encryption - Exporting/Import Encrypted Code Java -

i trying export encoded text txt file. somewhere in export , import goes wrong. during same application can export , import fine. encode , decode. when close application , run again import encoded text, input changes wasn't, , throws off decryption.

i believe may have cipher being randomly generated every time application run. not know how fix it.

warning. application vary big. i'm sorry that.

package crypt;  import java.awt.borderlayout; import java.awt.flowlayout; import java.awt.event.actionevent; import java.awt.event.actionlistener; import java.io.file; import java.io.filenotfoundexception; import java.io.printwriter; import java.io.unsupportedencodingexception; import java.security.invalidkeyexception; import java.security.key; import java.security.nosuchalgorithmexception; import java.security.securerandom; import java.util.scanner;  import javax.crypto.badpaddingexception; import javax.crypto.cipher; import javax.crypto.illegalblocksizeexception; import javax.crypto.nosuchpaddingexception; import javax.crypto.spec.secretkeyspec; import javax.swing.jbutton; import javax.swing.jfilechooser; import javax.swing.jframe; import javax.swing.jlabel; import javax.swing.jmenu; import javax.swing.jmenubar; import javax.swing.jmenuitem; import javax.swing.joptionpane; import javax.swing.jpanel; import javax.swing.jscrollpane; import javax.swing.jtextarea; import javax.swing.jtextfield;  /**  * program imports exports encrypts , decrypts text file.  * known bugs can't reuse exported , imported files  * outside of current application session.  * may cause cipher having different random values in place  * when restarts program. 2 ciphers never same.  * encryption application impossible decrypt.  * yet lack of being able reuse same cipher on 2 applications  * program useless.  * @author qward  *  */ @suppresswarnings("serial") public class crypt extends jframe {      final private cipher cipher = cipher.getinstance("aes");      /**      * @throws nosuchalgorithmexception      * @throws nosuchpaddingexception      */     public crypt() throws nosuchalgorithmexception, nosuchpaddingexception {         super("cypt");         setdefaultcloseoperation(jframe.exit_on_close);         setsize(600, 600);         setlocationrelativeto(null);         setresizable(false);          // sets 1 cipher encode , decode          // initiating components         jfilechooser filechooser = new jfilechooser();         filechooser.setcurrentdirectory(new file(system                 .getproperty("user.home")));         jpanel left = new jpanel();         jpanel right = new jpanel();         jpanel bottom = new jpanel();         jpanel top = new jpanel();         left.setlayout(new borderlayout());         right.setlayout(new borderlayout());         bottom.setlayout(new flowlayout());         top.setlayout(new flowlayout());         jlabel inputlabel = new jlabel("input");         jlabel outputlabel = new jlabel("output");         jbutton generatekey = new jbutton("generate key");         final jtextarea input = new jtextarea(20, 25);         final jtextarea output = new jtextarea(20, 25);         jscrollpane inputscroll = new jscrollpane(input);         jscrollpane outputscroll = new jscrollpane(output);         final jtextfield key = new jtextfield(20);         jbutton encode = new jbutton("encode");         jbutton decode = new jbutton("decode");         jbutton swap = new jbutton("swap");         jmenubar bar = new jmenubar();         jmenu file = new jmenu("file");         jmenuitem export = export(filechooser, output);         jmenuitem imports = imports(filechooser, input);         file.add(imports);         file.add(export);         bar.add(file);          // position components         bottom.add(generatekey);         bottom.add(key);         bottom.add(encode);         bottom.add(decode);         top.add(swap);         left.add(inputscroll, borderlayout.center);         left.add(inputlabel, borderlayout.north);         right.add(outputscroll, borderlayout.center);         right.add(outputlabel, borderlayout.north);         add(left, borderlayout.west);         add(right, borderlayout.east);         add(bottom, borderlayout.south);         add(top, borderlayout.north);         setjmenubar(bar);          // add events buttons         encode.addactionlistener(new actionlistener() {             @override             public void actionperformed(actionevent arg0) {                 if (key.gettext().length() == 16) {                     output.settext(encrypt(input.gettext(), new secretkeyspec(                             key.gettext().getbytes(), "aes"), cipher));                 } else {                     joptionpane.showmessagedialog(null,                             "please input valid 16 character key");                 }             }         });         generatekey.addactionlistener(new actionlistener() {             @override             public void actionperformed(actionevent arg0) {                 key.settext(generatekey());             }         });         decode.addactionlistener(new actionlistener() {             @override             public void actionperformed(actionevent arg0) {                 if (key.gettext().length() == 16) {                     output.settext(decrypt(input.gettext(), new secretkeyspec(                             key.gettext().getbytes(), "aes"), cipher));                 } else {                     joptionpane.showmessagedialog(null,                             "please input valid 16 character key");                 }             }         });         swap.addactionlistener(new actionlistener() {             @override             public void actionperformed(actionevent arg0) {                 string temp = input.gettext();                 input.settext(output.gettext());                 output.settext(temp);             }         });          // begin         pack();         setvisible(true);     }      /**      * @param filechooser      * @param output      * @return      */     private jmenuitem export(final jfilechooser filechooser,             final jtextarea output) {         jmenuitem export = new jmenuitem("export");         export.addactionlistener(new actionlistener() {             @override             public void actionperformed(actionevent arg0) {                 int result = filechooser.showopendialog(crypt.this);                 if (result == jfilechooser.approve_option) {                     file selectedfile = filechooser.getselectedfile();                     if (selectedfile.getname().tolowercase().endswith(".txt")) {                         printwriter out = null;                         try {                             out = new printwriter(selectedfile                                     .getabsolutepath());                             out.print(new string(cipher.dofinal(output                                     .gettext().getbytes())));                         } catch (filenotfoundexception                                 | illegalblocksizeexception                                 | badpaddingexception e) {                             out.print(output.gettext());                         } {                             out.close();                         }                     } else {                         joptionpane.showmessagedialog(null,                                 "please select .txt file");                     }                 }             }         });         return export;     }      /**      * @param filechooser      * @param input      * @return      */     private jmenuitem imports(final jfilechooser filechooser,             final jtextarea input) {         jmenuitem imports = new jmenuitem("import");         imports.addactionlistener(new actionlistener() {             @override             public void actionperformed(actionevent arg0) {                 int result = filechooser.showopendialog(crypt.this);                 if (result == jfilechooser.approve_option) {                     file selectedfile = filechooser.getselectedfile();                     if (selectedfile.getname().tolowercase().endswith(".txt")) {                         scanner in = null;                         try {                             in = new scanner(new file(selectedfile                                     .getabsolutepath()));                             string str = "";                             while (in.hasnextline()) {                                 str += in.nextline() + "\n";                             }                             byte[] encrypted = cipher.dofinal(input.gettext()                                     .getbytes());                             input.settext(new string(encrypted, "iso-8859-1"));                         } catch (exception e) {                             try {                                 in = new scanner(new file(selectedfile                                         .getabsolutepath()));                                 string str = "";                                 while (in.hasnextline()) {                                     str += in.nextline() + "\n";                                 }                                 input.settext(new string(str));                             } catch (filenotfoundexception e1) {                                 // todo auto-generated catch block                                 e1.printstacktrace();                             }                         } {                             in.close();                         }                     } else {                         joptionpane.showmessagedialog(null,                                 "please select .txt file");                     }                 }             }         });         return imports;     }      /**      * @return      */     private string generatekey() {         try {             securerandom random = new securerandom();             return new string(random.generateseed(16), "iso-8859-1");         } catch (unsupportedencodingexception u) {          }         return "";     }      /**      * @param input      * @param key      * @param cipher      * @return      */     private string encrypt(string input, key key, cipher cipher) {          try {             // encrypt text             cipher.init(cipher.encrypt_mode, key);             byte[] encrypted = cipher.dofinal(input.getbytes());              return new string(encrypted, "iso-8859-1");         } catch (exception e) {             e.printstacktrace();         }         return "";     }      /**      * @param input      * @param key      * @param cipher      * @return      */     private string decrypt(string input, key key, cipher cipher) {         try {             // decrypt text             cipher.init(cipher.decrypt_mode, key);             string decrypted = new string(cipher.dofinal(input                     .getbytes("iso-8859-1")));              return decrypted;         } catch (exception e) {             e.printstacktrace();         }         return "";     }      /**      * @param args      * @throws nosuchalgorithmexception      * @throws nosuchpaddingexception      * @throws invalidkeyexception      */     public static void main(string[] args) throws nosuchalgorithmexception,             nosuchpaddingexception, invalidkeyexception {         new crypt();     } } 

here randomness comes from. may want save
whatever method returns , use on next run of app.

/**  * @return  */ private string generatekey() {     try {         securerandom random = new securerandom();         return new string(random.generateseed(16), "iso-8859-1");     } catch (unsupportedencodingexception u) {      }     return ""; } 

so think how rework if want app behave ok
1 run other. also, don't use empty catch blocks ever.