Greg Pata

In this example, we have two producers (type 0 and 1) and one consumer. Again, the consumer waits for 50 ms and processes requests from the same type.
I thought it would be easier. The code does not end properly...

public class ProducerConsumerExample2 { static ProducerConsumerExample2 INSTANCE; public ProducerConsumerExample2(){ } public static void main(String [] args){ start( new ProducerConsumerExample2()); } public static void start( ProducerConsumerExample2 producerConsumerExample2 ) {        INSTANCE = producerConsumerExample2;        INSTANCE.run();      } private void run() { final BlockingQueue<Long> dropMs = new SynchronousQueue<Long> (); final Request queue = new Request(dropMs); (new Thread(new Consumer(queue,dropMs))).start();        (new Thread(new Producer(queue,0))).start();        try {            Thread.sleep(9L);        } catch (InterruptedException e) {}        (new Thread(new Producer(queue,1))).start();         } public class Producer implements Runnable {    private Request queue;    private int type;    public Producer(Request queue, int type) {        this.queue = queue;        this.type = type;    }    public void run() {        String importantInfo[] = {            "Mares eat oats",            "Does eat oats",            "Little lambs eat ivy",            "A kid will eat ivy too"        };        SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss.SSS");        for (int i = 0;i < importantInfo.length;i++) {            try {             queue.add(importantInfo[i], type);             System.out.format("MESSAGE OFFERED at %s: %d %s%n", sdf.format(Calendar.getInstance().getTime()), type, importantInfo[i]);             Thread.sleep(1000 * (i == 1 ? 0 : 1) + 10 * (type == 1 ? 0 : 1)); } catch (InterruptedException e1) { // TODO Auto-generated catch block e1.printStackTrace(); }        }        queue.add("DONE",type);    }     } public class Consumer implements Runnable {        private Request queue;        private BlockingQueue<Long> dropMs;        public Consumer(Request queue, BlockingQueue<Long> dropMs) {            this.queue = queue;            this.dropMs = dropMs;        }        public void run() {         SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss.SSS");         try {             for (Long ms = dropMs.take();true;ms = dropMs.take()) {             String message = queue.read(ms);             System.out.format("MESSAGE RECEIVED at %s: %s%n", sdf.format(Calendar.getInstance().getTime()), message);             if (message.contains("DONE")) break;            }            } catch (InterruptedException e) {   e.printStackTrace();            }        }    } public class Request { private ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1); private ArrayList<String> requests; private ArrayList<Integer> types; private ArrayList<Boolean> oks; private BlockingQueue<Long> dropMs; private int start; private boolean waiting; private boolean nextWaiting; private int oldType; private int nextOldType; public Request(BlockingQueue<Long> dropMs) { this.dropMs = dropMs; requests = new ArrayList<String>(); types = new ArrayList<Integer>(); oks = new ArrayList<Boolean>(); start = 0; waiting = false; nextWaiting = false; oldType = -1; nextOldType = -1; } public synchronized void add(String str, int type) { requests.add(str); types.add(type); oks.add(false); try { dropMs.put(0L); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public synchronized String read(Long ms) { boolean once = true; int startType = types.get(start); String str = Integer.toString(startType); int currentType = types.get(types.size()-1); if (ms.equals(0L)) { // signal from producer, wait for 50ms //System.out.format("%b %b oldType %d type %d%n", waiting, nextWaiting, oldType, currentType); if (!waiting) { waiting = true; oldType = currentType; // new future task to process ScheduledFuture<?> countdown = scheduler.schedule(new Runnable() {            @Override            public void run() {             try { dropMs.put(1L); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); }            }}, 50, TimeUnit.MILLISECONDS); return "waiting"; } else { if (currentType != oldType && !nextWaiting) { nextWaiting = true; nextOldType = currentType; // next future task to process ScheduledFuture<?> countdown = scheduler.schedule(new Runnable() {            @Override            public void run() {                         try { dropMs.put(1L); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); }            }}, 50, TimeUnit.MILLISECONDS); return "still waiting dif type"; } else { return "still waiting"; } } } else { // signal from itself: time to process waiting = false; if (nextWaiting) { nextWaiting = false; waiting = true; oldType = nextOldType; } // process request for (int i = start;i < requests.size();i++) { if (startType == types.get(i) && !oks.get(i)) { str += requests.get(i); oks.set(i, true); //update next request start index } else if(once && startType != types.get(i) && !oks.get(i)) { once = false; start = i; } } if (once) start = requests.size(); return str; } } } }

Thank you for your reply and your ideas, Tim.
Issues are present when requests arrive around the same time: hence, the slightly delayed processing to properly manage requests.

I do not fully control results of the processed requests so doing a callback on the requester might lead to inconsistency due to unreliable information.

Hi,

Here is a modified producer consumer example from docs.oracle.com.
The production is going to wait for consumers. Consumers will wait 50ms in the hope to get a bigger production at once. This is a working example which seems to do the job.
Question: Is there a more straightforward way to get production after a waiting time (here 50ms)?
(My solution consists of using two BlockingQueue with different behaviors.)

public class ProducerConsumerExample1 { static ProducerConsumerExample1 INSTANCE; public ProducerConsumerExample1(){ } public static void main(String [] args){ start( new ProducerConsumerExample1()); } public static void start( ProducerConsumerExample1 producerConsumerExample1 ) {        INSTANCE = producerConsumerExample1;        INSTANCE.run();      } private void run() { final ArrayBlockingQueue<String> drop = new ArrayBlockingQueue<> (4); final BlockingQueue<Long> dropMs = new SynchronousQueue<Long> ();        (new Thread(new Producer(drop, dropMs))).start();        (new Thread(new Consumer(drop, dropMs))).start(); } public class Producer implements Runnable {    private ArrayBlockingQueue<String> drop;    private BlockingQueue<Long> dropMs;    public Producer(ArrayBlockingQueue<String> drop, BlockingQueue<Long> dropMs) {        this.drop = drop;        this.dropMs = dropMs;    }    public void run() {        String importantInfo[] = {            "Mares eat oats",            "Does eat oats",            "Little lambs eat ivy",            "A kid will eat ivy too"        };        for (int i = 0;i < importantInfo.length;i++) {            try {             drop.put(importantInfo[i]);             Long ms = Calendar.getInstance().getTime().getTime();             dropMs.offer(ms, 0 , TimeUnit.MILLISECONDS); SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss.SSS");             System.out.format("MESSAGE OFFERED at %s: %s%n", sdf.format(Calendar.getInstance().getTime()), importantInfo[i]);             Thread.sleep(1000 * (i == 1 ? 0 : 1)); } catch (InterruptedException e1) { // TODO Auto-generated catch block e1.printStackTrace(); }        }        try {         drop.put("DONE");         Long ms = Calendar.getInstance().getTime().getTime();         dropMs.offer(ms, 0 , TimeUnit.MILLISECONDS); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); }    }     } public class Consumer implements Runnable {        private ArrayBlockingQueue<String> drop;        private BlockingQueue<Long> dropMs;        public Consumer(ArrayBlockingQueue<String> drop, BlockingQueue<Long> dropMs) {            this.drop = drop;            this.dropMs = dropMs;        }        public void run() {            try {             for (Long ms = dropMs.take();true;ms = dropMs.take()) {             try {                    Thread.sleep(50L);                } catch (InterruptedException e) {}             ArrayList<String> collection = new ArrayList<String>();             int response = drop.drainTo(collection);             String message = "";             for (String msg : collection) {             message += msg;             }             SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss.SSS");             System.out.format("MESSAGE RECEIVED at %s: %s%n", sdf.format(Calendar.getInstance().getTime()), message);             if (message.equals("DONE")) break;            }            } catch (InterruptedException e) {   e.printStackTrace();            }        }    } }

I tried to help you but I have never used the Scanner class. I need an answer and fast. So I google "Java Scanner how to use it".
Now I get the idea (on a side note, where is the line where the scanner is closed?) and I am confused.
What do you expect from the input? A string made of integers separated by space i.e. "1 -3 5" or directly a list of integers i.e. 1 then -3 then 5?
This expectation has to be clarified in your code.
From your code it seems you expect the user to enter integers one at a time. You tell us it does not work as expected.
Either you use a debugger in a Java IDE or you carefully read your code to imagine what the hell it is doing or you add after line 16:
System.out.format("Index: %d listInts:%d %n",i,listInts.get(i));
What do you see?

The corrected code follows. The interface version will appear as soon as PropertyChangeSupport becomes deprecated. :-)
import java.awt.GridLayout; import java.awt.event.*; import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.beans.PropertyChangeSupport; import java.util.ArrayList; import java.util.logging.Level; import java.util.logging.Logger; import javax.swing.*; import javax.swing.event.TableModelEvent; import javax.swing.event.TableModelListener; import javax.swing.table.AbstractTableModel;   public class SecondClass10 { public static final String SIZE_PROPERTY_NAME = "size"; public static final String A_COL_NAME = "A"; public static final String B_COL_NAME = "B"; public static final String C_COL_NAME = "C"; public static final String NAME_1 = "abc"; public static final String NAME_2 = "def"; public static final String NAME_3 = "ghi"; public static final String LOGGER_NAME = "Logger"; private static final SecondClass10 instance = new SecondClass10(); private static final Logger logger = Logger.getLogger(LOGGER_NAME); private final JFrame frame = new JFrame();    private final JScrollPane leftScroll = new JScrollPane();    private final JPanel mid = new JPanel( new GridLayout( 1, 2) );    private final MyModel model = new MyModel();    private final JTable table = new JTable( model);    private final Feeder feeder = new Feeder();    private final Timer feedTimer = new Timer(1000,null);        public static void main(String[] args) throws Exception    {     SwingUtilities.invokeLater( new Runnable() { @Override            public void run() { instance.run();            }        });    }        private void run() {         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);         model.addRow(NAME_1);         model.addRow(NAME_2);         model.addRow(NAME_3);         model.addTableModelListener(new TableModelListener() {              public void tableChanged(TableModelEvent e) {                  if (e.getType() == TableModelEvent.UPDATE) {                      int col = e.getColumn();                      int row = e.getLastRow();                      logger.log(Level.INFO,"row: " + row + " col: " + col);                  }              }            });         leftScroll.setViewportView(table);         mid.add(leftScroll);         frame.add(mid);               frame.pack();         frame.setVisible(true);         feedTimer.start();    }            private final class MyModel extends AbstractTableModel implements PropertyChangeListener{        private ArrayList<MyRow> rows = new ArrayList<MyRow>();                public MyRow getMyRow(int i)  {            return rows.get(i);        }                public void addRow( String description) {            MyRow row = new MyRow( rows.size(), description );            logger.log(Level.INFO, String.format("Adding row at index %d %n", rows.size()));            rows.add( row);            TableActionListener tal = new TableActionListener(description, row, SecondClass10.instance.feeder);            SecondClass10.instance.feedTimer.addActionListener(tal);            fireTableRowsInserted( rows.size() - 1, rows.size() - 1);            row.addPropertyChangeListener(this);        }                public void updateIndexing(int position) {         for (int i = position; i < getRowCount(); i++)            {                rows.get(i).index = i;            }        }                @Override public void propertyChange(PropertyChangeEvent e) {         if (e.getSource() instanceof MyRow) {         MyRow row = (MyRow) e.getSource();         fireTableRowsUpdated(row.index, row.index);         } }              @Override public int getRowCount() {            return rows.size();        }                @Override public int getColumnCount() {            return 3;        }                @Override public String getColumnName(int col) {            switch( col) {                case 0: return A_COL_NAME;                case 1: return B_COL_NAME;                case 2: return C_COL_NAME;                default: throw new IndexOutOfBoundsException();            }        }        @Override public Object getValueAt(int rowIn, int col) {            MyRow row = rows.get( rowIn);            switch( col) {                case 0: return row.description;                case 1: return row.colBsize;                case 2: return row.colCsize;                default: throw new IndexOutOfBoundsException();            }        }    }        private final static class MyRow {         private PropertyChangeSupport pcs = new PropertyChangeSupport(this);         private int index;         private String description;            private int colBsize;            private int colCsize;                        public MyRow( int index, String description) {                this.index = index;             this.description = description;            }                        public int getCellValue(int col){                switch(col){                    case 1: return colBsize;                    case 2: return colCsize;                    default: throw new IndexOutOfBoundsException();                }            }                        public void setSize( String sizeType, int size) {                switch( sizeType) {                    case B_COL_NAME:                        colBsize = size;                        break;                    case C_COL_NAME:                        colCsize = size;                        break;                }                pcs.firePropertyChange(SIZE_PROPERTY_NAME, null, size );                      }                        public void addPropertyChangeListener(PropertyChangeListener listener) {     pcs.addPropertyChangeListener(listener);     }        }                private final class TableActionListener implements ActionListener {            private String description;            private MyRow row;            private Feeder feeder;                        public TableActionListener(String description, MyRow row, Feeder feeder){                this.description = description;                this.row = row;                this.feeder = feeder;            }                        @Override            public void actionPerformed(ActionEvent event) {                                if (description.equals( feeder.generator(0)))                    row.setSize(feeder.generator(1), Integer.parseInt(feeder.generator(2)));                                }        }                public final static class Feeder {            private int count;                        public Feeder(){                count = 0;            }                        public String generator(int col) {                String[] descriptions = {NAME_1, NAME_2, NAME_3};                String[] sizeTypes = {B_COL_NAME, C_COL_NAME};                int n1 = ++count % 3;                int n2 = (count % 7) % 2;                int n3 = (count % 11) % 10;                switch ( col) {                    case 0: return descriptions[n1];                    case 1: return sizeTypes[n2];                    case 2: return Integer.toString(n3);                    default: throw new IndexOutOfBoundsException();                  }            }        } }  

Thank you very much Stephan! Brilliant!
I appreciate. It is not as simple as I thought.

Thank you Tim for your suggestion.

Tim Moores wrote:Why an interface?

This is what is suggested here by Stephan.
It could be simple in my test code but I don't know how to do it.

Thank you Stephan for your time.

You are right. I will improve the code as you suggest.

The main question is: how to use an interface to replace the deprecated Observer/Observable or propertyChangeSupport/PropertyChangeListener?

Hi,

Long story short: the  upgrade of my computer has meant the swap from Oracle JDK to OpenJDk version 15 and Observer/Observable have been declared deprecated!
In the following code (inspired from the last version found in this thread) I just want the rows of the table to be updated.

So, I replace Observer/Observable with PropertyChangeListener/PropertyChangeSupport. It runs as expected.

By curiosity I would like to know how to do it with the use of an interface. Any hint?

On a side note, in class MyRow, m_rank tracks the rank of the row in the ArrayList to avoid looking for it in a loop (see the previous code above). Is there a straightforward way to do it without the use of the explicit member m_rank?

Thank you for your help,
Greg

import java.awt.GridLayout; import java.awt.event.*; import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.beans.PropertyChangeSupport; import java.util.ArrayList; import javax.swing.*; import javax.swing.event.TableModelEvent; import javax.swing.event.TableModelListener; import javax.swing.table.AbstractTableModel;   public class SecondClass10 {    static SecondClass10 INSTANCE = new SecondClass10();    private final JFrame m_frame = new JFrame();    private final JScrollPane leftScroll = new JScrollPane();    private final JPanel mid = new JPanel( new GridLayout( 1, 2) );    final MyModel m_model = new MyModel();    final MyTable m_table = new MyTable( m_model);    private final Feeder m_feeder = new Feeder();    private Timer m_t = new Timer(1000,null);        public static void main(String[] args) throws Exception    {        INSTANCE.run();    }        private void run() {             m_frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);         m_model.addRow("Abc");         m_model.addRow("Def");         m_model.addRow("Ghi");         m_model.addTableModelListener(new TableModelListener() {              public void tableChanged(TableModelEvent e) {                  if (e.getType() == TableModelEvent.UPDATE) {                      int col = e.getColumn();                      int row = e.getLastRow();                      System.out.println("row: " + row + " col: " + col);                  }              }            });         leftScroll.setViewportView(m_table);         mid.add(leftScroll);         m_frame.add(mid);               m_frame.pack();         m_frame.setVisible(true);         m_t.start();    }                class MyTable extends JTable {                  public MyTable(MyModel model) {            super( model);        }    }              class MyModel extends AbstractTableModel implements PropertyChangeListener{        private ArrayList<MyRow> m_rows = new ArrayList<MyRow>();                public ArrayList<MyRow> getRows() {            return m_rows;        }        void addRow( String description) {            MyRow row = new MyRow( m_rows.size(), description );            System.out.format("Adding row at rank %d %n", m_rows.size());            m_rows.add( row);            TableActionListener tal = new TableActionListener(description, row, SecondClass10.INSTANCE.m_feeder);            SecondClass10.INSTANCE.m_t.addActionListener(tal);            fireTableRowsInserted( m_rows.size() - 1, m_rows.size() - 1);            row.addPropertyChangeListener(this);        }                public void updateRanking() {         for (int i = 0; i < getRowCount(); i++)            {                m_rows.get(i).m_rank = i;            }        }                @Override public void propertyChange(PropertyChangeEvent e) {         if (e.getSource() instanceof MyRow) {         MyRow row = (MyRow) e.getSource();         fireTableRowsUpdated(row.m_rank, row.m_rank);         } }                @Override public int getRowCount() {            return m_rows.size();        }                @Override public int getColumnCount() {            return 3;        }                @Override public String getColumnName(int col) {            switch( col) {                case 0: return "A";                case 1: return "B";                case 2: return "C";                default: return null;            }        }        @Override public Object getValueAt(int rowIn, int col) {            MyRow row = m_rows.get( rowIn);            switch( col) {                case 0: return row.m_A;                case 1: return row.m_B;                case 2: return row.m_C;                default: return null;            }        }    }        static class MyRow {         private PropertyChangeSupport propertyChangeSupport = new PropertyChangeSupport(this);         int m_rank;         String m_A;            int m_B;            int m_C;                        MyRow( int rank, String description) {                m_rank = rank;             m_A = description;            }                        public int getSize(int col){                switch(col){                    case 1: return m_B;                    case 2: return m_C;                    default: return -1;                }            }                        public void setSize( String sizeType, int size) {                switch( sizeType) {                    case "B":                        m_B = size;                        break;                    case "C":                        m_C = size;                        break;                }                propertyChangeSupport.firePropertyChange("size", null, size );                      }                        public void addPropertyChangeListener(PropertyChangeListener listener) {     propertyChangeSupport.addPropertyChangeListener(listener);     }        }                private class TableActionListener implements ActionListener {            private String description;            private MyRow row;            private Feeder feeder;                        public TableActionListener(String description, MyRow row, Feeder feeder){                this.description = description;                this.row = row;                this.feeder = feeder;            }                        @Override            public void actionPerformed(ActionEvent event) {                                if (description.equals( feeder.generator(1)))                    row.setSize(feeder.generator(2), Integer.parseInt(feeder.generator(3)));                                }        }                public class Feeder {            private int m_salt;                        public Feeder(){                m_salt = 0;            }                        public String generator(int col) {                String[] descriptions = {"Abc", "Def", "Ghi"};                String[] sizeTypes = {"B", "C"};                int n1 = ++m_salt % 3;                int n2 = (m_salt % 7) % 2;                int n3 = (m_salt % 11) % 10;                switch ( col) {                    case 1: return descriptions[n1];                    case 2: return sizeTypes[n2];                    case 3: return Integer.toString(n3);                    default: return null;                  }            }        } }

Great example! In the above code, RADIUS should have been named DIAMETER.

Tony Docherty wrote:The ZRow class needs to have a public no args constructor.

Indeed, thank you Tony.

Hi,
It seems I am not able to serialize an ArrayList<NonTrivialObject>() to xml...
Here is the debug code:
public class ZRow { private int age; public ZRow(String name, double weight, int age){ this.age = age; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public void printout(){ System.out.format("age %d%n", age); } }
import java.io.Serializable; import java.util.ArrayList; public class ZBean implements Serializable{ private static final long serialVersionUID = 5L; private ArrayList<ZRow> zRows = new ArrayList<ZRow>() ; public ZBean() {} public ArrayList<ZRow> getZRows() {return zRows;} public void setZRows(ArrayList<ZRow> zRows) {this.zRows = zRows;} public void printout(){ for(ZRow zrow : zRows){ zrow.printout(); } } }
import java.beans.XMLEncoder; import java.io.BufferedOutputStream; import java.io.FileOutputStream; import java.util.ArrayList; public class Zgroup { private String zFileName = "zLast.xml"; private ArrayList<ZRow> rows = new ArrayList<ZRow>(); public Zgroup(){} public ArrayList<ZRow> getRows() { return rows; } public void setRows(ArrayList<ZRow> rows) { this.rows = rows; } public static void main(String[] args) { Zgroup zg = new Zgroup(); zg.test(); } public void test(){ rows.add(new ZRow("Ali", 1.0, 2)); rows.add(new ZRow("Bli", 2.0, 3)); serializeToXml(); } public void serializeToXml(){ try { ZBean zb = new ZBean(); zb.setZRows(rows); zb.printout(); FileOutputStream fos = new FileOutputStream(zFileName, false); XMLEncoder xmlEncoder = new XMLEncoder(new BufferedOutputStream(fos)); xmlEncoder.writeObject(zb); xmlEncoder.close(); } catch (Exception e) { System.out.println(e.getMessage()); } } }
The output is:
age 2 age 3 java.lang.InstantiationException: com.ac.derivatives.ZRow ...

I do not know how to correct this.

Thank you for your help.

Sresh Rangi wrote:This can be done with the newer CompletableFuture class.

Good to know. Thank you.

Thank you, Chris, for your help!
1) Ok you are right.
2) I have tried and failed. But now, thanks to you it works . The code follows:
(slightly different from what you described)
public class Postman{ private boolean msgArrived; private long msg; ... public synchronized void notifyMsgArrived(){ msgArrived = true; notifyAll(); } public synchronized void checkout(){ // A-thread begins msgArrived = false; Test.controller.requestData( new IDataHandler() { @Override public void retrieveData(long data) { // B-thread retrieves data msg = data; notifyMsgArrived(); } }); while(!msgArrived){ try { wait(); } catch (InterruptedException ie) { return; } } System.out.format("The message is %d %n", msg); }

Hi,
Here is the code of a kind of client/server communication. It works.
However I am sure there is a better way to notify the client as soon as the message arrives.
Thank you for your help.
public class Postman{ private boolean msgArrived; private long msg; ... public void checkout(){ // A-thread begins msgArrived = false; Test.controller.requestData( new IDataHandler() { @Override public void retrieveData(long data) { // B-thread retrieves data msg = data; // B-thread already exists and still exists // after the end of A-thread msgArrived = true; } }); while(!msgArrived){ try { Thread.sleep(250); } catch (InterruptedException ie) { return; } } System.out.format("The message is %d %n", msg); }