Why transfer content from one file to another? When we do analysis on content in files, we may need to read content from one file and do various kinds of processing (e.g. exclude/add/modify some parts), and then output results to another file. This process occurs very often if you do simple program analysis or file … Read more
Replace vs Append/Add If you want your code to create a new file and erase previous existing file, FileWriter can simply take it place. To replace all content in an existing file, use this: FileWriter fstream = new FileWriter(loc);FileWriter fstream = new FileWriter(loc); The code above will delete the existing file if it’s name is … Read more
This post summarizes the classes that can be used to write a file. 1. FileOutputStream public static void writeFile1() throws IOException { File fout = new File("out.txt"); FileOutputStream fos = new FileOutputStream(fout); BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(fos)); for (int i = 0; i < 10; i++) { bw.write("something"); bw.newLine(); } bw.close(); … Read more
Processing a text file line by line is a common thing programmers do. There are many related classes in the Java I/O package and this may get confusing. This post shows 4 different ways of reading a file line by line in Java. 1. FileInputStream and BufferedReader private static void readFile1(File fin) throws IOException { … Read more
This is a method that accepts a range (max) and a number (n), returns an array of n random numbers. n: size of random number array max: largest available number (exclusive) For example: Input: n=5, max=100 Output: an array containing 5 random numbers whose range is from 0 to 99. public static HashSet<Integer> getNRandom(int n, … Read more
To keep the unique value of a large data set, Set would be a good option. Every element in a set is unique, when a duplicate element is added, it is ignored. Here is a sample code from oracle. public class FindDups2 { public static void main(String[] args) { Set<String> uniques = new HashSet<String>(); Set<String> … Read more
If you have a file with come words or terms on each line, you may want to sort it. Java Arrays.sort is common nice function to do this. Collections.sort() is another nice say. Here is an example and code.
E.G. in a file, you have the following txt.
dog cat --windows --kankan pps game --annot be guaranteed as it is, generally speaking, --impossible to make any hard gu arantees in the p --resence of unsynchr |
While programming for a small project under Eclipse IDE, I got the following error message: java.lang.UnsupportedClassVersionError: Bad version number in .class file The problem is the compilation JRE and running JRE are not the same. So we need to make them the same version, e.g. 1.6. There also might be the JRE library in your … Read more
First of all, You will need to add a jar file to your project library as SQL Server 2000 Driver for JDBC Service. My target is SQL Server 2000, it will require the jar file called “sqljdbc4.jar”. This is not supported on Microsoft website now, you can download it here. For other versions of SQL Server, here is the link of SQL Server 2000 Driver for JDBC Service.
The following is the code for connection MS SQL Server and select some records from a testing table.
To connect MS SQL Server using windows authentication, the first step is to setup ODBC. You can go to Control panel -> Administrative tools -> ODBC. Add a new DSN to connect MS SQL Server using windows authentication account following wizard setup. The second step is the similar with using SQL Server authentication. The only … Read more
Can we make a database connection class which allows us just change the configuration file, and then use the database? I did the prototype of this class which is very simple. But the idea is good, always use a very simple jar file to get setup database which can then do SQL query operations. package … Read more
For configuration purposes, using properties file is a good way of reusing. In this way, when the code is packaged to a jar file, other users can just put the different configurations in the config.properties file. The following is a simple example of using properties file. 1. create the file hierarchy like the following. Mainly … Read more
By using eclipse export wizard, you can get executable jar files. But the jar file can be only launched by using command lines. Apparently, this is not a good option for most regular not-java-programmer users, especially if the program requires user’s input to proceed. We need a program which can be started by double clicking. … Read more
I want to refresh my blog on Sohu to increase the visitor count. The following is the code for open IE browser and then close it. This will be done every 5 seconds, and in one day the count should be able to increase 3600*24/5 = 17280. So if you open your computer 10 days, the count will become 172800. That will be a nice number.
The following is the code for reading html content of a web page. Using java to read web page is different from using Java to call IE to open web pages. The visitor count for a general blog can not increase in this way. To increase visitors count, you need a program that can call … Read more