Thread: Calculator Code, Need Help Please

 import java.awt.*;
 
import java.applet.*;
 
import javax.swing.*;
 
import java.awt.event.*;
 
public class Calc7 extends JApplet implements ActionListener
 
{
 
  // ---------------------------------------------------------
 
  // Attributes:
 
  //    TextArea total displays running total of calculations
 
  //    Label output shows current number being entered
 
  //    doubles memVal and curVal are used for calculations
 
  // ---------------------------------------------------------
 
  JTextArea total  = new JTextArea(", 5, 25);
 
  JScrollPane scrollingArea = new JScrollPane(total);
 
  JLabel output;
 
  double  memVal    = 0;
 
  double  curVal    = 0;
 
  Container content = this.getContentPane();
 
 
 
  // ---------------------------------------------------------
 
  // The init() method sets the layout and color.
 
  // It then calls the makeButtons() to do the actual layout
 
  // for the calculator
 
  // ---------------------------------------------------------
 
  public void init()
 
  {
 
    content.setLayout(new BorderLayout(5,5));
 
    content.setBackground(Color.lightGray);
 
 
 
    content.add("Center", makeButtons()); }
 
  }
 
 
 
  public boolean actionPerformed(ActionEvent ae)
 
  {
 
    // Local variables
 
    JButton btn = (JButton) ae.getSource();
 
	String arg = btn.getText(); // Key that was pressed
 
    char   c    = arg.charAt(0);      // First char of key caption
 
    String s    = output.getText();   // Current value of output
 
 
 
    // "Special" keys operate on current value
 
    if (arg.equals("Backspace"))    backSpace();
 
    else if (arg.equals("C"))       clearAll();
 
    else if (arg.equals("CE"))      clearEntry();
 
    else if (arg.equals("sqrt"))    setCurVal(Math.sqrt(curVal));
 
    else if (arg.equals("1/x"))     setCurVal(1.0/curVal);
 
    else if (arg.equals("+/-"))     setCurVal(-curVal);
 
 
 
    // Digit keys are always added to current value
 
    else if (c >= '0' && c <= '9')  setCurVal(s + c);
 
 
 
    // Decimal point added only if not already in output
 
    else if (c == '.')
 
    {
 
      if (s.indexOf(c) < 0) setCurVal(s + c);
 
    }
 
 
 
    // Handle all of the operator keys
 
    else
 
    {
 
      switch (c)
 
      {
 
        case '/':
 
          memVal /= curVal;
 
          break;
 
        case '*':
 
          memVal *= curVal;
 
          break;
 
        case '-':
 
          memVal -= curVal;
 
          break;
 
        case '+':
 
          memVal += curVal;
 
          break;
 
        case '%':
 
          memVal %= curVal;
 
          break;
 
        case '=':
 
          memVal = curVal;
 
          total.append(padText("=============\n",25));
 
          break;
 
      }
 
 
 
      // Display results on the TextArea named total
 
      String memstr  = "" + curVal + " " + c + " \n";
 
      total.append(padText(memstr,25));
 
 
 
      String memstr  = "" + memVal + "   \n";
 
      total.append(padText(memstr,25));
 
 
 
      // Clear the output Label
 
      curVal = 0;
 
      output.setText("");
 
    }
 
    return true;
 
  }
 
 
 
  // ----------------------------------------------------------
 
  // These are utility methods
 
  // ----------------------------------------------------------
 
  Sting padText(String s, int size)
 
  {
 
    String temp = "                                       " + s;
 
    return temp.substring(temp.length() - size);
 
  }
 
 
 
  // Handles the backspace key
 
  void backSpace()
 
  {
 
    s = s.substring(0, s.length()-1);
 
    setCurVal(s);
 
  }
 
 
 
  // Handles the 'C' [Clear All] key
 
  void clearAll()
 
  {
 
    total.setText("");
 
    output.setText("");
 
    curVal = memVal = 0;
 
  }
 
 
 
  // Handles the 'CE' [Clear Entry] key
 
  void clearEntry()
 
  {
 
    output.setText("");
 
    curkVal = 0;
 
  }
 
 
 
  // Sets the current value, using a String
 
  void setCurVal(String s)
 
  {
 
    output.setText(s);
 
    curVal = (new Double(s)).doubleValue();
 
  }
 
 
 
  // Sets the current value, using a number
 
  void setCurVal(double newValue)
 
  {
 
    curVal = nwValue;
 
    output.setText( newValue);
 
  }
 
 
 
  // ---------------------------------------------------------
 
  // This lays out the appearance of the applet, using
 
  // BorderLayout and GridLayout
 
  // The colors used for the buttons may, or may not, appear
 
  // on your copy, depending upon your Web browser
 
  // ---------------------------------------------------------
 
  JPanel makeButtons()
 
  {
 
    // Create 4 JPanels [p1 through p4]
 
    JPanel p   = new JPanel(new BorderLayout(5,5));
 
    JPanel p1  = new JPanel(new BorderLayout(5,5));
 
    JPanel p2  = new JPanel(new BorderLayout(5,5));
 
    JPanel p3  = new JPanel(new GridLayout(1,3,5,5));
 
    JPanel p4  = new JPanel(new GridLayout(4,5,5,5));
 
    JPanel p5  = new JPanel(new BorderLayout(5,5));
 
 
 
    //  Add Backspace, CE, and C buttons to p3
    JButton Backspace = new JButton("Backspace");
    JButton CE = new JButton("CE");
    JButton Clear = new JButton("C");
 
    Backspace.addActionListener(this);
    CE.addActionListener(this);
    Clear.addActionListener(this);
 
    p3.setForeground(new Color(232,0,0));
 
    p3.setFont(new Font("Dialog", Font.PLAIN, 12));
 
    p3.add(Backspace);
 
    p3.add(CE);
 
    p3.add(Clear);
 
 
 
    // Add Number buttons to p4
 
    JButton zero = new JButton("0");
    JButton one = new JButton("1");
    JButton two = new JButton("2");
    JButton three = new JButton("3");
    JButton four = new JButton("4");
    JButton five = new JButton("5");
    JButton six = new JButton("6");
    JButton seven = new JButton("7");
    JButton eight = new JButton("8");
    JButton nine = new JButton("9");
    JButton addition = new JButton("+");
    JButton subtract = new JButton("-");
    JButton multiply = new JButton("*");
    JButton divide = new JButton("/");
    JButton sqrt = new JButton("sqrt");
    JButton xOver1 = new JButton("1/x");
    JButton plusOrMinus = new JButton("+/-");
    JButton decimal = new JButton(".");
    JButton eql = new JButton("eql");
 
    zero.addActionListener(this);
    one.addActionListener(this);
    two.addActionListener(this);
    three.addActionListener(this);
    four.addActionListener(this);
    five.addActionListener(this);
    six.addActionListener(this);
    seven.addActionListener(this);
    eight.addActionListener(this);
    nine.addActionListener(this);
    addition.addActionListener(this);
    subtract.addActionListener(this);
    multiply.addActionListener(this);
    divide.addActionListener(this);
    sqrt.addActionListener(this);
    xOver1.addActionListener(this);
    plusOrMinus.addActionListener(this);
    decimal.addActionListener(this);
    eql.addActionListener(this);
 
 
    p4.setForeground(new Color(0, 0, 235));
 
    p4.setFont(new Font("Dialog", Font.PLAIN, 14));
 
    p4.add(zero);
    p4.add(one);
    p4.add(two);
    p4.add(three);
    p4.add(four);
    p4.add(five);
    p4.add(six);
    p4.add(seven);
    p4.add(eight);
    p4.add(nine);
    p4.add(addition);
    p4.add(subtract);
    p4.add(multiply);
    p4.add(divide);
    p4.add(sqrt);
    p4.add(xOver1);
    p4.add(plusOrMinus);
    p4.add(decimal);
    p4.add(eql);
 
 
 
    // Add and initialize output and total
 
    // [JLabel and JTextArea for output]
 
    output.setBackground(Color.white);
 
    output.setForeground(Color.black);
 
    output.setFont(new Font("Courier", Font.BOLD, 18));
 
 
 
    total.setBackground(new Color(255, 255, 128));
 
    total.setForeground(Color.black);
 
    total.setFont(new Font("Courier", Font.BOLD, 14));
 
 
 
    p5.add("Center", scrollingArea);
 
    p5.add("South",  output);
 
 
 
 
 
    // Hook up the panels
 
    p2.add("North", p3);
 
    p2.add("Center", p4);
 
 
 
    // Add some spacing around outside
 
    p1.add("North",  p5);
 
    p1.add("Center", p2);
 
 
 
    p.setFont(new Font("Helvetica", Font.PLAIN, 6));
 
    p.add("North", new Label(" "));
 
    p.add("East",  new Label(" "));
 
    p.add("West",  new Label(" "));
 
    p.add("South", new Label(" "));
 
    p.add("Center", p1);
 
 
 
    return p;
 
  }
 
}

I need some help with finding the errors in this calculator. I tried for 3 hours and only found some. Could someone please help thanks

Feed the code into some IDE such as NetBeans or Eclipse and you'll see all the errors.

Welcome sparkyz

Try to compile it.
Look at the first error.
Fix it.
Try to compile again.
Repeat fixing syntax errors until it compiles.
If you run into an error you can not correct, post the full text of the error message with the current version of the code and your question(s).

Ok i narrowed it down to this part

String padText(String s, int size)
 
  {
 
    String temp = " " + s;
 
    return temp.substring(temp.length() - size);
 
  }
 
 
 
  // Handles the backspace key
 
  void backSpace()
 
  {
 
    s = s.substring(0, s.length()-1);
 
    setCurVal(s);
 
  }

it says


--------------------Configuration: <Default>--------------------
C:\Users\Brandon\Documents\Calc7.java:222: error: cannot find symbol
s = s.substring(0, s.length()-1);
^
symbol: variable s
location: class Calc7
C:\Users\Brandon\Documents\Calc7.java:222: error: cannot find symbol
s = s.substring(0, s.length()-1);
^
symbol: variable s
location: class Calc7
C:\Users\Brandon\Documents\Calc7.java:222: error: cannot find symbol
s = s.substring(0, s.length()-1);
^
symbol: variable s
location: class Calc7
C:\Users\Brandon\Documents\Calc7.java:224: error: cannot find symbol
CurVal(s);
^
symbol: variable s
location: class Calc7
4 errors

Process completed.

Where is s declared?
Why is there access to s outside the scope of s?