expect the same answer in this post https://stackoverflow.com/questions/2709071/singleton-pattern-with-web-application-not-a-good-idea but applied to Android. Am I correct? What&#39;s different in DalvikVM otherwise?

EDIT: I would like to have opinions on several aspects involved:

- Synchronization
- Reusability
- Testing


  [1]: http://www.antonioshome.net/blog/2006/20060906-1.php

Singletons vs. Application Context in Android?

So, I am working on this class that has a few static constants:

    public abstract class Foo {
        ...
        public static final int BAR;
        public static final int BAZ;
        public static final int BAM;
        ...
    }

Then, I would like a way to get a relevant string based on the constant:

    public static String lookup(int constant) {
        switch (constant) {
            case Foo.BAR: return &quot;bar&quot;;
            case Foo.BAZ: return &quot;baz&quot;;
            case Foo.BAM: return &quot;bam&quot;;
            default: return &quot;unknown&quot;;
        }
    }

However, when I compile, I get a `constant expression required` error on each of the 3 case labels.

I understand that the compiler needs the expression to be known at compile time to compile a switch, but why isn&#39;t `Foo.BA_` constant?

Java switch statement: Constant expression required, but it IS constant

How can I get the name of a Java Enum type given its value?

I have the following code which works for a **particular** Enum type, can I make it more **generic**?

	public enum Category {

        APPLE(&quot;3&quot;), 
        ORANGE(&quot;1&quot;), 

		private final String identifier;

        private Category(String identifier) {
		    this.identifier = identifier;
		}

		public String toString() {
			return identifier;
		}
		 
		public static String getEnumNameForValue(Object value){
            Category[] values = Category.values();
		    String enumValue = null;
		    for(Category eachValue : values) {
		        enumValue = eachValue.toString();

		        if (enumValue.equalsIgnoreCase(value)) {
		            return eachValue.name();
                }
		    }
            return enumValue;
        }
	}



Java getting the Enum name given the Enum Value

This is a valid enum

    public enum myEnum
    {
      a= 1,
      b= 2,
      c= 3,
      d= 4,
      e= 5,
      f= 6,
      g= 7,
      h= 0xff
    };

But this is not

    public enum myEnum
    {
      1a = 1,
      2a = 2,
      3a = 3,
    };

Is there a way I can use an number in a enum?  I already have code that would populate dropdowns from enums so it would be quite handy



C# using numbers in an enum

What is the best way to have a `enum` type represent a set of strings?

I tried this:

    enum Strings{
       STRING_ONE(&quot;ONE&quot;), STRING_TWO(&quot;TWO&quot;)
    }

How can I then use them as `Strings`?


Best way to create enum of strings?

I&#39;m currently creating integer constants in the following manner.

    public class Constants {
	    public static int SIGN_CREATE=0;
	    public static int SIGN_CREATE=1;
	    public static int HOME_SCREEN=2;
	    public static int REGISTER_SCREEN=3;
    }

When i try to do this in enum manner 

    public enum PAGE{SIGN_CREATE,SIGN_CREATE,HOME_SCREEN,REGISTER_SCREEN}

and When i used `PAGE.SIGN_CREATE` it should return 1;

Storing integer values as constants in Enum manner in java

Is there a generic way to cast `int` to `enum` in `C++`?

If `int` falls in range of an `enum` it should return an `enum` value, otherwise throw  an `exception`. Is there a way to write it *generically*? More than one `enum type` should be supported.

Background: I have an external **enum** type and *no control* over the source code. I&#39;d like to store this value in a database and retrieve it.

Generic way to cast int to enum in C++

As far as I know, `private` is the default *everywhere* in C# (meaning that if I don&#39;t write `public`, `protected`, `internal`, etc. it will be `private` by default). (Please correct me if I am wrong.)

So, what&#39;s the reason to write that keyword, or why does it even exist for members?

For example, when an event handler is auto-generated it looks like this:

    private void RatTrap_MouseEnter(object sender, CheeseEventArgs e)
    {
        
    }

But why does it even write private if that&#39;s implied and default? Just so that novice developers (who don&#39;t know it&#39;s the C# default) know that it&#39;s private? Or is there a difference for the compiler?

Moreover, is there a case where writing &quot;private&quot; (alone) *will* change the accessibility of the member?


Any reason to write the &quot;private&quot; keyword in C#?

I wish HTML could do something semantically equivalent to this;

    &lt;dl class=&quot;main-list&quot;&gt;
        &lt;definitionitem&gt;
            &lt;dt&gt;Some Thing&lt;/dt&gt;
                &lt;dd&gt;You know it!&lt;/dd&gt;
            &lt;dt&gt;Another Thing&lt;/dt&gt;
                &lt;dd&gt;Word.&lt;/dd&gt;
        &lt;/definitionitem&gt;
        &lt;definitionitem&gt;
            &lt;dt&gt;Stuff&lt;/dt&gt;
                &lt;dd&gt;Alright!&lt;/dd&gt;
        &lt;/definitionitem&gt;
    &lt;/dl&gt;

However, since the closest I&#39;ve come is something I&#39;m not 100% satisfied with the semantics of;

    &lt;div class=&quot;redundant-wrapper&quot;&gt;
        &lt;dl class=&quot;main-list&quot;&gt;
            &lt;dt&gt;Some Thing&lt;/dt&gt;
                &lt;dd&gt;You know it!&lt;/dd&gt;
            &lt;dt&gt;Another Thing&lt;/dt&gt;
                &lt;dd&gt;Word.&lt;/dd&gt;
        &lt;/dl&gt;
        &lt;dl class=&quot;another-main-list&quot;&gt;
            &lt;dt&gt;Stuff!&lt;/dt&gt;
                &lt;dd&gt;Alright!&lt;/dd&gt;
        &lt;/dl&gt;
    &lt;/div&gt;

I was wondering if anyone has any other ideas of how you might do this?

Also, the reason the items would be grouped is because they are visually grouped in the content that is being marked up. Imagine a dictionary page, with a single definition list, where each definition is in an inset box that is floated left. I run into this situation all the time.

Is there a valid way to wrap a dt and a dd with an HTML element?

I want to code an application that can read and decode a pdf document; now where I&#39;m supposed to get the specs for this fileformat ? The PDF format is standardized from the ISO group but it&#39;s not clear to me where is the most reliable source for getting this kind of informations.

what is a good source to start with this file format ?

PDF specifications for coders: Adobe or ISO?

I get it on some level, but I have yet to see an example that didn&#39;t bring up more questions than answers.

http://rhnh.net/2011/01/31/yaml-tutorial

    # Set.new([1,2]).to_yaml
    --- !ruby/object:Set 
    hash: 
      1: true
      2: true


I get that we&#39;re declaring a Set tag.  I don&#39;t get what the subsequent hash mapping has to do with it.  Are we declaring a schema?  Can someone show me an example with multiple tag declarations?


I&#39;ve read through the spec: http://yaml.org/spec/1.2/spec.html#id2761292

    %TAG ! tag:clarkevans.com,2002:

Is this declaring a schema?  Is there something else a parser has to do in order to successfully parse the file?  A schema file of some type?

http://www.yaml.org/refcard.html

    Tag property: # Usually unspecified.
        none    : Unspecified tag (automatically resolved by application).
        &#39;!&#39;     : Non-specific tag (by default, &quot;!!map&quot;/&quot;!!seq&quot;/&quot;!!str&quot;).
        &#39;!foo&#39;  : Primary (by convention, means a local &quot;!foo&quot; tag).
        &#39;!!foo&#39; : Secondary (by convention, means &quot;tag:yaml.org,2002:foo&quot;).
        &#39;!h!foo&#39;: Requires &quot;%TAG !h! &lt;prefix&gt;&quot; (and then means &quot;&lt;prefix&gt;foo&quot;).
        &#39;!&lt;foo&gt;&#39;: Verbatim tag (always means &quot;foo&quot;).

Why is it relevant to have a primary and secondary tag, and why does a secondary tag refer to a URI?  What problem is being solved by having these?

I seem to see a lot of &quot;what they are&quot;, and no &quot;why are they there&quot;, or &quot;what are they used for&quot;.

I don&#39;t understand what a YAML tag is

As the subject asks; do UNIX timestamps change in each timezone?

**For example,** if I sent a request to another email the other side of the world saying, **&quot;Send out an email when the time is 1397484936&quot;**, would the other server&#39;s timestamp be 12 hours behind my own?

Content Type	Original Author	Original Content on Stackoverflow
Question	Skarab	View Question on Stackoverflow
Solution 1 - Java	GaryF	View Answer on Stackoverflow
Solution 2 - Java	Bozho	View Answer on Stackoverflow
Solution 3 - Java	Péter Török	View Answer on Stackoverflow
Solution 4 - Java	Fletch	View Answer on Stackoverflow

enum.values() - is an order of returned enums deterministic

Java Problem Overview

Java Solutions

Solution 1 - Java

Solution 2 - Java

Solution 3 - Java

Solution 4 - Java

Implementing use of 'with object() as f' in custom class in python

Naming conventions for Java methods that return boolean

Attributions