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Thread: How to return class instance?

  1. #1
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    Default How to return class instance?

    I have the next code:

    import java.sql.*;
     
    public class Products {
    private int ProductID;
    private String name;
    private String category;
    private Double price;
    public void setId(int ProductID) { this. ProductID = ProductID; }
    public int getId() { return this.ProductID; }
    public void setName(String name) { this.name = name; }
    public String getName() { return this.name; }
    public void setCategory(String category) { this. category = category; }
    public String getcategory () { return this.category; }
    public void setPrice(double price) { this.price = price; }
    public double getCijena() { return this.price; }
    public Products(int ProductID, String name, String category, Double price)
    {
        this.ProductID = ProductID;
        this.name = name;
        this.category = category;
        this.price = price;
      }
    public static void getFromId(int productID)
    {
    Connection conn = null;
       {
    try
        {
          Class.forName ("com.mysql.jdbc.Driver").newInstance ();
              conn = DriverManager.getConnection ("jdbc:mysql://localhost/prodaja", "root", "");
            System.out.println(conn.isClosed());
        }
    catch(Exception ex)
    { 
    System.out.println("Connection not established"); 
    }
     try
    {
     Statement st = conn.createStatement();
        st.executeQuery("select * from products WHERE ID_product="+productID);
        ResultSet rs = st.getResultSet();
        while (rs.next()) 
        {
            int IdP = rs.getInt(1);
            String Pname = rs.getString(2);
            String Pcategory = rs.getString(3);
            Double Pprice = rs.getDouble(4);
            Products p=new Products(IdP, Pname, Pcategory, Pprice);
        }
    }
       catch (SQLException s){
      System.out.println("SQL statement not executed!");
    }
     
    finally {
    try
        {
        if(conn!=null && !conn.isClosed())
            conn.close();
        System.out.println(conn.isClosed());
        }
    catch(Exception ex) { }
     
     }
    }

    Now, what I need is to make this method(getFromId) return this newly created class instance, with its fields values.
    Any suggestons?


  2. #2
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    Default Re: How to return class instance?

    I'm assuming you want to return your Products object, so all you need to do is change the method declaration from void, to a return type of Products.
    then in your method, use return p;

    E.g
    To write a method which returns a String, you would do:
    public String getString(){
       String x = "Hello World";
       return x;
    }
    Please use [highlight=Java]//code goes here...[/highlight] tags when posting your code

  3. #3
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    Default Re: How to return class instance?

    Quote Originally Posted by newbie View Post
    I'm assuming you want to return your Products object, so all you need to do is change the method declaration from void, to a return type of Products.
    then in your method, use return p;

    E.g
    To write a method which returns a String, you would do:
    public String getString(){
       String x = "Hello World";
       return x;
    }
    I tried that, but it's not working.
    I get error message saying:
    Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - missing return statement
    at sales.Product.getFromId(Product.java:158)
    at sales.Sales.main(Sales.java:18)
    Java Result: 1

    "Sales" is the name of main class, from which I call method(getFromID)

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    Default Re: How to return class instance?

    Well the answer is in the error message, " missing return statement".
    Take the String example, if you declare a method such as it returns a String, you really do need to return a String.

    If you're still having trouble, be sure to post the code snippet to which your error message is referring to.
    Please use [highlight=Java]//code goes here...[/highlight] tags when posting your code

  5. #5
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    Default Re: How to return class instance?

    Quote Originally Posted by newbie View Post
    Well the answer is in the error message, " missing return statement".
    Take the String example, if you declare a method such as it returns a String, you really do need to return a String.

    If you're still having trouble, be sure to post the code snippet to which your error message is referring to.
    Here is the code snippet (to which error message is referring to):
    class Product
    public static Product getFromId(int productID)
    {//this is the line 158//
    main class(Sales)
    Product.getFromId(1001);
    Last edited by nera1981; August 23rd, 2011 at 12:09 PM.

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    Default Re: How to return class instance?

    Your class is Products not Product
    Please use [highlight=Java]//code goes here...[/highlight] tags when posting your code

  7. #7
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    Default Re: How to return class instance?

    Quote Originally Posted by newbie View Post
    Your class is Products not Product
    It was, but I changed it to Product, because it should contain data for one product.

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    Default Re: How to return class instance?

    Cross posted at classInstanceInitalization - CodeGuru Forums

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