CODEWITHSUNDEEP
javamysql
Arnab
Arnab

Reputation: 63

fetch sql records and store in a hashmap

I am working on a script which is supposed to store the entire fetched table into a hashmap. So far, I have been able to fetch the records from MySQl database, but i am unable to store and display the records from the hashmap. Please guide me to a correct code for the same.

The code so far:

public class myRow {
private int id;
private String name;
private int level;
private int m1;
private int m2;
private int m3;

// the constructor
public myRow( String n, int l,int m1, int m2, int m3) {

    this.name = n;
    this.level = l;
    this.m1 = m1;
    this.m2 = m2;
    this.m3 = m3;
}}

The main class is as follows:

public static void main(String[] args){
    Connection conn = null;
    Statement stmt1 = null;
    try{
        Class.forName("com.mysql.jdbc.Driver").newInstance();

        System.out.println("Connecting to database...\n\n");
        conn = DriverManager.getConnection(DB_URL,USER,PASS);

        stmt1 = conn.createStatement();
        Map<Integer, myRow> map = new HashMap<Integer, myRow>(0);

        try {
            String sql="SELECT * FROM recs.new_table;";
            System.out.println(sql);
            ResultSet rs = stmt1.executeQuery(sql);

            while(rs.next()){
                myRow mr = new myRow(rs.getString(2), rs.getInt(3),rs.getInt(4),rs.getInt(5),rs.getInt(6) );
                map.put(rs.getInt(1), mr);
            }

        } catch (SQLException sqle) {
            sqle.printStackTrace();
        }

        System.out.println(map);
        System.out.println(map.containsValue("mark"));
        }catch(Exception e){
        System.out.println(" ERROR :: "+e); 
    }

The table records are in the following manner: enter image description here

Upvotes: 0

Views: 3591

Answers (1)

schtever
schtever

Reputation: 3250

The code looks ok to me, except for the line:

System.out.println(map.containsValue("mark"));

This will not find the row containing mark. The containsValue relies on the object's equals method, and since you're passing a simple string, a String class object will never equal a myRow class so it will never find it.

To locate one of the rows in the map, you'll need some code like:

myRow findRowByName(String name) {
  for (myRow row : map.values()) {
    if (row.name.equals(name)) {
      return row;
    }
  }
}

Upvotes: 1

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