java - Radio Button Project with null point errors -

how fix it?

-------------------configuration: questions - jdk version 1.8.0_25 - -------------------- exception in thread "main" java.lang.nullpointerexception @ question3.(question3.java:103) @ question2.(question2.java:51) @ questions.main(questions.java:17)

//////////////\ output of whole program

hey need project, don't know how fix it. i'm new @ this, in advance helping.

this first class, named questions

/**   * @(#)questions.java   *   * questions application   *   * @author    * @version 1.00 2015/5/22   */  import java.awt.*;  import java.awt.event.*;  import javax.swing.*;     public class questions {            public static void main(string[] args) {      	      	question2 frame = new question2();      	frame.setsize(800,600);      	frame.setvisible(true);      }  }

this 2nd class, name question2

/**   * @(#)question2.java   *   *   * @author    * @version 1.00 2015/5/22   */  import java.awt.*;  import java.awt.event.*;  import javax.swing.*;    public class question2 extends jframe {  	  	private jpanel buttonpanel;        public question2() {      	jmenubar menubar=new jmenubar();      	jmenu menu=new jmenu();      	jmenuitem fileexit=new jmenuitem();      	jmenuitem reset=new jmenuitem();      	setjmenubar(menubar);      	menu.settext("file");      	fileexit.settext("reset");      	      	menu.add(fileexit);      	menu.add(fileexit);      	menubar.add(menu);      	      	settitle("how use radio buttons");      	      	reset.addactionlistener(new resetlistener());      	      	fileexit.addactionlistener(      		new actionlistener (){      			public void actionperformed(actionevent e){      				question2.this.windowclosed();      			}      		}      	);      	      	this.addwindowlistener      		(      			new windowadapter(){      				public void windowclosing(windowevent e){      					      				question2.this.windowclosed();      			}      			}      			);      			      			buttonpanel=new question3();      			buttonpanel.setsize(250,400);      			this.add(((question3)buttonpanel).get_panel(),borderlayout.north);      }            protected void windowclosed(){      	system.exit(0);      }            private class resetlistener implements actionlistener      {      	public void actionperformed(actionevent event)      	{      		      		((question3)buttonpanel).reset(new question2());      			setvisible(true);      		      	}      }              }

this 3rd class, named question3

/**   * @(#)question3.java   *   *   * @author    * @version 1.00 2015/5/22   */  import java.awt.*;  import java.awt.event.*;  import javax.swing.*;    public class question3 extends jpanel {  	  	private jpanel primary;  	private jradiobutton button1;  	private jradiobutton button2;  	private jradiobutton button3;  	private jradiobutton button4;  	private jlabel question1;  	private jlabel question2;  	private jlabel question3;  	private jlabel question4;  	private jlabel question5;  	private jlabel question6;  	private jlabel question7;  	private jlabel question8;  	private jlabel question9;  	private jlabel question10;  	private jradiobutton [][] array1;  	private jlabel [][] arrayq;        public question3() {      	/*      	array1 = new jradiobutton[10][4];      	array1[1][0]=new jradiobutton ("a. mesopotamian civilization");      	array1[1][1]=new jradiobutton ("b. egyptian civilization");      	array1[1][2]=new jradiobutton ("c. harrapan civilization");      	array1[1][3]=new jradiobutton ("d. chinese civilization");      	      	array1[2][0]=new jradiobutton ("a. mesopotamian civilization");      	array1[2][1]=new jradiobutton ("b. egyptian civilization");      	array1[2][2]=new jradiobutton ("c. harappan civilization");      	array1[2][3]=new jradiobutton ("d. chinese civilization");      	      	array1[3][0]=new jradiobutton ("a. china");      	array1[3][1]=new jradiobutton ("b. india");      	array1[3][2]=new jradiobutton ("c. irag");      	array1[3][3]=new jradiobutton ("d. egypt");      	      	array1[4][0]=new jradiobutton ("a. aeschylus");      	array1[4][1]=new jradiobutton ("b. sophocles");      	array1[4][2]=new jradiobutton ("c. aristophanes");      	array1[4][3]=new jradiobutton ("d. philip");      	      	array1[5][0]=new jradiobutton ("a. 776 bc");      	array1[5][1]=new jradiobutton ("b. 780 bc");      	array1[5][2]=new jradiobutton ("c. 790 bc");      	array1[5][3]=new jradiobutton ("d. 800 bc");      	      	array1[6][0]=new jradiobutton ("a. euclid");      	array1[6][1]=new jradiobutton ("b. pythagoras");      	array1[6][2]=new jradiobutton ("c. hippocrates");      	array1[6][3]=new jradiobutton ("d. erastosthenes");      	      	array1[7][0]=new jradiobutton ("a. 1000 bc");      	array1[7][1]=new jradiobutton ("b. 1200 bc");      	array1[7][2]=new jradiobutton ("c. 1400 bc");      	array1[7][3]=new jradiobutton ("d. 1600 bc");      	      	array1[8][0]=new jradiobutton ("a. cicero");      	array1[8][1]=new jradiobutton ("b. seneca");      	array1[8][2]=new jradiobutton ("c. lucretius");      	array1[8][3]=new jradiobutton ("d. octavian");      	      	array1[9][0]=new jradiobutton ("a. tacitus");      	array1[9][1]=new jradiobutton ("b. plinky");      	array1[9][2]=new jradiobutton ("c. virgil");      	array1[9][3]=new jradiobutton ("d. marcus");      	      	array1[10][0]=new jradiobutton ("a. 1285-90");      	array1[10][1]=new jradiobutton ("b. 1288-93");      	array1[10][2]=new jradiobutton ("c. 1290-96");      	array1[10][3]=new jradiobutton ("d. 1295-1301");      	*/      	//arrayq declaring      	/*      	arrayq = new jlabel[10][1];      	arrayq[1][0]=new jlabel ("1. rivers tigris , euphrates associated with?");      	arrayq[2][0]=new jlabel ("2. considered oldest civilization of world?");      	arrayq[3][0]=new jlabel ("3. among following called \"gift of nile\"?");      	arrayq[4][0]=new jlabel ("4. considered master of greek comedy?");      	arrayq[5][0]=new jlabel ("5. when ancient olympic games first held?");      	arrayq[6][0]=new jlabel ("6. known father of modern medicine?");      	arrayq[7][0]=new jlabel ("7. rome founded around?");      	arrayq[8][0]=new jlabel ("8. not roman philosopher?");      	arrayq[9][0]=new jlabel ("9. among famous roman poets?");      	arrayq[10][0]=new jlabel ("10. marco polo, venetian traveller, travelled venice china , japan in:");      	*/      	//question declaring      	primary=new jpanel();      	primary.setpreferredsize(new dimension(100,400));      	//font assigning      	question1.setfont(new font("helvetica", font.bold, 24));      	question2.setfont(new font("helvetica", font.bold, 24));      	question3.setfont(new font("helvetica", font.bold, 24));      	question4.setfont(new font("helvetica", font.bold, 24));      	question5.setfont(new font("helvetica", font.bold, 24));      	question6.setfont(new font("helvetica", font.bold, 24));      	question7.setfont(new font("helvetica", font.bold, 24));      	question8.setfont(new font("helvetica", font.bold, 24));      	question9.setfont(new font("helvetica", font.bold, 24));      	question10.setfont(new font("helvetica", font.bold, 24));      	//button assigning      	      	button1=new jradiobutton("a. mesopotamian civilization",false);      	button2=new jradiobutton("b. egyptian civilization",false);      	button3=new jradiobutton("c. harrapan civilization",false);      	button4=new jradiobutton("d. chinese civilization",false);      	      	button1=new jradiobutton("a. mesopotamian civilization",false);      	button2=new jradiobutton("b. egyptian civilization",false);      	button3=new jradiobutton("c. harappan civilization",false);      	button4=new jradiobutton("d. chinese civilization",false);      	      	button1=new jradiobutton("a. china",false);      	button2=new jradiobutton("b. india",false);      	button3=new jradiobutton("c. irag",false);      	button4=new jradiobutton("d. egypt",false);      	      	button1=new jradiobutton("a. aeschylus",false);      	button2=new jradiobutton("b. sophocles",false);      	button3=new jradiobutton("c. aristophanes",false);      	button4=new jradiobutton("d. philip",false);      	      	button1=new jradiobutton("a. 776 bc",false);      	button2=new jradiobutton("b. 780 bc",false);      	button3=new jradiobutton("c. 790 bc",false);      	button4=new jradiobutton("d. 800 bc",false);      	      	button1=new jradiobutton("a. euclid",false);      	button2=new jradiobutton("b. pythagoras",false);      	button3=new jradiobutton("c. hippocrates",false);      	button4=new jradiobutton("d. erastosthenes",false);      	      	button1=new jradiobutton("a. 1000 bc",false);      	button2=new jradiobutton("b. 1200 bc",false);      	button3=new jradiobutton("c. 1400 bc",false);      	button4=new jradiobutton("d. 1600 bc",false);      	      	button1=new jradiobutton("a. cicero",false);      	button2=new jradiobutton("b. seneca",false);      	button3=new jradiobutton("c. lucretius",false);      	button4=new jradiobutton("d. octavian",false);      	      	button1=new jradiobutton("a. tacitus",false);      	button2=new jradiobutton("b. plinky",false);      	button3=new jradiobutton("c. virgil",false);      	button4=new jradiobutton("d. marcus",false);      	      	button1=new jradiobutton("a. 1285-90",false);      	button2=new jradiobutton("b. 1288-93",false);      	button3=new jradiobutton("c. 1290-96",false);      	button4=new jradiobutton("d. 1295-1301",false);      	//array assigning      	question1=new jlabel("1. rivers tigris , euphrates associated with?");      	question2=new jlabel("2. considered oldest civilization of world?");      	question3=new jlabel("3. among following called \"gift of nile\"?");      	question4=new jlabel("4. considered master of greek comedy?");      	question5=new jlabel("5. when ancient olympic games first held?");      	question6=new jlabel("6. known father of modern medicine?");      	question7=new jlabel("7. rome founded around?");      	question8=new jlabel("8. not roman philosopher?");      	question9=new jlabel("9. among famous roman poets?");      	question10=new jlabel("10. marco polo, venetian traveller, travelled venice china , japan in:");      	button1.setbackground(color.magenta);      	button1.setbackground(color.blue);      	button1.setforeground(color.white);      	button1.setforeground(color.yellow);      	primary.setbackground(color.cyan);      	primary.add(question1);      	primary.add(question2);      	primary.add(question3);      	primary.add(question4);      	primary.add(question5);      	primary.add(question6);      	primary.add(question7);      	primary.add(question8);      	primary.add(question9);      	primary.add(question10);      	//primary.add(button1);      	//primary.add(button2);      	//primary.add(button3);      	//primary.add(button4);      	      	questionlistener1 listener1 = new questionlistener1();      	button1.addactionlistener(listener1);      	button2.addactionlistener(listener1);      }      public jpanel get_panel(){      	return primary;      }      public void reset(jframe frame){      	question1.settext("which move better?");      	button1.setselected(false);      	button2.setselected(false);      	      	frame.setvisible(true);      }      public void array1(){      }            private class questionlistener1  implements actionlistener       	{      	public void actionperformed(actionevent event){      		      		if(event.getsource()==button1){      			question1.settext("i love vanilla too");      		}      		if(event.getsource()==button2){      			question1.settext("don't chocolate on shirt");      		}      	}      }              }

your //font assigning section needs come after //array assigning section in question3.java. move block of code down after line starting question10=new jlabel("10. m , should run.

until //array assigning assigns variables each of question# variables they're null, trying call question1.setfont(...) before assigning jlabel question1 throws nullpointerexception saw.