Scott: /* Database */

2011-01-31T21:45:32Z

Database

New page

==Streams==
Reading a text file (Core Java, p645):
<source lang="java">
BufferedReader in = new BufferedReader(new FileReader("employee.txt"));
...
String s;
while ((s = in.readLine()) != null){
..do stuff with s...
}
</source>

Reading Unicode characters from a text file:
<source lang="java">
BufferedReader in = new BufferedReader(new FileReader("employee.txt"));
...
char c;
while ((c = (char)in.read()) >= 0){
..do stuff with c...
}
</source>

Reading bytes from a generic data file:
<source lang="java">
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(fileName);
int n;
while ((n = bis.read()) > -1){
..do stuff with n..
}
</source>

Reading from the command line (p66)
<source lang="java">
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
...
String s = in.readLine();
..do stuff with s...
</source>

Writing to a text file:
<source lang="java">
PrintWriter out = new PrintWriter(new FileWriter("employee.txt"));
println("some text");
println("some more text");
out.flush(); // won't write until you call this
</source>

PrintWriter and Autoflush: If this is on, the file is written to whenever you call <code>println()</code>.
There are two constructors:
<source lang="java">
PrintWriter(String filename)
</source>
has autoflush off by default. In this case, you must call
<source lang="java">
out.flush();
</source>
to get the output written!

Use
<source lang="java">
PrintWriter(String filename, boolean autoflush)
</source>
to turn autoflush on.

The PrintWriter is buffered, so you don't need to throw in a buffered writer.

FileWriter and Appending: use
<source lang="java">
new FileWriter("employee.txt", true)
</source>
to append.

==Database==
(need driver file on your classpath)

Example:
<source lang="java">
import java.sql.*;
...
public static void testConnection(){
// String url = "jdbc:odbc:tk1dev" ;
// String url = "jdbc:oracle:thin:@es01:1521:tk1DEV";
String url = "jdbc:mysql://localhost/test";
Connection con = null;
try {
// Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
// Class.forName("oracle.jdbc.driver.OracleDriver");
Class.forName("com.mysql.jdbc.Driver");
} catch(java.lang.ClassNotFoundException e) {
e.printStackTrace();
return;
}
try {
con = DriverManager.getConnection(url, "tk", "xxxxxxxx");
Statement statement = con.createStatement();
//String queryString = "select sysdate from dual";
String queryString = "select now()";
ResultSet rs = statement.executeQuery(queryString);
while (rs.next()){
System.out.println("result is "+rs.getTimestamp(1));
}
} catch(SQLException e) {
e.printStackTrace();
} finally {
try{
con.close();
} catch(SQLException e) {
e.printStackTrace();
}
}
}
</source>

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Scott: /* Database */