Help: OutOfMemoryError

When I use export a lager table, the java application throws exception 'OutOfMemoryError',
How can I do ? this is the source:

/*
export table
*/

import java.io.*;
import java.sql.*;
import java.util.*;

public class ExpTbl_MS {

private static String db_res[][] = {
{ "com.ashna.jturbo.driver.Driver", "jdbc:JTurbo://egcs:1433/egcs/charset=GBK" },
{ "net.avenir.jdbc2.Driver", "jdbc:AvenirDriver://172.16.1.156:1433/fpb" },
{ "org.gjt.mm.mysql.Driver", "jdbc:mysql://egcs:3306/fpb?useUnicode=true&characterEncoding=gb2312&autoReconnect=true" },
{ "org.postgresql.Driver", "jdbc:postgresql://orchis:5432/fpb" },
{ "oracle.jdbc.driver.OracleDriver", "jdbc:oracle:thin:@202.100.100.201:1521:ORA" },
{ "COM.ibm.db2.jdbc.net.DB2Driver", "jdbc:db2://egcs:6789/fpb" },
{ "sun.jdbc.odbc.JdbcOdbcDriver", "jdbc:odbc:sql" },
{ "com.ms.jdbc.odbc.JdbcOdbcDriver", "jdbc:odbc:sql" },
};

public static void main(String[] args) throws Exception {

int i = 0, j;
String db_drv = "com.ashna.jturbo.driver.Driver";
String db_url = "jdbc:JTurbo://172.16.19.2:1433/agriec/charset=GBK";
String db_usr = "sa";
String db_pwd = "zm";
String db_exp = "ExpTbl_MS.dmp";

while(i < args.length) {
if(args[i].startsWith("db_drv=")) {
db_drv = args[i].substring(7);
} else if(args[i].startsWith("db_url=")) {
db_url = args[i].substring(7);
} else if(args[i].startsWith("db_usr=")) {
db_usr = args[i].substring(7);
} else if(args[i].startsWith("db_pwd=")) {
db_pwd = args[i].substring(7);
} else if(args[i].startsWith("db_exp=")) {
db_exp = args[i].substring(7);
} else {
break;
}
i++;
}

Class.forName(db_drv);

Connection db_cn = DriverManager.getConnection(db_url, db_usr, db_pwd);

//Statement db_st = db_cn.createStatement();
Statement db_st = db_cn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_READ_ONLY);
for(j = 0; i < args.length; i++) {
try {
System.out.print("starting export table '" + args[i] + "' ");
export(db_st, args[i], (db_exp + "." + j));
System.out.println(" OK");
} catch(Exception se) {
System.out.println(" Fail(" + se.getMessage() + ")");
}
System.out.println("\n");
}

db_st.close();
db_cn.close();
}

public static void export(Statement db_st, String tableName, String of)
throws SQLException, IOException {

ObjectOutputStream os = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(of), 512 * 1024));
ResultSet db_rs = db_st.executeQuery("select * from " + tableName);
ResultSetMetaData db_rsmd = db_rs.getMetaData();
int i, j, n = db_rsmd.getColumnCount();
Object obj;

os.writeInt(0);
os.writeObject(tableName);
os.writeInt(n);
for(i = 1; i <= n; i++) {
os.writeObject(db_rsmd.getColumnName(i));
os.writeObject(db_rsmd.getColumnTypeName(i));
os.writeInt(db_rsmd.getColumnDisplaySize(i));
os.writeInt(db_rsmd.getPrecision(i));
os.writeInt(db_rsmd.getScale(i));
os.writeInt(db_rsmd.isNullable(i));
}

for(j = 0; db_rs.next(); j++) {
for(i = 1; i <= n; i++) {
obj = db_rs.getObject(i);
if(obj == null || db_rs.wasNull()) {
os.writeObject(null);
} else if(obj instanceof byte[]) {
os.writeObject(obj);
} else if(obj instanceof java.sql.Timestamp ||
obj instanceof java.sql.Date ||
obj instanceof java.sql.Time
) {
os.writeObject(new java.lang.Long(((java.util.Date)obj).getTime()));
} else if(obj instanceof java.sql.Blob) {
Blob blob = (Blob)obj;
os.writeObject(blob.getBytes(1L, (int)blob.length()));
blob = null;
} else if(obj instanceof java.sql.Clob) {
Clob clob = (Clob)obj;
os.writeObject(clob.getSubString(1L, (int)clob.length()));
clob = null;
} else if(obj instanceof java.io.InputStream) {
System.err.print("Unknown, ");
} else {
os.writeObject(obj.toString());
}
obj = null;
}
if(j % 1000 == 0) {
System.out.print('.');
System.gc();
System.runFinalization();
System.gc();
os.flush();
}
}
}
}