给领导送礼怎么送:帮忙看下这个JAVA BEANS文件，有些地方我不懂

import java.sql.*;
public class dbconn
{
Connection con;
ResultSet rs;
public dbconn()
{ try{Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
}
catch(ClassNotFoundException e){
System.err.println(e.getMessage());
}
}
public ResultSet executeQuery(String sql)
{ try{con=DriverManager.getConnection("jdbc:odbc:research","","");
Statement stm=con.createStatement();
rs=stm.executeQuery(sql);
}
catch(SQLException ex){
System.err.println(ex.getMessage());
}
return rs;
}
<h2>public int executeUpdate(String sql)</h2>
{ int result=0;
try{con=DriverManager.getConnection("jdbc:odbc:research","","");
Statement stmt=con.createStatement();
result=stmt.executeUpdate(sql);
}
catch(SQLException ex){
System.err.println(ex.getMessage());
}
return result;
}
}
import java.sql.*;
public class dbconn
{
Connection con;
ResultSet rs;
public dbconn()
{ try{Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
}
catch(ClassNotFoundException e){
System.err.println(e.getMessage());
}
}
public ResultSet executeQuery(String sql)
{ try{con=DriverManager.getConnection("jdbc:odbc:research","","");
Statement stm=con.createStatement();
rs=stm.executeQuery(sql);
}
catch(SQLException ex){
System.err.println(ex.getMessage());
}
return rs;
}
public int executeUpdate(String sql)//为什么这用的是INT？
{ int result=0;//这也不懂
try{con=DriverManager.getConnection("jdbc:odbc:research","","");
Statement stmt=con.createStatement();
result=stmt.executeUpdate(sql);
}
catch(SQLException ex){
System.err.println(ex.getMessage());
}
return result;
}
}