user interface - Java reading and writing ArrayList type Contact to GUI -
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i've made several corrections , able compile. when attempting add contact file receive null pointer exception @ line 13 of contactscollection class:
for (int = 0; < contactlist.size(); i++) and line 93 of contacts (gui) class:
contactlist.add(contact); contacts class:
import java.util.*; import java.io.*; public class contact implements serializable { public static final long serialversionuid = 42l; public string name, number; contact() { name = "no name"; number = "no number"; } contact (string thename, string thenumber) { this.name = thename; this.number = thenumber; } public void setname(string aname) { this.name = aname; } public void setnumber(string anumber) { this.number =anumber; } public string getname() { return name; } public string getnumber() { return number; } public string tostring() { return name + ": " + number; } public boolean equals(contact other) { if (name.equals(other.getname()) && number.equals(other.getnumber())) { return(true); } else { return(false); } } } contacts collection class
import java.io.*; import java.util.*; class contactscollection { public static arraylist<contact> contactlist; public static void write() { try { objectoutputstream out = new objectoutputstream(new fileoutputstream("contactlist.dat")); (int = 0; < contactlist.size(); i++) { out.writeobject(contactlist.get(i)); } out.close(); } catch(ioexception e) { e.printstacktrace(); } } public static void read() { contactlist = new arraylist<contact>(); try { objectinputstream in = new objectinputstream(new fileinputstream("contactlist.dat")); contact temp; while (in.available()!=0) { temp = (contact)in.readobject(); contactlist.add(temp); } in.close(); } catch(filenotfoundexception e) { e.printstacktrace(); } catch(ioexception e) { e.printstacktrace(); } catch(classnotfoundexception e) { e.printstacktrace(); } } } contacts (gui) class
import java.awt.*; import javax.swing.*; import java.awt.event.*; import javax.swing.timer; import java.util.*; class contacts extends jframe implements actionlistener, windowlistener { public static final int width = 400; public static final int height = 600; public static final int small_width = 200; public static final int small_height = 100; private static final dimension stdbtn = new dimension(150, 50); jpanel centerpanel, northpanel, southpanel; imageicon icon; jlabel picture; jbutton addcontact, displaycontacts; jscrollpane scroll; jtextarea textarea; clock clock; background background; contact contact; arraylist<contact> contactlist; public contacts() { super("contacts"); this.setlayout(new borderlayout()); this.setsize(width, height); this.setdefaultcloseoperation(jframe.do_nothing_on_close); addwindowlistener(this); this.setlocationrelativeto(null); centerpanel = new jpanel(); northpanel = new jpanel(); southpanel = new jpanel(); centerpanel.setbackground(color.black); southpanel.setbackground(color.black); clock = new clock(); northpanel.add(clock); icon = new imageicon("contactsbackground.jpg"); picture = new jlabel(icon); centerpanel.add(picture); textarea = new jtextarea("", 10, 30); textarea.seteditable(false); jscrollpane scroll = new jscrollpane(textarea, jscrollpane.vertical_scrollbar_always, jscrollpane.horizontal_scrollbar_as_needed); centerpanel.add(scroll); jbutton displaycontacts = new jbutton("display contacts"); displaycontacts.addactionlistener(this); southpanel.add(displaycontacts); jbutton addcontact = new jbutton("add contact"); addcontact.addactionlistener(this); southpanel.add(addcontact); this.add(northpanel, borderlayout.north); this.add(centerpanel, borderlayout.center); this.add(southpanel, borderlayout.south); setresizable(false); } public void actionperformed(actionevent e) { contactlist = new arraylist<contact>(); jbutton source = (jbutton)e.getsource(); string contactinput = source.gettext(); if (contactinput == "display contacts") { contactscollection.read(); (int = 0; < contactlist.size(); i++) { contact = (contact)contactlist.get(i); textarea.settext(contact.getname() + "," + contact.getnumber() + "\n"); } } if (contactinput == "add contact") { string name = joptionpane.showinputdialog(null, "enter name"); string number = joptionpane.showinputdialog(null, "enter number"); contact = new contact(name, number); contactlist.add(contact); contactscollection.write(); } } public void windowopened(windowevent e) {} public void windowclosing(windowevent e) { this.setvisible(false); background = new background(); background.setvisible(true); } public void windowclosed(windowevent e) {} public void windowiconified(windowevent e) {} public void windowdeiconified(windowevent e) {} public void windowactivated(windowevent e) {} public void windowdeactivated(windowevent e) {} }
regarding
the first error i'm running "cannot find symbol method read()" , "cannot find symbol method write()".
you're calling method on arraylist, read(), doesn't exist. need call method on 1 of contents of arraylist, not arraylist itself. it's trying make omelette egg crate -- won't work. need use egg or 2 instead. same thing write().
regarding
the second error in action listener display contacts stating "an array required contact found".
you should tell line causes error.
edit
show:
for (int = 0; < contactlist.size(); i++) { textarea.settext(contact[i].getname() + "," + contact [i].getnumber() + "\n"); } that code makes no sense. need use list variable, contactlist , item via arraylist get(...) method.
your code suggests you're blindly adding bunch of code regardless of errors, , won't work. if can't use ide, should compile often, after each 1-3 lines , fix compilation errors before trying add more code. else you'll end rat's nest of errors. also, read manual/book. don't guess @ stuff.
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