A very simple calculator

Today, I was asked to write a calculator on the iPhone. After all, I was not very familiar with it. I spent an hour writing a calculator in Java. It was very easy to go through the next process. The Code is as follows:

/* * To change this template, choose Tools | Templates * and open the template in the editor. */package calculator;import java.awt.BorderLayout;import java.awt.GridLayout;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JPanel;/** * * @author GL */public class Calculator extends JFrame{    /**     * @param args the command line arguments     */        int first = 0;    int second = 0;    int select = 0;    int counter = 0;    input in;    JLabel out = new JLabel("0");        public static void main(String[] args) {        // TODO code application logic here        JFrame j = new Calculator();    }        public Calculator(){        in = new input();        setLayout(new BorderLayout());        add(in,BorderLayout.CENTER);        add(out,BorderLayout.NORTH);        this.setVisible(true);        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        this.setTitle("Calculator");           }        class input extends JPanel{        public input(){            setLayout(new GridLayout(5,4));            JButton[] enter = new JButton[20];                        enter[0] = new JButton("c");            enter[1] = new JButton("<-");            enter[2] = new JButton("/");            enter[3] = new JButton("*");            enter[4] = new JButton("7");            enter[5] = new JButton("8");            enter[6] = new JButton("9");            enter[7] = new JButton("-");            enter[8] = new JButton("4");            enter[9] = new JButton("5");            enter[10] = new JButton("6");            enter[11] = new JButton("+");            enter[12] = new JButton("1");            enter[13] = new JButton("2");            enter[14] = new JButton("3");            enter[15] = new JButton("=");            enter[16] = new JButton("0");            enter[17] = new JButton(".");            enter[18] = new JButton("+/-");            enter[19] = new JButton("f");                        enter[0].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                    first = 0;                    second = 0;                    select = 0;                    out.setText("0");                }            });                        enter[1].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    throw new UnsupportedOperationException("Not supported yet.");                }            });                         enter[2].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                    select = 4;                    counter = 0;                    out.setText("/");                }            });                          enter[3].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                   select = 3;                   counter = 0;                   out.setText("*");                }            });                           enter[4].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                   if(select == 0){                       first = 7 + (int)(first*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(first));                           }                   else{                       second = 7 + (int)(second*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(second));                   }                }            });                            enter[5].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                     if(select == 0){                       first = 8 + (int)(first*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(first));                           }                   else{                       second = 8 + (int)(first*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(second));                   }                }            });                             enter[6].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                     if(select == 0){                       first = 9 + (int)(first*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(first));                           }                   else{                       second = 9 + (int)(second*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(second));                   }                }            });                              enter[7].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                   select = 2;                   counter = 0;                   out.setText("-");                }            });                               enter[8].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                     if(select == 0){                       first = 4 + (int)(first*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(first));                           }                   else{                       second = 4 + (int)(second*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(second));                   }                }            });                                enter[9].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                     if(select == 0){                       first = 5 + (int)(first*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(first));                           }                   else{                       second = 5 + (int)(first*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(second));                   }                }            });                                 enter[10].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                     if(select == 0){                       first = 6 + (int)(first*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(first));                           }                   else{                       second = 6 + (int)(second*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(second));                   }                }            });                                  enter[11].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                   select = 1;                   counter = 0;                   out.setText("+");                }            });                                   enter[12].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                     if(select == 0){                       first = 1 + (int)(first*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(first));                           }                   else{                       second = 1 + (int)(second*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(second));                   }                }            });                                    enter[13].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                   if(select == 0){                       first = 2 + (int)(first*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(first));                           }                   else{                       second = 2 + (int)(second*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(second));                   }                }            });                                     enter[14].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                   if(select == 0){                       first = 3 + (int)(first*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(first));                           }                   else{                       second = 3 + (int)(second*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(second));                   }                }            });                                      enter[15].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                   switch(select){                       case 1:                           out.setText(String.valueOf(first+second));                           break;                       case 2:                            out.setText(String.valueOf(first-second));                           break;                       case 3:                            out.setText(String.valueOf(first*second));                           break;                       case 4:                            out.setText(String.valueOf(first/second));                           break;                   }                                      first = 0;                   second = 0;                   select = 0;                   counter = 0;                }            });                                       enter[16].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                   if(select == 0){                       first = 0 + (int)(first*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(first));                           }                   else{                       second = 0 + (int)(second*Math.pow(10, counter));                       counter++;                       out.setText(String.valueOf(second));                   }                }            });                                        enter[17].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                                   }            });                                         enter[18].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                   if(select == 0){                                          first = 0 -first;                       out.setText(String.valueOf(first));                   }                                      else {                       second = 0- second;                       out.setText(String.valueOf(second));                   }                }            });                                          enter[19].addActionListener(new ActionListener( ) {                @Override                public void actionPerformed(ActionEvent e) {                    //throw new UnsupportedOperationException("Not supported yet.");                                   }            });                                          for(int i = 0; i < 20; i++){                add(enter[i]);            }                    }    }}

The final running result is:

The interface is ugly. I also feel ugly. It doesn't matter. I tested it a little and it should be okay.