How to define the anonymous inner class separately from the constructor block?

For example in my codes I want method2 do the same thing as method1 The only difference is method2 uses the Factory class to create the ClosableResultSet.

import java.sql.*;

public class Demo {

    public static void main(String[] args) {
        method1();
        method2();  
    }

    static void method1() {

        Connection conn;
        try {
            conn = DriverManager.getConnection("jdbc:h2:C:/myDB", "sa", "sa");

            String sql = "select * from Customers";

            try (ClosableResultSet rs = new ClosableResultSet(conn, sql) {
                @Override
                public void handleError(SQLException e, String action) {
                    System.out.print(action + ": " + e.getMessage());       
                }               
            }) {
                while (rs.next()) {
                    System.out.print("Name: " + rs.getString("name") + "n");
                }
            }

        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }               

    }


    static void method2() {

        String sql = "select * from Customers";

        //here has the syntax errors    
        try (ClosableResultSet rs = Factory.createResultSet(sql) {
            @Override
            public void handleError(SQLException e, String action) {
                System.out.print(action + ": " + e.getMessage());           
            }               
        }) {
            while (rs.next()) {
                System.out.print("Name: " + rs.getString("name") + "n");
            }


        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }           

    }   
}



import java.sql.*;

public class Factory {
    public static ClosableResultSet createResultSet(String sql) throws SQLException {
        Connection conn = DriverManager.getConnection("jdbc:h2:C:/myDB", "sa", "sa");

        return new ClosableResultSet(conn, sql);
    }
}


import java.sql.*;

public class ClosableResultSet implements java.io.Closeable {

    private ResultSet rs;

    public ClosableResultSet(Connection conn, String sql) throws SQLException  {
        Statement stmt = conn.createStatement();
        rs = stmt.executeQuery(sql);    
    }

    public Boolean next() {
        try {
            return rs.next();
        } catch (SQLException e) {
            handleError(e, "next");
            return false;
        }
    }

    public String getString(String columnLabel) {
        try {
            return rs.getString(columnLabel);
        } catch (SQLException e) {
            handleError(e, "get " + columnLabel);
            return "";
        }
    }


    @Override
    public void close() {       
        try {
            rs.close();
        } catch (SQLException e) {
            handleError(e, "close");
        }

    }

    public void handleError(SQLException e, String action) {
        // to be override   
    }

}

I don't want to declare the anonymous inner class in the Factory class, is there any lambda expression allow me to put it in method2?

You can create another Factory method that takes a BiConsumer in addition to the String sql. Something like this:

import java.sql.*;
import java.util.function.BiConsumer;

public class Factory {

    public static ClosableResultSet createResultSet(String sql) throws SQLException {
        Connection conn = DriverManager.getConnection("jdbc:h2:C:/myDB", "sa", "sa");

        return new ClosableResultSet(conn, sql);
    }

    public static ClosableResultSet createResultSet(String sql, BiConsumer<SQLException, String> handler) throws SQLException {
        Connection conn = DriverManager.getConnection("jdbc:h2:C:/myDB", "sa", "sa");

        return new ClosableResultSet(conn, sql) {
            @Override
            public void handleError(SQLException e, String action) {
                handler.accept(e, action);
            }
        };
    }
}

And then your method2 should be:

static void method2() {

    String sql = "select * from Customers";

    try (ClosableResultSet rs = Factory.createResultSet(
            sql,
            (e, action) -> System.out.print(action + ": " + e.getMessage())
    )) {
        while (rs.next()) {
            System.out.print("Name: " + rs.getString("name") + "n");
        }

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

}

Yes, you can do something like this:

import java.sql.*;

public class Demo {

    public static void main(String[] args) {
        method1();
        method2();  
    }

    static void method1() {

        Connection conn;
        try {
            conn = DriverManager.getConnection("jdbc:h2:C:/myDB", "sa", "sa");

            String sql = "select * from Customers";

            try (ClosableResultSet rs = new ClosableResultSet(conn, sql) {
                @Override
                public void handleError(SQLException e, String action) {
                    System.out.print(action + ": " + e.getMessage());       
                }               
            }) {
                while (rs.next()) {
                    System.out.print("Name: " + rs.getString("name") + "n");
                }
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }               
    }

    static void method2() {

        String sql = "select * from Customers";

        //here has the syntax errors
        try (ClosableResultSet rs = Factory.createResultSet(
                sql, (e, action) -> System.out.print(action + ": " + e.getMessage())
        )) {
            while (rs.next()) {
                System.out.print("Name: " + rs.getString("name") + "n");
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

...

import java.sql.*;

public class Factory {
        public static ClosableResultSet createResultSet(String sql, final ErrorHandller errorHandller) throws SQLException {
        Connection conn = DriverManager.getConnection("jdbc:h2:C:/myDB", "sa", "sa");

        return new ClosableResultSet(conn, sql) {
            @Override
            public void handleError(SQLException e, String action) {
                errorHandller.handleError(e, action);
            }
        };
    }

    interface ErrorHandller {
        void handleError(SQLException e, String action);
    }
}

...

As you can see, new interface ErrorHandller was added. Also Factory::createResultSet receive instance of ErrorHandller as second argument now. And then in Demo::method2 we pass lambda as the second argument of Factory.createResultSet method.