Solved

NullPointerException ???

Posted on 2004-04-18
4
270 Views
Last Modified: 2010-03-31
Hi.. I keep getting NullPointerException and can't seem to figure out what is wrong with my code? Anybody have any ideas? Thanks in advance

=-=-= stdout -=-=-=-
Exception in thread "main" java.lang.NullPointerException
        at accountServicesInterface.getAllEntries(accountServicesInterface.java:24)
        at accountServicesInterface.main(accountServicesInterface.java:79)

=-=-= java code -=-=-
package com.bedlam.accountServices.common;

import com.bedlam.accountServices.database.*;
import com.bedlam.accountServices.common.LogWriter;

import java.sql.*;

public class accountServicesInterface {
  private Database db;
  private Table table;
  private String tableName;

  public accountServicesInterface(String tableName) {
    db = new Database();
    Table table = db.getTable(tableName);
    this.tableName = tableName;
  }

  public Row getEntry(String crit) throws SQLException {
    return table.getRow(crit);
  }

  public RowSet getAllEntries(String crit) throws SQLException {
    return table.getRows(crit);
  }

  public int generateRandomID() {
    if (tableName.equals("UserClient"))
      return (int)(Math.random()*15000);
    else
      return (int)(Math.random()*30000+15000);
  }

  public int generateValidatedRandomID() throws SQLException {
    int id = generateRandomID();
    String criteria,field;

    if (tableName.equals("UserClient")) {
      criteria = "USERID="+id;
      field = "USERID";
    } else {
      criteria = "MERCID="+id;
      field = "MERCID";
    }

    boolean isValid = isEntryValid(criteria,field);
    while (!isValid) {
      id = generateRandomID();
      isValid = isEntryValid(criteria,field);
    }
    return id;
  }

  public boolean isEntryValid(String crit, String field) throws SQLException {
    Row row = getEntry(crit);
    String isValid = row.get(field);
    if (isValid.equals(null))
      return false;
    else
      return true;
  }
   
     
  public void insertEntry(Row entryRow) {
    try {
      table.putRow(entryRow);
    } catch(SQLException e) {
      LogWriter.write("accountServicesInterface",
                      "insertEntry",
                      "Exception while inserting new row",
                      e);
    }
  }
     
  public static void main(String args []) {
    accountServicesInterface ac
      = new accountServicesInterface("userClient");
    try {
      RowSet rows = ac.getAllEntries("userid>0");
    } catch(SQLException e) {
      LogWriter.write("accountServicesInterface",
                      "getEntry",
                      "Exception while executing SQL statement",
                      e);
    }
  }
}
0
Comment
Question by:blizz_ard
  • 3
4 Comments
 
LVL 92

Accepted Solution

by:
objects earned 35 total points
ID: 10856974
> Table table = db.getTable(tableName);

change that to:

table = db.getTable(tableName);
0
 
LVL 92

Expert Comment

by:objects
ID: 10856977
your existing code initialises a local var named table, instead of the table member var.
0
 
LVL 1

Expert Comment

by:KartikShah
ID: 10859693
The problem seems to be in your constructor. You current code is :

  public accountServicesInterface(String tableName) {
    db = new Database();
    Table table = db.getTable(tableName);
    this.tableName = tableName;
  }


while it should be:

  public accountServicesInterface(String tableName) {
    db = new Database();
    this.table = db.getTable(tableName);
    this.tableName = tableName;
  }


The problem here was, that you are initializing a local variable table, in your constructor, thile, you should have referenced to the variable table, which is a member variable.

This seems to be the reason for getting the NullPointerException
0
 
LVL 92

Expert Comment

by:objects
ID: 10864427
0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
runtime exception 2 50
maven module vs maven project 3 68
maven disable workspace resolution 1 37
Using jdbcTemplate.batchUpdate to improve INSERT performance 6 26
Java contains several comparison operators (e.g., <, <=, >, >=, ==, !=) that allow you to compare primitive values. However, these operators cannot be used to compare the contents of objects. Interface Comparable is used to allow objects of a cl…
In this post we will learn different types of Android Layout and some basics of an Android App.
Viewers will learn about the different types of variables in Java and how to declare them. Decide the type of variable desired: Put the keyword corresponding to the type of variable in front of the variable name: Use the equal sign to assign a v…
This tutorial will introduce the viewer to VisualVM for the Java platform application. This video explains an example program and covers the Overview, Monitor, and Heap Dump tabs.

680 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question