Order of Tags in Java comments

Order of Tags
Include tags in the following order:

• @author (classes and interfaces only, required)
• @version (classes and interfaces only, required.)
• @param (methods and constructors only)
• @return (methods only)
• @exception (@throws is a synonym added in Javadoc 1.2)
• @see
• @since
• @serial (or @serialField or @serialData)
• @deprecated 

GIT: showing only list of modified files in a commit

git show --pretty="format:" --name-only  6773e94744fd6885f0737655e491f075afb8c80a

Output:

trunk/guieditor/src/com/pat/tool/keditor/editors/SAPServerDetailsDialog.java
trunk/guieditor/src/com/pat/tool/service/model/SAPServer.java
trunk/guieditor/src/com/pat/tool/service/model/SAPServerUtil.java

The protocol of IProgressMonitor

Very nice write-up on this:
http://www.eclipse.org/articles/Article-Progress-Monitors/article.html
http://www.eclipse.org/articles/Article-Progress-Monitors/article.html#Ensure_to_always_complete_your_monitor


One contract pattern described above is that if beginTask() is ever called, done() MUST be called. This is achieved by always following this code pattern (all code is simplified):

monitor = … // somehow get a new progress monitor which is in a pristine state
// figure some things out such as number of items to process etc…
try
 {
 monitor.beginTask(…)
 // do stuff and call worked() for each item worked on, and check for cancellation
 }
finally
 {
 monitor.done()
 }

Javascript functions and difference

The two ways to declare a java script function:

var functionOne = function() {
    // Some code
};

function functionTwo() {
    // Some code
}

The difference is that functionTwo is defined at parse-time for a script block, whereas functionOneis defined at run-time. For example:

<script>
  // Error
  functionOne();

  var functionOne = function() {
  }
</script>

<script>
  // No error
  functionTwo();

  function functionTwo() {
  }
</script>

StringBuilder with modern compilers

Modern Java compiler convert your + operations by StrinBuilder's append. I mean to say if you do str = str1+sr2+str3 then compiler will generate following code

StringBuilder sb = new StringBuilder();
str = sb.append(str1).append(str2).append(str3).toString();

So now its more of matter of choice than performance benefit to use + or StringBuilder :)

JVM: Finding the process id

package com.kk.memory.tool;

import sun.management.VMManagement;
import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;
import java.lang.reflect.Field;
import java.lang.reflect.Method;

public class FindJavaProcessId {

public static void main(String[] args) {

try {
RuntimeMXBean runtimeMXBean = ManagementFactory.getRuntimeMXBean();
Field jvmField = runtimeMXBean.getClass().getDeclaredField("jvm");
jvmField.setAccessible(true);
VMManagement vmManagement = (VMManagement) jvmField.get(runtimeMXBean);
Method getProcessIdMethod = vmManagement.getClass().getDeclaredMethod("getProcessId");
getProcessIdMethod.setAccessible(true);
Integer processId = (Integer) getProcessIdMethod.invoke(vmManagement);
System.out.println("################    ProcessId = " + processId);
} catch (Exception e) {
e.printStackTrace();
}
}

}

String vs StringBuilder performance trade-offs

public class StringTest {

public static void main(String[] args) {

int[] runfor = { 10, 100, 1000, 10000 };

for (int i = 0; i < runfor.length; i++) {
long start = System.currentTimeMillis();
String s = "";
for (int j = 0; j < runfor[i]; j++) {
s += "Hello" + "--" + "World!!!";
}
long end = System.currentTimeMillis();
System.out.println("String concatenation x " + runfor[i] + " times: " + (end - start) + " miliseconds");

start = System.currentTimeMillis();
StringBuilder sb = new StringBuilder();
for (int j = 0; j < runfor[i]; j++) {
sb.append("Hello");
sb.append("--");
sb.append("World!!!");
}
end = System.currentTimeMillis();
System.out.println("StringBuilder concatenation x " + runfor[i] + " times: " + (end - start) + " miliseconds");
}
}
}

Results:

String concatenation x 10 times: 0 miliseconds

StringBuilder concatenation x 10 times: 0 miliseconds

String concatenation x 100 times: 1 miliseconds

StringBuilder concatenation x 100 times: 0 miliseconds

String concatenation x 1000 times: 15 miliseconds

StringBuilder concatenation x 1000 times: 1 miliseconds

String concatenation x 10000 times: 1143 miliseconds

StringBuilder concatenation x 10000 times: 3 miliseconds