Simple GUI Java calculator

Question

I am building a simple GUI Java calculator. I have an issue finding a package or figuring out a method to do the actual calculation. So far I've figured that when I do a math operation, the number in the text box gets saved in a temporary location.

Then when I click on the "=" button, it will do the calculation, but I don't know how to tell it to take the temporary plus the math operation and the second number and do the calculation based on the selected math operation clicked, +, -, *, /

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;

public class JavaCalculator extends JFrame {
    private JButton jbtNum1;
        private JButton jbtNum2;
        private JButton jbtNum3;
        private JButton jbtNum4;
        private JButton jbtNum5;
        private JButton jbtNum6;
        private JButton jbtNum7;
        private JButton jbtNum8;
        private JButton jbtNum9;
        private JButton jbtNum0;
    private JButton jbtEqual;
        private JButton jbtAdd;
        private JButton jbtSubtract;
        private JButton jbtMultiply;
        private JButton jbtDivide;
        private JButton jbtSolve;
        private JButton jbtClear;
        private double TEMP;
        private double SolveTEMP;
    private JTextField jtfResult;
    String display = "";

    public JavaCalculator() {
        JPanel p1 = new JPanel();
        p1.setLayout(new GridLayout(4, 3));
        p1.add(jbtNum1 = new JButton("1"));
        p1.add(jbtNum2 = new JButton("2"));
        p1.add(jbtNum3 = new JButton("3"));
        p1.add(jbtNum4 = new JButton("4"));
        p1.add(jbtNum5 = new JButton("5"));
        p1.add(jbtNum6 = new JButton("6"));
        p1.add(jbtNum7 = new JButton("7"));
        p1.add(jbtNum8 = new JButton("8"));
        p1.add(jbtNum9 = new JButton("9"));
        p1.add(jbtNum0 = new JButton("0"));
        p1.add(jbtClear = new JButton("C"));


        JPanel p2 = new JPanel();
        p2.setLayout(new FlowLayout());
        p2.add(jtfResult = new JTextField(20));
        jtfResult.setHorizontalAlignment(JTextField.RIGHT);
        jtfResult.setEditable(false);

                JPanel p3 = new JPanel();
                p3.setLayout(new GridLayout(5, 1));
                p3.add(jbtAdd = new JButton("+"));
                p3.add(jbtSubtract = new JButton("-"));
                p3.add(jbtMultiply = new JButton("*"));
                p3.add(jbtDivide = new JButton("/"));
                p3.add(jbtSolve = new JButton("="));

        JPanel p = new JPanel();
        p.setLayout(new GridLayout());
        p.add(p2, BorderLayout.NORTH);
        p.add(p1, BorderLayout.SOUTH);
        p.add(p3, BorderLayout.EAST);


        add(p);

        jbtNum1.addActionListener(new ListenToOne());
        jbtNum2.addActionListener(new ListenToTwo());
        jbtNum3.addActionListener(new ListenToThree());
                jbtNum4.addActionListener(new ListenToFour());
        jbtNum5.addActionListener(new ListenToFive());
        jbtNum6.addActionListener(new ListenToSix());
        jbtNum7.addActionListener(new ListenToSeven());
        jbtNum8.addActionListener(new ListenToEight());
        jbtNum9.addActionListener(new ListenToNine());
        jbtNum0.addActionListener(new ListenToZero());

        jbtAdd.addActionListener(new ListenToAdd());
        jbtSubtract.addActionListener(new ListenToSubtract());
        jbtMultiply.addActionListener(new ListenToMultiply());
        jbtDivide.addActionListener(new ListenToDivide());
        jbtSolve.addActionListener(new ListenToSolve());



    } //JavaCaluclator()

    class ListenToOne implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            display = jtfResult.getText();
            jtfResult.setText(display + "1");
        }
    }
    class ListenToTwo implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            display = jtfResult.getText();
            jtfResult.setText(display + "2");
        }
    }
    class ListenToThree implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            display = jtfResult.getText();
            jtfResult.setText(display + "3");
        }
    }
    class ListenToFour implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            display = jtfResult.getText();
            jtfResult.setText(display + "4");
        }
    }
    class ListenToFive implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            display = jtfResult.getText();
            jtfResult.setText(display + "5");
        }
    }
    class ListenToSix implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            display = jtfResult.getText();
            jtfResult.setText(display + "6");
        }
    }
    class ListenToSeven implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            display = jtfResult.getText();
            jtfResult.setText(display + "7");
        }
    }
    class ListenToEight implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            display = jtfResult.getText();
            jtfResult.setText(display + "8");
        }
    }
    class ListenToNine implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            display = jtfResult.getText();
            jtfResult.setText(display + "9");
        }
    }
    class ListenToZero implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            display = jtfResult.getText();
            jtfResult.setText(display + "0");
        }
    }

        class ListenToAdd implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            TEMP = Double.parseDouble(jtfResult.getText());
                        jtfResult.setText("");

        }
    }
    class ListenToSubtract implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            display = jtfResult.getText();
            jtfResult.setText(display + "0");
        }
    }
    class ListenToMultiply implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            display = jtfResult.getText();
            jtfResult.setText(display + "0");
        }
    }
    class ListenToDivide implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            display = jtfResult.getText();
            jtfResult.setText(display + "0");
        }
    }
    class ListenToSolve implements ActionListener {
        public void actionPerformed(ActionEvent e) {
                        SolveTEMP = jtfResult.getText();
            jtfResult.setText(TEMP + Double.parseDouble(jtfResult);
        }
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        JavaCalculator calc = new JavaCalculator();
        calc.pack();
        calc.setLocationRelativeTo(null);
                calc.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        calc.setVisible(true);
    }

} //JavaCalculator

User · Answer

assuming that string1 is your whole operation

use mdas

double result;
string recurAndCheck(string operation){
  if(operation.indexOf("/")){
     String leftSide = recurAndCheck(operation.split("/")[0]);
     string rightSide = recurAndCheck(operation.split("/")[1]);
     result = Double.parseDouble(leftSide)/Double.parseDouble(rightSide);

  } else if (..continue w/ *...) {
    //same as above but change / with *
  } else if (..continue w/ -) { 
    //change as above but change with -
  } else if (..continuew with +) {
    //change with add
  } else {
    return;
  }
}

User · Answer

What you need is something that calculates the result of the infix notated calculation, have a look at the Shunting-Yard Algorithm.

There's an example in C++ on Wikipedia's page, but it shouldn't be too hard to implement it in Java.
And since it's the primary function of your calculator, I would advise you to not grab some codez from the Web in this Case (except all you want to do is building calculator GUIs).

User · Answer

This is the working code     import java awt    import java awt event    import javax swing    import java util     public class JavaCalculator extends JFrame        private JButton jbtNum1      private JButton jbtNum2      private JButton jbtNum3      private JButton jbtNum4      private JButton jbtNum5      private JButton jbtNum6      private JButton jbtNum7      private JButton jbtNum8      private JButton jbtNum9      private JButton jbtNum0      private JButton jbtEqual      private JButton jbtAdd      private JButton jbtSubtract      private JButton jbtMultiply      private JButton jbtDivide      private JButton jbtSolve      private JButton jbtClear      private double TEMP      private double SolveTEMP      private JTextField jtfResult       Boolean addBool   false      Boolean subBool   false      Boolean divBool   false      Boolean mulBool   false       String display            public JavaCalculator              JPanel p1   new JPanel            p1 setLayout new GridLayout 4  3            p1 add jbtNum1   new JButton  1             p1 add jbtNum2   new JButton  2             p1 add jbtNum3   new JButton  3             p1 add jbtNum4   new JButton  4             p1 add jbtNum5   new JButton  5             p1 add jbtNum6   new JButton  6             p1 add jbtNum7   new JButton  7             p1 add jbtNum8   new JButton  8             p1 add jbtNum9   new JButton  9             p1 add jbtNum0   new JButton  0             p1 add jbtClear   new JButton  C              JPanel p2   new JPanel            p2 setLayout new FlowLayout             p2 add jtfResult   new JTextField 20            jtfResult setHorizontalAlignment JTextField RIGHT           jtfResult setEditable false            JPanel p3   new JPanel            p3 setLayout new GridLayout 5  1            p3 add jbtAdd   new JButton                p3 add jbtSubtract   new JButton  -             p3 add jbtMultiply   new JButton                p3 add jbtDivide   new JButton                p3 add jbtSolve   new JButton                 JPanel p   new JPanel            p setLayout new GridLayout             p add p2  BorderLayout NORTH           p add p1  BorderLayout SOUTH           p add p3  BorderLayout EAST            add p            jbtNum1 addActionListener new ListenToOne             jbtNum2 addActionListener new ListenToTwo             jbtNum3 addActionListener new ListenToThree             jbtNum4 addActionListener new ListenToFour             jbtNum5 addActionListener new ListenToFive             jbtNum6 addActionListener new ListenToSix             jbtNum7 addActionListener new ListenToSeven             jbtNum8 addActionListener new ListenToEight             jbtNum9 addActionListener new ListenToNine             jbtNum0 addActionListener new ListenToZero              jbtAdd addActionListener new ListenToAdd             jbtSubtract addActionListener new ListenToSubtract             jbtMultiply addActionListener new ListenToMultiply             jbtDivide addActionListener new ListenToDivide             jbtSolve addActionListener new ListenToSolve             jbtClear addActionListener new ListenToClear             JavaCaluclator        class ListenToClear implements ActionListener           public void actionPerformed ActionEvent e                  display   jtfResult getText                jtfResult setText                  addBool   false              subBool   false              mulBool   false              divBool   false               TEMP   0              SolveTEMP   0                       class ListenToOne implements ActionListener           public void actionPerformed ActionEvent e                display   jtfResult getText                jtfResult setText display    1                         class ListenToTwo implements ActionListener           public void actionPerformed ActionEvent e                display   jtfResult getText                jtfResult setText display    2                         class ListenToThree implements ActionListener           public void actionPerformed ActionEvent e                display   jtfResult getText                jtfResult setText display    3                         class ListenToFour implements ActionListener           public void actionPerformed ActionEvent e                display   jtfResult getText                jtfResult setText display    4                         class ListenToFive implements ActionListener           public void actionPerformed ActionEvent e                display   jtfResult getText                jtfResult setText display    5                         class ListenToSix implements ActionListener           public void actionPerformed ActionEvent e                display   jtfResult getText                jtfResult setText display    6                         class ListenToSeven implements ActionListener           public void actionPerformed ActionEvent e                display   jtfResult getText                jtfResult setText display    7                         class ListenToEight implements ActionListener           public void actionPerformed ActionEvent e                display   jtfResult getText                jtfResult setText display    8                         class ListenToNine implements ActionListener           public void actionPerformed ActionEvent e                display   jtfResult getText                jtfResult setText display    9                         class ListenToZero implements ActionListener           public void actionPerformed ActionEvent e                display   jtfResult getText                jtfResult setText display    0                         class ListenToAdd implements ActionListener           public void actionPerformed ActionEvent e                TEMP   Double parseDouble jtfResult getText                 jtfResult setText                  addBool   true                       class ListenToSubtract implements ActionListener           public void actionPerformed ActionEvent e                TEMP   Double parseDouble jtfResult getText                 jtfResult setText                  subBool   true                       class ListenToMultiply implements ActionListener           public void actionPerformed ActionEvent e                TEMP   Double parseDouble jtfResult getText                 jtfResult setText                  mulBool   true                       class ListenToDivide implements ActionListener           public void actionPerformed ActionEvent e                TEMP   Double parseDouble jtfResult getText                 jtfResult setText                  divBool   true                       class ListenToSolve implements ActionListener           public void actionPerformed ActionEvent e                SolveTEMP   Double parseDouble jtfResult getText                 if  addBool    true                  SolveTEMP   SolveTEMP   TEMP              else if   subBool    true                  SolveTEMP   SolveTEMP - TEMP              else if   mulBool    true                  SolveTEMP   SolveTEMP   TEMP              else if   divBool    true                              SolveTEMP   SolveTEMP   TEMP              jtfResult setText   Double toString SolveTEMP                 addBool   false              subBool   false              mulBool   false              divBool   false                       public static void main String   args               TODO Auto-generated method stub         JavaCalculator calc   new JavaCalculator            calc pack            calc setLocationRelativeTo null                   calc setDefaultCloseOperation JFrame EXIT ON CLOSE           calc setVisible true              JavaCalculator

User · Answer

Somewhere you have to keep track of what button had been pressed. When things happen, you need to store something in a variable so you can recall the information or it's gone forever.

When someone pressed one of the operator buttons, don't just let them type in another value. Save the operator symbol, then let them type in another value. You could literally just have a String operator that gets the text of the operator button pressed. Then, when the equals button is pressed, you have to check to see which operator you stored. You could do this with an if/else if/else chain.

So, in your symbol's button press event, store the symbol text in a variable, then, in the = button press event, check to see which symbol is in the variable and act accordingly.

Alternatively, if you feel comfortable enough with enums (looks like you're just starting, so if you're not to that point yet, ignore this), you could have an enumeration of symbols that lets you check symbols easily with a switch.

[java] Simple GUI Java calculator

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