first commit

Semester 1/Programming 1/Java/examples/projects/chapter03/mail-system/MailClient.ctxt

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+#BlueJ class context
+comment0.params=server\ user
+comment0.target=MailClient(MailServer,\ java.lang.String)
+comment0.text=\n\ Create\ a\ mail\ client\ run\ by\ user\ and\ attached\ to\ the\ given\ server.\n
+comment1.params=
+comment1.target=MailItem\ getNextMailItem()
+comment1.text=\n\ Return\ the\ next\ mail\ item\ (if\ any)\ for\ this\ user.\n
+comment2.params=
+comment2.target=void\ printNextMailItem()
+comment2.text=\n\ Print\ the\ next\ mail\ item\ (if\ any)\ for\ this\ user\ to\ the\ text\ \n\ terminal.\n
+comment3.params=to\ message
+comment3.target=void\ sendMailItem(java.lang.String,\ java.lang.String)
+comment3.text=\n\ Send\ the\ given\ message\ to\ the\ given\ recipient\ via\n\ the\ attached\ mail\ server.\n\ @param\ to\ The\ intended\ recipient.\n\ @param\ message\ The\ text\ of\ the\ message\ to\ be\ sent.\n
+numComments=4

Semester 1/Programming 1/Java/examples/projects/chapter03/mail-system/MailClient.java

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+/**
+ * A class to model a simple email client. The client is run by a
+ * particular user, and sends and retrieves mail via a particular server.
+ * 
+ * @author David J. Barnes and Michael Kölling
+ * @version 2016.02.29
+ */
+public class MailClient
+{
+    // The server used for sending and receiving.
+    private MailServer server;
+    // The user running this client.
+    private String user;
+
+    /**
+     * Create a mail client run by user and attached to the given server.
+     */
+    public MailClient(MailServer server, String user)
+    {
+        this.server = server;
+        this.user = user;
+    }
+
+    /**
+     * Return the next mail item (if any) for this user.
+     */
+    public MailItem getNextMailItem()
+    {
+        return server.getNextMailItem(user);
+    }
+
+    /**
+     * Print the next mail item (if any) for this user to the text 
+     * terminal.
+     */
+    public void printNextMailItem()
+    {
+        MailItem item = server.getNextMailItem(user);
+        if(item == null) {
+            System.out.println("No new mail.");
+        }
+        else {
+            item.print();
+        }
+    }
+
+    /**
+     * Send the given message to the given recipient via
+     * the attached mail server.
+     * @param to The intended recipient.
+     * @param message The text of the message to be sent.
+     */
+    public void sendMailItem(String to, String message)
+    {
+        MailItem item = new MailItem(user, to, message);
+        server.post(item);
+    }
+}

Semester 1/Programming 1/Java/examples/projects/chapter03/mail-system/MailItem.ctxt

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+#BlueJ class context
+comment0.params=from\ to\ message
+comment0.target=MailItem(java.lang.String,\ java.lang.String,\ java.lang.String)
+comment0.text=\n\ Create\ a\ mail\ item\ from\ sender\ to\ the\ given\ recipient,\n\ containing\ the\ given\ message.\n\ @param\ from\ The\ sender\ of\ this\ item.\n\ @param\ to\ The\ intended\ recipient\ of\ this\ item.\n\ @param\ message\ The\ text\ of\ the\ message\ to\ be\ sent.\n
+comment1.params=
+comment1.target=java.lang.String\ getFrom()
+comment1.text=\n\ @return\ The\ sender\ of\ this\ message.\n
+comment2.params=
+comment2.target=java.lang.String\ getTo()
+comment2.text=\n\ @return\ The\ intended\ recipient\ of\ this\ message.\n
+comment3.params=
+comment3.target=java.lang.String\ getMessage()
+comment3.text=\n\ @return\ The\ text\ of\ the\ message.\n
+comment4.params=
+comment4.target=void\ print()
+comment4.text=\n\ Print\ this\ mail\ message\ to\ the\ text\ terminal.\n
+numComments=5

Semester 1/Programming 1/Java/examples/projects/chapter03/mail-system/MailItem.java

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+/**
+ * A class to model a simple mail item. The item has sender and recipient
+ * addresses and a message string.
+ * 
+ * @author David J. Barnes and Michael Kölling
+ * @version 2016.02.29
+ */
+public class MailItem
+{
+    // The sender of the item.
+    private String from;
+    // The intended recipient.
+    private String to;
+    // The text of the message.
+    private String message;
+
+    /**
+     * Create a mail item from sender to the given recipient,
+     * containing the given message.
+     * @param from The sender of this item.
+     * @param to The intended recipient of this item.
+     * @param message The text of the message to be sent.
+     */
+    public MailItem(String from, String to, String message)
+    {
+        this.from = from;
+        this.to = to;
+        this.message = message;
+    }
+
+    /**
+     * @return The sender of this message.
+     */
+    public String getFrom()
+    {
+        return from;
+    }
+
+    /**
+     * @return The intended recipient of this message.
+     */
+    public String getTo()
+    {
+        return to;
+    }
+
+    /**
+     * @return The text of the message.
+     */
+    public String getMessage()
+    {
+        return message;
+    }
+
+    /**
+     * Print this mail message to the text terminal.
+     */
+    public void print()
+    {
+        System.out.println("From: " + from);
+        System.out.println("To: " + to);
+        System.out.println("Message: " + message);
+    }
+}

Semester 1/Programming 1/Java/examples/projects/chapter03/mail-system/MailServer.ctxt

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+#BlueJ class context
+comment0.params=
+comment0.target=MailServer()
+comment0.text=\n\ Construct\ a\ mail\ server.\n
+comment1.params=who
+comment1.target=int\ howManyMailItems(java.lang.String)
+comment1.text=\n\ Return\ how\ many\ mail\ items\ are\ waiting\ for\ a\ user.\n\ @param\ who\ The\ user\ to\ check\ for.\n\ @return\ How\ many\ items\ are\ waiting.\n
+comment2.params=who
+comment2.target=MailItem\ getNextMailItem(java.lang.String)
+comment2.text=\n\ Return\ the\ next\ mail\ item\ for\ a\ user\ or\ null\ if\ there\n\ are\ none.\n\ @param\ who\ The\ user\ requesting\ their\ next\ item.\n\ @return\ The\ user's\ next\ item.\n
+comment3.params=item
+comment3.target=void\ post(MailItem)
+comment3.text=\n\ Add\ the\ given\ mail\ item\ to\ the\ message\ list.\n\ @param\ item\ The\ mail\ item\ to\ be\ stored\ on\ the\ server.\n
+numComments=4

Semester 1/Programming 1/Java/examples/projects/chapter03/mail-system/MailServer.java

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+import java.util.ArrayList;
+import java.util.List;
+import java.util.Iterator;
+
+/**
+ * A simple model of a mail server. The server is able to receive
+ * mail items for storage, and deliver them to clients on demand.
+ * 
+ * @author David J. Barnes and Michael Kölling
+ * @version 2016.02.29
+ */
+public class MailServer
+{
+    // Storage for the arbitrary number of mail items to be stored
+    // on the server.
+    private List<MailItem> items;
+
+    /**
+     * Construct a mail server.
+     */
+    public MailServer()
+    {
+        items = new ArrayList<>();
+    }
+
+    /**
+     * Return how many mail items are waiting for a user.
+     * @param who The user to check for.
+     * @return How many items are waiting.
+     */
+    public int howManyMailItems(String who)
+    {
+        int count = 0;
+        for(MailItem item : items) {
+            if(item.getTo().equals(who)) {
+                count++;
+            }
+        }
+        return count;
+    }
+
+    /**
+     * Return the next mail item for a user or null if there
+     * are none.
+     * @param who The user requesting their next item.
+     * @return The user's next item.
+     */
+    public MailItem getNextMailItem(String who)
+    {
+        Iterator<MailItem> it = items.iterator();
+        while(it.hasNext()) {
+            MailItem item = it.next();
+            if(item.getTo().equals(who)) {
+                it.remove();
+                return item;
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Add the given mail item to the message list.
+     * @param item The mail item to be stored on the server.
+     */
+    public void post(MailItem item)
+    {
+        items.add(item);
+    }
+}

Semester 1/Programming 1/Java/examples/projects/chapter03/mail-system/README.TXT

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+Project: mail-system
+Authors: David Barnes and Michael Kölling
+
+This project is part of the material for the book
+
+   Objects First with Java - A Practical Introduction using BlueJ
+   Sixth edition
+   David J. Barnes and Michael Kölling
+   Pearson Education, 2016
+
+It is discussed in chapter 3.
+
+This project simulates a simple email system. Mail clients simulate email programs
+of different users. If you create two or more email clients, they can send messages
+to each other. (Note this this is a simulation: you cannot really send email. All
+messages are exchanged only between the email client objects in this project.)
+
+To use this project, 
+
+ - create a MailServer instance.
+ - create a MailClient instance. Here you have to pass the mail server as a 
+   parameter, and you have to make up a name for this user.
+ - create a second MailClient object with the same mail server and a different user 
+   name.
+ - Use the "sendMessage" method of a MailClient object to send a message to the 
+   other mail client.
+ - Use the "printNextMessage" method of the second mail client to receive the message.
+
+The purpose of this project is to demonstrate object interaction. It includes external
+method calls (one object calling methods of another object) and object creation
+statements.
+
+The debugger can be used to investigate these object interactions.

Semester 1/Programming 1/Java/examples/projects/chapter03/mail-system/package.bluej

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+#BlueJ package file
+dependency1.from=MailClient
+dependency1.to=MailServer
+dependency1.type=UsesDependency
+dependency2.from=MailClient
+dependency2.to=MailItem
+dependency2.type=UsesDependency
+dependency3.from=MailServer
+dependency3.to=MailItem
+dependency3.type=UsesDependency
+objectbench.height=89
+objectbench.width=766
+package.editor.height=365
+package.editor.width=658
+package.editor.x=70
+package.editor.y=80
+package.numDependencies=3
+package.numTargets=3
+package.showExtends=true
+package.showUses=true
+project.charset=UTF-8
+readme.editor.height=776
+readme.editor.width=876
+readme.editor.x=53
+readme.editor.y=24
+target1.editor.height=749
+target1.editor.width=844
+target1.editor.x=113
+target1.editor.y=40
+target1.height=60
+target1.name=MailItem
+target1.naviview.expanded=true
+target1.showInterface=false
+target1.type=ClassTarget
+target1.typeParameters=
+target1.width=100
+target1.x=400
+target1.y=220
+target2.editor.height=767
+target2.editor.width=863
+target2.editor.x=53
+target2.editor.y=60
+target2.height=60
+target2.name=MailServer
+target2.naviview.expanded=true
+target2.showInterface=false
+target2.type=ClassTarget
+target2.typeParameters=
+target2.width=100
+target2.x=90
+target2.y=160
+target3.editor.height=527
+target3.editor.width=712
+target3.editor.x=132
+target3.editor.y=79
+target3.height=60
+target3.name=MailClient
+target3.naviview.expanded=false
+target3.showInterface=false
+target3.type=ClassTarget
+target3.typeParameters=
+target3.width=100
+target3.x=250
+target3.y=80