Exception in thread "Thread-5" java.lang.NullPointerException

Question

while running the code i am facing this error:

Exception in thread "Thread-5" java.lang.NullPointerException at 
com.example.example1.service.RecordData.run(RecordData.java:87)

This is my Program:

public class SearchParser {

public static void main(String[] args) {
    String url = "jdbc:mysql://localhost:3306/";
    String dbName = "share";
    String driver = "com.mysql.jdbc.Driver";
    String userName = "root";
    String password = "";

    try {
        List<RecordData> list = new ArrayList<RecordData>();
        Connection conn = DriverManager.getConnection(url + dbName,
                userName, password);

        Statement stmt = conn.createStatement();
        ResultSet mysqldata = stmt
                .executeQuery("select * from product_links");
        while (mysqldata.next()) {

            RecordData data = new RecordData();
            data.setId(mysqldata.getInt("id"));
            data.setDomain_name(mysqldata.getString("domain_name"));
            data.setCommon_link_name(mysqldata
                    .getString("common_link_name"));
            data.setHead_element_pattern(mysqldata
                    .getString("head_element_pattern"));
            data.setProduct_title_pattern(mysqldata
                    .getString("product_title_pattern"));
            data.setProduct_link_pattern(mysqldata
                    .getString("product_link_pattern"));
            data.setCurrent_price_pattern(mysqldata
                    .getString("current_price_pattern"));
            data.setImage_src_pattern(mysqldata
                    .getString("image_src_pattern"));
            data.setDecscription_pattern(mysqldata
                    .getString("decscription_pattern"));
            list.add(data);
        }
        for (RecordData data : list) {
            RecordData p = new RecordData();
            p.start();
        }

    } catch (Exception e) {
        System.out.print(e);
    }

}

}

It is basically a program which fetch data from database.

public class RecordData extends Thread {
    int id;
    String domain_name, common_link_name, head_element_pattern, product_title_pattern, product_link_pattern, current_price_pattern, image_src_pattern,
            decscription_pattern;
    public RecordData data;

    public RecordData() {
        this.data = data;
    }

    public long getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getDomain_name() {
        return domain_name;
    }

    public void setDomain_name(String domain_name) {
        this.domain_name = domain_name;
    }

    public String getCommon_link_name() {
        return common_link_name;
    }

    public void setCommon_link_name(String common_link_name) {
        this.common_link_name = common_link_name;
    }

    public String getHead_element_pattern() {
        return head_element_pattern;
    }

    public void setHead_element_pattern(String head_element_pattern) {
        this.head_element_pattern = head_element_pattern;
    }

    public String getProduct_title_pattern() {
        return product_title_pattern;
    }

    public void setProduct_title_pattern(String product_title_pattern) {
        this.product_title_pattern = product_title_pattern;
    }

    public String getProduct_link_pattern() {
        return product_link_pattern;
    }

    public void setProduct_link_pattern(String product_link_pattern) {
        this.product_link_pattern = product_link_pattern;
    }

    public String getCurrent_price_pattern() {
        return current_price_pattern;
    }

    public void setCurrent_price_pattern(String current_price_pattern) {
        this.current_price_pattern = current_price_pattern;
    }

    public String getImage_src_pattern() {
        return image_src_pattern;
    }

    public void setImage_src_pattern(String image_src_pattern) {
        this.image_src_pattern = image_src_pattern;
    }

    public String getDecscription_pattern() {
        return decscription_pattern;
    }

    public void setDecscription_pattern(String decscription_pattern) {
        this.decscription_pattern = decscription_pattern;
    }

    public void run() {
        System.out.println(data.domain_name);
    }
}

Sotirios Delimanolis · Accepted Answer · 2013-12-30 06:09:59Z

7

Because this

public RecordData() {
    this.data = data;
}

does absolutely nothing. You are assigning a field to itself. Since it starts of null, it also ends up null.

I don't know what you are trying to achieve, but you probably want to assign some other value to data.

public RecordData(RecordData data) {
    this.data = data;
}

edited Dec 30, 2013 at 6:09

answered Dec 30, 2013 at 5:58

Sotirios Delimanolis

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3 Comments

Sotirios Delimanolis Over a year ago

@user3013623 No, you are not. You can, by adding a RecordData parameter and invoking the constructor with a RecordData argument.

Sotirios Delimanolis Over a year ago

@user See my edit. Invoke the constructor with some RecordData argument you have in your main. You might need another constructor that doesn't have any arguments, so that you can create the objects that don't have a data value.

Sotirios Delimanolis Over a year ago

@user3013623 You're welcome. Consider accepting/upvoting answers to your questions if they helped you solve your problem.

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