java - Attempting to write code for a simple calculator. Trouble getting the program to solve the equation that the user inputs -

currently when user presses buttons on calculator displays value on text box above, cannot solve equation. every button pressed displays in textfield when press '=' (equals) solves equation. me problem please?

//michael moradi //period c1 //june 2, 2015 //final project semester 2  import javax.swing.*; //imports needed code  import java.awt.*; import java.awt.event.*;  public class calculator extends jframe implements actionlistener {      public jbutton button1, button2, button3, button4, button5, button6, button7, button8, button9, button10, button11, button12, button13, button14, button15, button16;     public jtextarea text; //makes these accessible throughout code      public calculator()     {         setsize(350,300); //sets size 300 300         setresizable(false); //does not let user change size of window         setdefaultcloseoperation(exit_on_close);//makes app close when press x on top left          container contentpane = getcontentpane();//gets contentpane         contentpane.setbackground(color.cyan);//sets background color white                   contentpane.setlayout(new flowlayout());//makes contentpane read left right          text = new jtextarea(1, 25);         contentpane.add(text);         text.seteditable(false);          button1 = new jbutton ("7");         contentpane.add(button1);         button1.addactionlistener(this);          button2 = new jbutton ("8");         contentpane.add(button2);         button2.addactionlistener(this);          button3 = new jbutton ("9");         contentpane.add(button3);         button3.addactionlistener(this);          button4 = new jbutton ("÷");         contentpane.add(button4);         button4.addactionlistener(this);          button5 = new jbutton ("4");         contentpane.add(button5);         button5.addactionlistener(this);          button6 = new jbutton ("5");         contentpane.add(button6);         button6.addactionlistener(this);          button7 = new jbutton ("6");         contentpane.add(button7);         button7.addactionlistener(this);          button8 = new jbutton ("x");         contentpane.add(button8);         button8.addactionlistener(this);          button9 = new jbutton ("1");         contentpane.add(button9);         button9.addactionlistener(this);          button10 = new jbutton ("2");         contentpane.add(button10);         button10.addactionlistener(this);          button11 = new jbutton ("3");         contentpane.add(button11);         button11.addactionlistener(this);          button12 = new jbutton ("-");         contentpane.add(button12);         button12.addactionlistener(this);          button13 = new jbutton ("0");         contentpane.add(button13);         button13.addactionlistener(this);          button14 = new jbutton ("c");         contentpane.add(button14);         button14.addactionlistener(this);          button15 = new jbutton ("=");         contentpane.add(button15);         button15.addactionlistener(this);          button16 = new jbutton ("+");         contentpane.add(button16);         button16.addactionlistener(this);        }      public static void main(string[] args)     {         calculator guiwindow = new calculator(); //uses gui         guiwindow.setvisible(true); //makes visible      }      public void actionperformed(actionevent e)     {         container contentpane = getcontentpane();          string enterednumbers = text.gettext();          if (e.getactioncommand().equals("7"))         text.settext(enterednumbers + ("7"));          if (e.getactioncommand().equals("8"))         text.settext(enterednumbers + ("8"));          if (e.getactioncommand().equals("9"))         text.settext(enterednumbers + ("9"));          if (e.getactioncommand().equals("÷"))         text.settext(enterednumbers + ("÷"));          if (e.getactioncommand().equals("4"))         text.settext(enterednumbers + ("4"));          if (e.getactioncommand().equals("5"))         text.settext(enterednumbers + ("5"));          if (e.getactioncommand().equals("6"))         text.settext(enterednumbers + ("6"));          if (e.getactioncommand().equals("x"))         text.settext(enterednumbers + ("x"));          if (e.getactioncommand().equals("1"))         text.settext(enterednumbers + ("1"));          if (e.getactioncommand().equals("2"))         text.settext(enterednumbers + ("2"));          if (e.getactioncommand().equals("3"))         text.settext(enterednumbers + ("3"));          if (e.getactioncommand().equals("-"))         text.settext(enterednumbers + ("-"));          if (e.getactioncommand().equals("0"))         text.settext(enterednumbers + ("0"));          if (e.getactioncommand().equals("c"))         text.settext("");          if (e.getactioncommand().equals("="))         text.settext(enterednumbers + ("="));          if (e.getactioncommand().equals("+"))         text.settext(enterednumbers + ("+"));         }  } 

for this, want change actionlistener. every other button—which encourage give more meaningful names, way—simply adds token of text calculator field. "=" meant, description, solve it. so,

if (e.getactioncommand().equals("="))     text.settext(enterednumbers + ("=")); 

should more this:

if (e.getactioncommand().equals("=")) {     string math = text.gettext();     answerfield.settext(solve(math)); }  private solve(string math) {     //this tricky part, see description next. } 

for solving method, suggest 1 of 2 things. first break down series of regular expressions, can create , try out (before implementing) here. there, know whether provided field number, or operator. operators best paired enumerations , function fields. unfortunately, still leaves question of how handle operator precedence open.

for that, you'll want break down reverse polish notation; shunting-yard algorithm. after that, can step through , apply each operation function in order appears.

if you're in hurry, use java scripting engine , implement math solvable javascript; tutorial available here. currently, javascript/ecmascript available, i'm sure there plenty of others available through external libraries. (when you're dealing changing dynamic code, it's godsend.)

hopefully 1 of these resources you. once implemented script in java focused on solving mathematical equations, using first method; , plug in new applications second method. best of luck!