creating a simple calculator

[hobo]

Hi i'm trying to create a calculator. One of the methods is called getOperand.
For this method it takes a string as a parameter (the prompt for the user) and returns that double.
Can anyone explain how I can do this method?

thanks

[JosAH]

Hi i'm trying to create a calculator. One of the methods is called getOperand.
For this method it takes a string as a parameter (the prompt for the user) and returns that double.
Can anyone explain how I can do this method?

Primitives don't have methods; their wrapper classes counterparts take care of that; so, if you want to do something that delivers a double or does something with a double, have a look at the API documentation of the Double class (note the lower case and upper case 'd').

kind regards,

Jos

[Arnold]

While you can make your own methods for converting strings into doubles, it is a lot of work.
You can also use this: Double.parseDouble(myString);
And there comes your double. However be prepared to deal with NumberFormatException.

[raqman]

import java.awt.*; 
import java.lang.*; 
import java.awt.event.*; 
import java.applet.Applet; 
import java.awt.datatransfer.*; 

public class calculator extends Applet 
{ 
 public void init() 
 { 
  calf calWindow = new calf("Java Calculator"); 
  calWindow.setSize(200, 250); 
  calWindow.setVisible(true); 
  calWindow.setResizable(false); 
 } 
}

class calf extends Frame implements WindowListener, ActionListener, KeyListener 
{ 
  String command, copy, arg, chg, txt; 
  double result; 
  String number = "123456789.0"; 
  String operator = "/*-+="; 
  CopyPaste cp; 

  Menu Menu1; 
  MenuBar Menubar1; 
  MenuItem menuitem1, menuitem2, menuitem3; 
  TextField entrytext; 
  Button numbut []; //Number buttons 
  Button combut []; //Command buttons 
  Panel companel, numpanel; 

  public static void main(String[] arguments) 
  { 
   calf calWindow = new calf("Java Calculator"); 
   calWindow.setSize(200, 250); 
   calWindow.setVisible(true); 
  } 

  public calf(String title) 
  { 
   super(title); 
   addWindowListener(this); 
   addKeyListener(this); 

   cp = new CopyPaste(); 
   //cp.clip = getToolkit().getSystemClipboard(); 

   setBackground(Color.blue); 
   setLayout(new GridLayout(1, 1)); 
   Menubar1 = new MenuBar(); 
   Menu1 = new Menu("Edit"); 
   menuitem1 = new MenuItem("&Copy"); 
   Menu1.add(menuitem1); 
   menuitem1.addActionListener(this); 
   menuitem2 = new MenuItem("&Paste"); 
   Menu1.add(menuitem2); 
   menuitem2.addActionListener(this); 
   menuitem3 = new MenuItem("&Exit"); 
   Menu1.add(menuitem3); 
   menuitem3.addActionListener(this); 
   Menubar1.add(Menu1); 
   setMenuBar(Menubar1); 
   GridBagLayout gridbag = new GridBagLayout(); 
   GridBagConstraints constraints = new GridBagConstraints(); 
   setLayout(gridbag); 
   constraints.weighty = 1; 
   constraints.weightx = 1; 
   //constraints.fill = GridBagConstraints.BOTH; 
   Font bigFont = new Font("Courier",Font.BOLD, 14); 
   entrytext = new TextField(20); 
   constraints.gridwidth = GridBagConstraints.REMAINDER; 
   gridbag.setConstraints(entrytext,constraints); 
   add(entrytext); 
   entrytext.setFont(bigFont); 
   entrytext.setEditable(false); 
   entrytext.setForeground(Color.black); 
   entrytext.setBackground(Color.white); 
   entrytext.addKeyListener(this); 
   entrytext.requestFocus(); 

   constraints.weighty = 1; 
   constraints.weightx = 1; 
   companel = new Panel(); 

   constraints.gridwidth = GridBagConstraints.REMAINDER; 
   gridbag.setConstraints(companel,constraints); 
   /* 
    Command GridLayout 
    --------------------- 
    | Back |  CE  |  C | 
    --------------------- 
   */ 

   companel.setLayout(new GridLayout(1,3,5,5)); 

   // Create the buttons 
   Font comsFont = new Font("Arial",Font.BOLD, 12); 
   String[] coms = { "Back","CE","C" 
             }; 
   combut = new Button[3]; 
         for (int i=0; i<=2; i++) 
      { 
       combut[i] = new Button(coms[i]); 
       companel.add(combut[i]); 
    combut[i].addActionListener(this); 
    combut[i].setFont(comsFont); 
    combut[i].addKeyListener(this); 

   } 
   add(companel); 
   companel.addKeyListener(this); 

   constraints.weighty = 4; 
   constraints.weightx = 1; 
   numpanel = new Panel(); 
   constraints.gridwidth = GridBagConstraints.REMAINDER; 
   gridbag.setConstraints(numpanel,constraints); 
   /* 
    Number GridLayout 
    --------------------- 
    | 7 | 8 | 9 | / |sqr| 
    --------------------- 
    | 4 | 5 | 6 | * | % | 
    --------------------- 
    | 1 | 2 | 3 | - |1/x| 
    --------------------- 
    | 0 |+/-| . | + | = | 
    --------------------- 
            */ 
   numpanel.setLayout(new GridLayout(4,5,3,3)); 
   // Create the buttons 
   String[] nums = { "7","8","9","/","sqrt", 
              "4","5","6","*","%", 
              "1","2","3","-","1/x", 
              "0","+/-",".","+","=" 
             }; 
   numbut = new Button[20]; 
   for (int i=0; i<=19; i++) 
       { 
       numbut[i] = new Button(nums[i]); 
       numpanel.add(numbut[i]); 
    numbut[i].addActionListener(this); 
    numbut[i].addKeyListener(this); 
    if(operator.indexOf(nums[i]) > -1) 
    { 
     numbut[i].setForeground(Color.red); 
    } 
    else 
    { 
     numbut[i].setForeground(Color.blue); 
    } 

   } 
   add(numpanel); 
   numpanel.addKeyListener(this); 

   //initialize global variables. 
   command = "+"; 
   copy = ""; 
   chg = "N"; 
   txt = ""; 
   arg = ""; 
   result = 0; 
  } 

  public void actionPerformed(ActionEvent e) 
  { 
   if (e.getActionCommand() == "&Exit") 
   { 
    setVisible(false); 
    System.exit(0); 
   } 
   else if (e.getActionCommand() == "&Copy") 
         { 
    String txt = entrytext.getText(); 
    if (txt != null) 
          { 
              cp.doCopy(txt); 
          } 
   } 
   else if (e.getActionCommand() == "&Paste") 
         { 
          cp.doPaste(); 
    if (cp.ctxt != null) 
          { 
     entrytext.setText(cp.ctxt); 
    } 
   } 
   else if (e.getActionCommand() == "Back") back_space(); 
   else if (e.getActionCommand() == "CE") entrytext.setText(""); 
   else if (e.getActionCommand() == "C") 
   { 
    result = 0; 
    command = "+"; 
    entrytext.setText(""); 
   } 
   else 
   { 
    arg = e.getActionCommand(); 
    txt = entrytext.getText(); 
    if(number.indexOf(arg) > -1) 
    { 
     if (chg == "Y") txt = ""; 
     txt = txt + arg; 
     entrytext.setText(txt); 
     chg = "N"; 
    } 
    else check_entry(); 
   } 
  } 

  public void keyPressed(KeyEvent k){} 
  public void keyReleased(KeyEvent k) 
  { 
   int ikey = k.getKeyCode(); 
   if (ikey == 127) entrytext.setText(""); 
  } 
  public void keyTyped(KeyEvent k) 
  { 
   int ikey = k.getKeyChar(); 
   if (ikey == 8) back_space(); 
   else if (ikey == 10) 
   { 
    arg = "="; 
    txt = entrytext.getText(); 
    display_ans(); 
   } 
   else 
   { 
    txt = entrytext.getText(); 
    char ckey = (char) ikey; 
    arg = String.valueOf(ckey); 
    if(number.indexOf(arg) > -1) 
    { 
     if (chg == "Y") txt = ""; 
     txt = txt + arg; 
     entrytext.setText(txt); 
     chg = "N"; 
    } 
    else check_entry(); 
   } 
  } 

  public void back_space() 
  { 
   txt = entrytext.getText(); 
   int l = txt.length(); 
   if (l > 0) 
   { 
    txt = txt.substring(0,l-1); 
    entrytext.setText(txt); 
   } 
  } 
  public void display_ans() 
  { 
   entrytext.setText(compute_tot(txt,command)); 
   chg = "Y"; 
   command = "+"; 
   result = 0; 
  } 
  public void check_entry() 
  { 
   if(arg.equals("=")) display_ans(); 
   else if(arg.equals("%")) 
   { 
    entrytext.setText(compute_tot(txt,arg)); 
    chg = "Y"; 
   } 
   else if(operator.indexOf(arg) > -1) 
   { 
    entrytext.setText(compute_tot(txt,command)); 
    command = arg; 
    chg = "Y"; 
   } 
   else if(arg == "sqrt") 
   { 
    entrytext.setText(compute_tot(txt,arg)); 
    chg = "Y"; 
    command = ""; 
   } 
   else if(arg == "+/-") 
   { 
    Double tnum = Double.valueOf(txt); 
    double num = tnum.doubleValue(); 
    num = num * -1; 
    entrytext.setText(String.valueOf(num)); 
    chg = "Y"; 
   } 
   else if(arg == "1/x") 
   { 
    entrytext.setText(compute_tot(txt,arg)); 
    chg = "Y"; 
   } 
  } 
  String compute_tot(String t, String c) 
  { 
   Double tnum = Double.valueOf(t); 
   double num = tnum.doubleValue(); 

   if (c.equals("+")) result = result + num; 
   else if (c.equals("-")) result = result - num; 
   else if (c.equals("*")) result = result * num; 
   else if (c.equals("/")) result = result / num; 
   else if (c.equals("%")) result = num / 100; 
   else if (c.equals("+/-")) result = num * -1; 
   else if (c.equals("1/x")) result = 1.000 / num; 
   else if (c.equals("sqrt")) result = Math.sqrt(num); 
   return String.valueOf(result); 
  } 

  public void windowClosing(WindowEvent we) 
  { 
   setVisible(false); 
   System.exit(0); 
  } 
  public void windowClosed(WindowEvent we) {} 
  public void windowDeiconified(WindowEvent we) {} 
  public void windowIconified(WindowEvent we) {} 
  public void windowOpened(WindowEvent we) {} 
  public void windowActivated(WindowEvent we) {} 
  public void windowDeactivated(WindowEvent we) {} 
} 
  

class CopyPaste implements ClipboardOwner 
{ 

    Clipboard clip; 
    String ctxt; 

    CopyPaste() 
    { 
  clip = new Clipboard("clip"); 
        ctxt = null; 
    } 

    void doCopy(String txt) 
    { 
        StringSelection trans = new StringSelection(txt); 
        clip.setContents(trans, this); 
    } 

    void doPaste() 
    { 
  ctxt = null; 
        Transferable toPaste = clip.getContents(this); 
        if (toPaste != null) 
        { 
            try 
            { 
                ctxt = (String)toPaste.getTransferData( 
                    DataFlavor.stringFlavor); 
            } 
            catch (Exception e) 
            { 
             System.out.println("Error -- " + e.toString()); 
   } 
        } 

    } 

    public void lostOwnership(Clipboard clip, 
        Transferable contents) { 
    } 
}

[Eranga]

Please use code tags next time when you post code segment here in the forum. Unformated codes are hard to read.