but watch out for this....

    Long nullLong = null;

    preparedStatement.setLong( nullLong );

-thows null pointer exception-



because the protype is

    setLong( long )   
NOT

    setLong( Long )

nice one to catch you out eh.

This [guide](https://docs.oracle.com/javase/1.5.0/docs/guide/jdbc/getstart/preparedstatement.html) says:

&gt; #### 6.1.5 Sending JDBC NULL as an IN parameter
&gt;
&gt; The `setNull` method allows a programmer to send a JDBC `NULL` (a generic SQL `NULL`) value to the database as an IN parameter. Note, however, that one must still specify the JDBC type of the parameter.
&gt;
&gt; A JDBC `NULL` will also be sent to the database when a Java `null` value is passed to a `setXXX` method (if it takes Java objects as arguments). The method `setObject`, however, can take a `null` value only if the JDBC type is specified.

So yes they&#39;re equivalent.

Finally I did a small test and while I was programming it it came to my mind, that without the setNull(..) method there would be no way to set null values for the Java primitives. For Objects both ways 

    setNull(..)

and 

    set&lt;ClassName&gt;(.., null)) 

behave the same way.

You could also consider using `preparedStatement.setObject(index,value,type);`

    preparedStatement.setNull(index, java.sql.Types.NULL);

that should work for any type.
Though in some cases failure happens on the server-side, like:
for SQL:

    COALESCE(?, CURRENT_TIMESTAMP)

`Oracle 18XE` fails with the wrong type: expected `DATE`, got `STRING` -- that is a perfectly valid failure; 

Bottom line: it is good to know the type if you call `.setNull()` 

UPDATE: stackoverflow need to hire more editors to add\remove punctuation to my posts here

I want to programmatically [in C] calculate CPU usage % for a given process ID in Linux.

How can we get the realtime CPU usage % for a given process?

To make it further clear:

 - I should be able to determine the CPU usage for the provided processid or process.  
 - The process need not be the child process.  
 - I want the solution in &#39;C&#39; language.

How to calculate the CPU usage of a process by PID in Linux from C?

In my Rails template, I&#39;d like to accomplish final HTML to this effect using HAML:

    I will first &lt;a href=&quot;http://example.com&quot;&gt;link somewhere&lt;/a&gt;, then render this half of the sentence if a condition is met

The template that comes close:

    I will first
    = link_to &#39;link somewhere&#39;, &#39;http://example.com&#39;
    - if @condition
      , then render this half of the sentence if a condition is met

You may, however, note that this produces a space between the link and the comma. Is there any practical way to avoid this whitespace? I know there&#39;s syntax to remove whitespace around tags, but can this same syntax be applied to just text? I really don&#39;t like the solution of extra markup to accomplish this.

Haml: Control whitespace around text

Java PreparedStatement provides a possibility to explicitely set a Null value. This possibility is:

    prepStmt.setNull(parameterIndex, Types.VARCHAR);

Are the semantics of this call the same as when using a specific setType with a null parameter?

    prepStmt.setString(null);

?

PreparedStatement setNull(..)

Java PreparedStatement provides a possibility to explicitely set a Null value. This possibility is:
<pre><code class="hljs language-ini">prepStmt.setNull(parameterIndex, Types.VARCHAR);
</code></pre>
Are the semantics of this call the same as when using a specific setType with a null parameter?
<pre><code class="hljs language-csharp">prepStmt.setString(null);
</code></pre>
?

I defined my own custom annotation

    @Target(value={ElementType.METHOD, ElementType.FIELD})
    @Retention(RetentionPolicy.RUNTIME)
    public @interface MyCustomAnnotation  {
	    Class&lt;?&gt; myType();
    }

how, if at all, can I make the attribute optional


java custom annotation: make an attribute optional

In Java, How to compose a HTTP request message and send it to a HTTP WebServer?


How to send HTTP request in java?

I was trying to make my own class for currencies using longs, but apparently I should use `BigDecimal` instead. Could someone help me get started? What would be the best way to use `BigDecimal`s for dollar currencies, like making it at least but no more than 2 decimal places for the cents, etc. The API for `BigDecimal` is huge, and I don&#39;t know which methods to use. Also, `BigDecimal` has better precision, but isn&#39;t that all lost if it passes through a `double`? if I do new `BigDecimal(24.99)`, how will it be different than using a `double`? Or should I use the constructor that uses a `String` instead?

Using BigDecimal to work with currencies

I have a function that uses `Pattern#compile` and a `Matcher` to search a list of strings for a pattern.  

This function is used in multiple threads. Each thread will have a unique pattern passed to the `Pattern#compile` when the thread is created.  The number of threads and patterns are dynamic, meaning that I can add more `Pattern`s and threads during configuration.

Do I need to put a `synchronize` on this function if it uses regex?  Is regex in java thread safe?


Is Java Regex Thread Safe?

In an annotation-based Spring MVC controller, what is the preferred way to set cache headers for a specific path?

How do you set cache headers in Spring MVC?

I am new to JDBC and I am trying to make a connection to a MySQL database.
I am using Connector/J driver, but I cant find the JDBC connection string for my `Class.forName()` method.



What is the MySQL JDBC driver connection string?

&gt; **Possible Duplicate:**  
&gt; [Running a .sql script using MySQL with JDBC](https://stackoverflow.com/questions/1044194/running-a-sql-script-using-mysql-with-jdbc)  

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

I have an SQL script file which contains 40-50 SQL statements. Is it possible to run this script file using JDBC?


How to execute .sql script file using JDBC

I am using one simple code to access the SQLite database from Java application .
My code is

     import java.sql.Connection;  
     import java.sql.DriverManager;  
     import java.sql.ResultSet;  
     import java.sql.Statement;  
     public class ConnectSQLite 
     {  
      public static void main(String[] args) 
      {  
         Connection connection = null;  
         ResultSet resultSet = null;  
         Statement statement = null;  
   
         try 
         {  
             Class.forName(&quot;org.sqlite.JDBC&quot;);  
             connection = DriverManager.getConnection(&quot;jdbc:sqlite:D:\\testdb.db&quot;);  
             statement = connection.createStatement();  
             resultSet = statement  
                     .executeQuery(&quot;SELECT EMPNAME FROM EMPLOYEEDETAILS&quot;);  
             while (resultSet.next()) 
             {  
                 System.out.println(&quot;EMPLOYEE NAME:&quot;  
                         + resultSet.getString(&quot;EMPNAME&quot;));  
             }  
         } 
         catch (Exception e) 
         {  
             e.printStackTrace();  
         }
         finally 
         {  
             try 
             {  
                 resultSet.close();  
                 statement.close();  
                 connection.close();  
             } 
             catch (Exception e) 
             {  
                 e.printStackTrace();  
             }  
         }  
     }  
    }  

But this code gives one exception like

    java.lang.ClassNotFoundException: org.sqlite.JDBC

How can I slove this,please help me.

How to connect SQLite with Java?

To rephrase the question: should I avoid sharing instances of classes which implement `java.sql.Connection` between different threads?

Is java.sql.Connection thread safe?

I know that PreparedStatements avoid/prevent SQL Injection. How does it do that? Will the final form query that is constructed using PreparedStatements be a string or otherwise?

How does a PreparedStatement avoid or prevent SQL injection?

Is there a way to retrieve the auto generated key from a DB query when using a java query with prepared statements. 

For example, I know AutoGeneratedKeys can work as follows. 

    stmt = conn.createStatement();

    stmt.executeUpdate(sql, Statement.RETURN_GENERATED_KEYS);
    if(returnLastInsertId) {
        ResultSet rs = stmt.getGeneratedKeys();
        rs.next();
        auto_id = rs.getInt(1);
    } 

However. What if I want to do an insert with a prepared Statement. 

    String sql = &quot;INSERT INTO table (column1, column2) values(?, ?)&quot;;
    stmt = conn.prepareStatement(sql);
            
    //this is an error
    stmt.executeUpdate(Statement.RETURN_GENERATED_KEYS);
    if(returnLastInsertId) {
        //this is an error since the above is an error
        ResultSet rs = stmt.getGeneratedKeys();
        rs.next();
        auto_id = rs.getInt(1);
    } 

Is there a way to do this that I don&#39;t know about. It seems from the javadoc that PreparedStatements can&#39;t return the Auto Generated ID.

Is there a way to retrieve the autoincrement ID from a prepared statement

I worked on a PHP project earlier where prepared statements made the SELECT queries 20% faster.

I&#39;m wondering if it works on Python? I can&#39;t seem to find anything that specifically says it does or does NOT.



Does Python support MySQL prepared statements?

I have a general Java method with the following method signature:

    private static ResultSet runSQLResultSet(String sql, Object... queryParams)

It opens a connection, builds a `PreparedStatement` using the sql statement and the parameters in the `queryParams` variable length array, runs it, caches the `ResultSet` (in a `CachedRowSetImpl`), closes the connection, and returns the cached result set.

I have exception handling in the method that logs errors. I log the sql statement as part of the log since it&#39;s very helpful for debugging. My problem is that logging the String variable `sql` logs the template statement with ?&#39;s instead of actual values. I want to log the *actual* statement that was executed (or tried to execute).

So... Is there any way to get the actual SQL statement that will be run by a `PreparedStatement`? (*Without* building it myself. If I can&#39;t find a way to access the `PreparedStatement&#39;s` SQL, I&#39;ll probably end up building it myself in my `catch`es.)



How can I get the SQL of a PreparedStatement?

in the case of using PreparedStatement with a single common connection without any pool, can I recreate an instance for every dml/sql operation mantaining the power of prepared statements? 

I mean:

    for (int i=0; i&lt;1000; i++) {
        PreparedStatement preparedStatement = connection.prepareStatement(sql);
        preparedStatement.setObject(1, someValue);
        preparedStatement.executeQuery();
        preparedStatement.close();
    }

instead of:

    PreparedStatement preparedStatement = connection.prepareStatement(sql);
    for (int i=0; i&lt;1000; i++) {
        preparedStatement.clearParameters();
        preparedStatement.setObject(1, someValue);
        preparedStatement.executeQuery();
    }
    preparedStatement.close();

my question arises by the fact that I want to put this code into a multithreaded environment, can you give me some advice? thanks

Content Type	Original Author	Original Content on Stackoverflow
Question	paweloque	View Question on Stackoverflow
Solution 1 - Java	Owen	View Answer on Stackoverflow
Solution 2 - Java	djna	View Answer on Stackoverflow
Solution 3 - Java	paweloque	View Answer on Stackoverflow
Solution 4 - Java	bithom	View Answer on Stackoverflow
Solution 5 - Java	Dmitriy Pichugin	View Answer on Stackoverflow

PreparedStatement setNull(..)

Java Problem Overview

Java Solutions

Solution 1 - Java

Solution 2 - Java

Solution 3 - Java

Solution 4 - Java

Solution 5 - Java

Haml: Control whitespace around text

How to calculate the CPU usage of a process by PID in Linux from C?

Attributions