[`LinkedHashMap`][1] is precisely what you&#39;re looking for.

It is exactly like `HashMap`, except that when you iterate over it, it presents the items in the insertion order.


  [1]: http://docs.oracle.com/javase/6/docs/api/java/util/LinkedHashMap.html

[`HashMap`][1] is unordered per the second line of the documentation:

&gt; This class makes no guarantees as to the order of the map; in particular, it does not guarantee that the order will remain constant over time.

Perhaps you can do as aix suggests and use a `LinkedHashMap`, or another ordered collection. Take a look on javapractices.com&#39;s guide on [Choosing the right Collection][2].


  [1]: http://docs.oracle.com/javase/6/docs/api/java/util/HashMap.html
  [2]: http://www.javapractices.com/topic/TopicAction.do?Id=65

A few months ago I tattooed a [fork bomb][1] on my arm, and I skipped the whitespaces, because I think it looks nicer without them. But to my dismay, **sometimes** (not always) when I run it in a shell it doesn&#39;t start a fork bomb, but it just gives a syntax error. 

    bash: syntax error near unexpected token `{:&#39;

Yesterday it happened when I tried to run it in a friend&#39;s [Bash][2] shell, and then I added the whitespace and it suddenly worked, `:(){ :|:&amp; };:` instead of `:(){:|:&amp;};:`

Does the whitespace matter; have I tattooed a syntax error on my arm?!

It seems to always work in [zsh][3], but not in Bash.

[A related question][4] does not explain anything about the whitespaces, which really is my question; **Why is the whitespace needed for Bash to be able to parse it correctly?**


  [1]: http://en.wikipedia.org/wiki/Fork_bomb
  [2]: http://en.wikipedia.org/wiki/Bash_%28Unix_shell%29
  [3]: http://en.wikipedia.org/wiki/Z_shell
  [4]: https://stackoverflow.com/questions/991142/how-does-this-bash-fork-bomb-work
  [5]: http://i.stack.imgur.com/2ujMh.jpg


Why is whitespace sometimes needed around metacharacters?

I&#39;m developing an application which displays images, and plays sounds from a database. I&#39;m trying to decide whether or not to use a separate JFrame to add images to the database from the GUI. 

I&#39;m just wondering whether it is good practice to use multiple JFrame windows?

The Use of Multiple JFrames: Good or Bad Practice?

I&#39;m using a `HashMap`. When I iterate over the map, the data is returned in (often the same) random order. But the data was inserted in a specific order, and I need to preserve the insertion order. How can I do this?

How to preserve insertion order in HashMap?

<p>I'm using a <code>HashMap</code>. When I iterate over the map, the data is returned in (often the same) random order. But the data was inserted in a specific order, and I need to preserve the insertion order. How can I do this?</p>


I have an `ArrayList` suppose `list`, and it has 8 items A-H and now I want to delete 1,3,5 position Item stored in int array from the `list` how can I do this.

I am trying to do this with 

    ArrayList&lt;String&gt; list = new ArrayList&lt;String&gt;();
    list.add(&quot;A&quot;);
    list.add(&quot;B&quot;);
    list.add(&quot;C&quot;);
    list.add(&quot;D&quot;);
    list.add(&quot;E&quot;);
    list.add(&quot;F&quot;);
    list.add(&quot;G&quot;);
    list.add(&quot;H&quot;);
    				
    int i[] = {1,3,5};
    				
    for (int j = 0; j &lt; i.length; j++) {
        list.remove(i[j]);
    }

But after first item deleted positioned of array is changed and in the next iterate it deletes wrong element or give exception. 

Remove Item from ArrayList

Which of the following ways is an efficient way of determining substring containment?

    if (str.indexOf(&quot;/&quot;) &gt; -1)

or
 
    if (str.contains(&quot;/&quot;)) 






Which String method: &quot;contains&quot; or &quot;indexOf &gt; -1&quot;?

I have a web application to test with Selenium. There is a lot of JavaScript running on page load.  
This JavaScript code is not so well written but I can&#39;t change anything.
So waiting for an element to appear in the DOM with `findElement()` method is not an option.   
I want to create a generic function in Java to wait for a page to load, a possible solution would be:  

 - run a JavaScript script form WebDriver and store the result of `document.body.innerHTML` in a string variable `body`.
 - compare the `body` variable to the previous version of `body`. if they are the same then set increment a counter `notChangedCount` otherwise set `notChangedCount` to zero.
 - wait for a litte time (50 ms for example).
 - if the page has not changed for some time (500 ms for example) so `notChangedCount &gt;= 10` then exit the loop otherwise loop to the first step.
  

Do you think it&#39;s a valid solution?


Selenium WebDriver: Wait for complex page with JavaScript to load

I am studying overriding member functions in JAVA and thought about experimenting with overriding member variables.

So, I defined classes

    public class A{
        public int intVal = 1;
        public void identifyClass()
        {
            System.out.println(&quot;I am class A&quot;);
        }
    }

    public class B extends A
    {
        public int intVal = 2;
        public void identifyClass()
        {
            System.out.println(&quot;I am class B&quot;);
        }
    }

    public class mainClass
    {
        public static void main(String [] args)
        {
            A a = new A();
            B b = new B();
            A aRef;
            aRef = a;
            System.out.println(aRef.intVal);
            aRef.identifyClass();
            aRef = b;
            System.out.println(aRef.intVal);
            aRef.identifyClass();
        }
    }

The output is:

    1
    I am class A
    1
    I am class B



I am not able to understand why when aRef is set to b intVal is still of class A?


Overriding member variables in Java ( Variable Hiding)

I&#39;m trying to insert `CLOB`s into a database (see [related question][1]). I can&#39;t quite figure out what&#39;s wrong. I have a list of about 85 clobs I want to insert into a table. Even when inserting only the first clob I get `ORA-00911: invalid character`. I can&#39;t figure out how to get the statement out of the `PreparedStatement` before it executes, so I can&#39;t be 100% certain that it&#39;s right, but if I got it right, then it should look exactly like this:

    insert all
      into domo_queries values (&#39;select 
    substr(to_char(max_data),1,4) as year,
    substr(to_char(max_data),5,6) as month,
    max_data
    from dss_fin_user.acq_dashboard_src_load_success
    where source = &#39;&#39;CHQ PeopleSoft FS&#39;&#39;&#39;)
    select * from dual;

Ultimately, this [`insert all`][2] statement would have a lot of `into`&#39;s, which is why I just don&#39;t do a regular `insert` statement. I don&#39;t see an invalid character in there, do you? (Oh, and that code above **runs fine when I run it in my sql developer tool**.) And I if I remove the semi-colon in the `PreparedStatement`, it throws an `ORA-00933: SQL command not properly ended` error.

In any case, here&#39;s my code for executing the query (and the values of the variables for the example above).

    public ResultSet executeQuery(String connection, String query, QueryParameter... params) throws DataException, SQLException {
      // query at this point = &quot;insert all
                              //into domo_queries values (?)
                              //select * from dual;&quot;
      Connection conn = ConnectionPool.getInstance().get(connection);
      PreparedStatement pstmt = conn.prepareStatement(query);
      for (int i = 1; i &lt;= params.length; i++) {
        QueryParameter param = params[i - 1];
        switch (param.getType()) { //The type in the example is QueryParameter.CLOB
          case QueryParameter.CLOB:
            Clob clob = CLOB.createTemporary(conn, false, oracle.sql.CLOB.DURATION_SESSION);
            clob.setString(i, &quot;&#39;&quot; + param.getValue() + &quot;&#39;&quot;);
            //the value of param.getValue() at this point is:
            /*
             * select 
             * substr(to_char(max_data),1,4) as year,
             * substr(to_char(max_data),5,6) as month,
             * max_data
             * from dss_fin_user.acq_dashboard_src_load_success
             * where source = &#39;&#39;CHQ PeopleSoft FS&#39;&#39;
             */
            pstmt.setClob(i, clob);
            break;
          case QueryParameter.STRING:
            pstmt.setString(i, &quot;&#39;&quot; + param.getValue() + &quot;&#39;&quot;);
            break;
        }
      }
      ResultSet rs = pstmt.executeQuery(); //Obviously, this is where the error is thrown
      conn.commit();
      ConnectionPool.getInstance().release(conn);
      return rs;
    }

Is there anything I&#39;m just missing big time?


  [1]: https://stackoverflow.com/questions/10727521/
  [2]: http://www.techonthenet.com/oracle/questions/insert_rows.php

Where&#39;s my invalid character (ORA-00911)

I&#39;m looking for a way to rename a Hashmap key, but i don&#39;t know if it&#39;s possible in Java.

Is it possible to rename a Hashmap key?

I am looking at the implementation of `HashMap` in Java and am stuck at one point.&lt;BR&gt;
How is the `indexFor` function calculated?

    static int indexFor(int h, int length) {
       return h &amp; (length-1);
    }

Thanks


HashMap implementation in Java. How does the bucket index calculation work?

`HashMap` has two important properties: `size` and `load factor`. I went through the Java documentation and it says `0.75f` is the initial load factor. But I can&#39;t find the actual use of it. 

Can someone describe what are the different scenarios where we need to set load factor and what are some sample ideal values for different cases?

What is the significance of load factor in HashMap?

How do I swap keys and values in a Hash?

I have the following Hash:

    {:a=&gt;:one, :b=&gt;:two, :c=&gt;:three}

that I want to transform into:

    {:one=&gt;:a, :two=&gt;:b, :three=&gt;:c}

Using `map` seems rather tedious. Is there a shorter solution?

How to swap keys and values in a hash

I am using a Runnable to automatically subtract 20 from a players cooldown every second, but I have no idea how to replace the value of a value as I iterate through it. How can I have it update the value of each key?

	public class CoolDownTimer implements Runnable {
		@Override
		public void run() {
			for (Long l : playerCooldowns.values()) {
				l = l - 20;
				playerCooldowns.put(Key???, l);
			}
		}
		
	}

Content Type	Original Author	Original Content on Stackoverflow
Question	realtebo	View Question on Stackoverflow
Solution 1 - Java	NPE	View Answer on Stackoverflow
Solution 2 - Java	nicholas.hauschild	View Answer on Stackoverflow

How to preserve insertion order in HashMap?

Java Problem Overview

Java Solutions

Solution 1 - Java

Solution 2 - Java

The Use of Multiple JFrames: Good or Bad Practice?

Why is whitespace sometimes needed around metacharacters?

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