package electric.electricUtils;import java.sql.*;import java.util.*;public class DbSequenceManager {  private static final String LOAD_ID =      "SELECT SEQUENCEID FROM SEQUENCETABLE WHERE TABLENAME=?";  private static final String UPDATE_ID =      "UPDATE SEQUENCETABLE SET SEQUENCEID=? WHERE TABLENAME=? AND SEQUENCEID=?";  private static final String INSERT_ID =      "INSERT INTO SEQUENCETABLE (SEQUENCEID,TABLENAME) VALUES(?,?)";  private static final int INCREMENT = 1;  private static DbSequenceManager[] managers;  static {    managers = new DbSequenceManager[FinalConstants.TABLENUM];    for (int i = 0; i < managers.length; i++) {      managers[i] = new DbSequenceManager(i);    }  }  public static int nextID(int type) {    return managers[type].nextUniqueID();  }  private int type;  private int currentID;  public DbSequenceManager(int type) {    this.type = type;    currentID = 0;  }  public synchronized int nextUniqueID() {    getNextBlock();    int id=currentID+INCREMENT;    return id;  } private void getNextBlock() {    boolean success = false;    Connection con = null;    PreparedStatement pstmt = null;    try {      con = DbConnectionManager.getConnection();      pstmt = con.prepareStatement(LOAD_ID);      pstmt.setInt(1, type);      ResultSet rs = pstmt.executeQuery();      if (!rs.next()) {        pstmt = con.prepareStatement(INSERT_ID);        pstmt.setInt(1, currentID);        pstmt.setInt(2, type);        pstmt.executeUpdate();      }      else {        currentID = rs.getInt(1);      }      pstmt.close();      int newID = currentID + INCREMENT;      pstmt = con.prepareStatement(UPDATE_ID);      pstmt.setInt(1, newID);      pstmt.setInt(2, type);      pstmt.setInt(3, currentID);      success = pstmt.executeUpdate() == 1;      if (success) {        this.currentID = currentID;      }    }    catch (Exception sqle) {      sqle.printStackTrace();    }    finally {      try {        pstmt.close();      }      catch (Exception e) {        e.printStackTrace();      }      try {        con.close();      }      catch (Exception e) {        e.printStackTrace();      }    }    if (!success) {      System.err.println("WARNING: failed to obtain next ID block due to " +                         "thread contention. Trying again...");       getNextBlock();    }  }}