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The method list() in the File class can help you to achieve this purpose.

A meta-character is a characater that has special meaning to a computer program.

for example , in the regular expression engine:

A sequential file contains records organized by the order where they are entered , 

the length of records and the order of records are fixed.

We need to use URLConnection class or HttpURLConnection class to set cookie.

The example is as below:

When we crawl the content from the URL , sometimes the process will become zombie and the task will

be stoped by some internet connection reason.

In File class , there is a method , mkdir() , which can be used to create directory.

The example is as below:

boolean success = (new File("directoryName")).mkdir();

if (!success) 

{

 System.out.println("Directory create failed!!");

}

In File class , it also has another method , mkdirs() , we can use this method if we want to create hierarchical directory .

for example:

This example will create two directory , one is datasets directory , and the other is class_2 directory.

String classNum = "datasets\\class_"+2;

How to retrun a two dimensional array , 

It is very simple in Java , we just need to set the return type as the same as the array tyep.

有時候 , 我們可能不只有一組data , 而昰有很多組data , 

但是對每組data我們可能會想使用不同的Hashtable , 

The range of ascii is from 0 to 255 , 

so a character is out of this range , we can say that this character is not a ascii.

javadoc is a tool in the jdk folder , it can help us transform the comment which was in program

to a documentation which was html style .

When we write many program , we also need to manage these program in order to avoid confuse.

Java has provide two method for us to manage these program , Package and Jar.

We can use the method , charAt() , to extract the word in the string.

for example:

There are three ways to set Classpath.

1. Using command

The method , delete() , of File class can be used to delete the file.

The method , length() , of File class can be used to get the file size.

File f = new File(fileName);

The System.out will be changed to test file after the instruction , System.setOut(new PrintStream("test")) ,

is executed.

We can use File class to open a folder and read the file name of this folder.

and the method , list() , will return an array of strings naming the files in the directory.

Sometimes , we may want to sent parameter by POST method , 

the following example can help us achieve this purpose.

String str = "String that you want to transmit";

// Create a socket to the host

public class QueueTest