Searching from the Processing.org site (as opposed as this forum only) can lead to some existing solutions:
https://www.google.com/search?as_sitesearch=processing.org&as_q=copy+paste+clipboard

thank you PhiLho I fount this code 

The code below is taken from the G4P library and is used to copy and paste text to/from the system clipboard.

It is very easy to use. In your sketch create a new (Java not pde) tab called GClip.java ( the spelling of the tab is important since it must match the name of the class including upper / lowercase)

Copy and paste the code at the end of this post into the new tab and save it.

Using it is simplicity, in your main pde tab copy and paste this example. When you run the sketch the conyents of n1 is copy and pasted into n2 and then n2 is printed out.

1. String n1, n2;
2. // String to copy to clipboard
3. n1 = "Harry Potter";
4. // Copy to clipboard
5. GClip.copy(n1);
6. // Get clipboard contents into another string
7. n2 = GClip.paste();
8. // Display new string
9. println(n2);

GClip.java

1. /*
2.   Part of the GUI for Processing library
3.      http://www.lagers.org.uk/g4p/index.html
4.      http://gui4processing.googlecode.com/svn/trunk/
5.  
6.       Copyright (c) 2008-09 Peter Lager
7.  
8.  The actual code to create the clipbaord, copy and paste were
9.  taken taken from a similar GUI library Interfascia ALPHA 002 --
10.  http://superstable.net/interfascia/  produced by Brenden Berg
11.  The main change is to provide static copy and paste methods to
12.  separate the clipboard logic from the component logic and provide
13.  global access.
14.  
15.  This library is free software; you can redistribute it and/or
16.  modify it under the terms of the GNU Lesser General Public
17.  License as published by the Free Software Foundation; either
18.  version 2.1 of the License, or (at your option) any later version.
19.  
20.  This library is distributed in the hope that it will be useful,
21.  but WITHOUT ANY WARRANTY; without even the implied warranty of
22.  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
23.  Lesser General Public License for more details.
24.  
25.  You should have received a copy of the GNU Lesser General
26.  Public License along with this library; if not, write to the
27.  Free Software Foundation, Inc., 59 Temple Place, Suite 330,
28.  Boston, MA  02111-1307  USA
29.  */
30. 
    
31. import java.awt.Toolkit;
32. import java.awt.datatransfer.Clipboard;
33. import java.awt.datatransfer.ClipboardOwner;
34. import java.awt.datatransfer.DataFlavor;
35. import java.awt.datatransfer.StringSelection;
36. import java.awt.datatransfer.Transferable;
37. 
    
38. /*
39.  * I wanted to implement copying and pasting to the clipboard using static
40.  * methods to simplify the sharing of a single clipboard over all classes.
41.  * The need to implement the ClipboardOwner interface requires an object so
42.  * this class creates an object the first time an attempt to copy or paste
43.  * is used.
44.  *
45.  * All methods are private except copy() and paste() - lostOwnership()
46.  * has to be public because of the Clipboard owner interface.
47.  *
48.  * @author Peter Lager
49.  *
50.  */
51. 
    
52. /**
53.  * This provides clipboard functionality for text and is currently only used by the
54.  * GTextField class.
55.  *
56.  * @author Peter Lager
57.  */
58. public class GClip implements ClipboardOwner {
59.   /**
60.    * Static reference to enforce singleton pattern
61.    */
62.   private static GClip gclip = null;
63. 
    
64.   /**
65.    * Class attribute to reference the programs clipboard
66.    */
67.   private Clipboard clipboard = null;
68. 
    
69.   /**
70.    * Copy a string to the clipboard
71.    * @param chars
72.    */
73.   public static boolean copy(String chars) {
74.     if (gclip == null)
75.       gclip = new GClip();
76.     return gclip.copyString(chars);
77.   }
78. 
    
79.   /**
80.    * Get a string from the clipboard
81.    * @return the string on the clipboard
82.    */
83.   public static String paste() {
84.     if (gclip == null)
85.       gclip = new GClip();
86.     return gclip.pasteString();
87.   }
88. 
    
89.   /**
90.    * Ctor is private so clipboard is only created when a copy or paste is
91.    * attempted and one does not exist already.
92.    */
93.   private GClip() {
94.     if (clipboard == null) {
95.       makeClipboardObject();
96.     }
97.   }
98. 
    
99.   /**
100.    * If security permits use the system clipboard otherwise create
101.    * our own application clipboard.
102.    */
103.   private void makeClipboardObject() {
104.     SecurityManager security = System.getSecurityManager();
105.     if (security != null) {
106.       try {
107.         security.checkSystemClipboardAccess();
108.         clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
109.       }
110.       catch (SecurityException e) {
111.         clipboard = new Clipboard("Application Clipboard");
112.       }
113.     }
114.     else {
115.       try {
116.         clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
117.       }
118.       catch (Exception e) {
119.         // THIS IS DUMB - true but is there another way - I think not
120.       }
121.     }
122.   }
123. 
     
124.   /**
125.    * Copy a string to the clipboard. If the Clipboard has not been created
126.    * then create it.
127.    * @return true for a successful copy to clipboard
128.    */
129.   private boolean copyString(String chars) {
130.     if (clipboard == null)
131.       makeClipboardObject();
132.     if (clipboard != null) {
133.       StringSelection fieldContent = new StringSelection (chars);
134.       clipboard.setContents (fieldContent, this);
135.       return true;
136.     }
137.     return false;
138.   }
139. 
     
140.   /**
141.    * Gets a string from the clipboard. If there is no Clipboard
142.    * then create it.
143.    * @return
144.    */
145.   private String pasteString() {
146.     // If there is no clipboard then there is nothing to paste
147.     if (clipboard == null) {
148.       makeClipboardObject();
149.       return "";
150.     }
151.     // We have a clipboard so get the string if we can
152.     Transferable clipboardContent = clipboard.getContents(this);
153.     if ((clipboardContent != null) &&
154.       (clipboardContent.isDataFlavorSupported(DataFlavor.stringFlavor))) {
155.       try {
156.         String tempString;
157.         tempString = (String) clipboardContent.getTransferData(DataFlavor.stringFlavor);
158.         return tempString;
159.       }
160.       catch (Exception e) {
161.         e.printStackTrace ();
162.       }
163.     }
164.     return "";
165.   }
166. 
     
167.   /**
168.    * Reqd by ClipboardOwner interface
169.    */
170.   public void lostOwnership(Clipboard clipboard, Transferable contents) {
171.   }
172. }