java mysql java.lang.OutOfMemoryError: Java heap space

java mysql java.lang.OutOfMemoryError: Java heap space

I developed a web scraper. The Web scraper uses 6 threads, each thread
opens a web page, gets the text of an article, than writes (using a
driver) each single word of the text in a mysql database.
During the execution of the program i get a java mysql
java.lang.OutOfMemoryError: Java heap space. I installed Memory Analyzer
on Eclipse and i found that the problem is caused by the mysql driver
connection: i start a program and after 5 minutes the ram occupied by the
driver is 6 MB, after another 5 minutes 200MB, after other 5 minutes 500Mb
and then i get the java error heap space.
I don't understand why this happens.
Here is the code i use for the model (to access mysql DB)
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
public class model {
private Connection connect = null;
public model(){
try {
Class.forName("com.mysql.jdbc.Driver");
connect =
DriverManager.getConnection("jdbc:mysql://localhost/system?user=keyword_tool&password=l0gripp0");
} catch (Exception e) {
System.out.println(e);
}
}
public synchronized void insertCat(String parola, String categoria){
try{
PreparedStatement statement = connect.prepareStatement("insert
into sostantivi (nome, categoria) values (?, ?)");
statement.setString(1, parola);
statement.setString(2, categoria);
statement.executeUpdate();
statement.close();
} catch (Exception e){
//System.out.println(e);
}
}
public void closeDBConnection() {
try {
connect.close();
} catch (Exception e) {
System.out.println(e);
}
}
}
Each thread simply call the method insertCat and insert a word with a
category in the database.
The Memory Analyzer plugin of Eclipse says: