letter to number converter in phone key pad format

Question

im having trouble in my program. the instruction is to convert the letters that the user inputed and output its corresponding number equivalent in a phone keypad. and i keep having the same error: incompatible types

this is what i have so far:

import java.awt.Color;
import java.awt.Container;
import java.awt.FlowLayout;
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.JTextField;
import java.text.DecimalFormat;

public class phone extends JFrame implements ActionListener
{
    JLabel num = new JLabel("Telephone Number(phones Format): ");   
    JButton btn1 = new JButton("   Convert   ");
    JLabel tel = new JLabel("Number Format: ");


    JTextField txt1 = new JTextField(10);
    JTextField txt2 = new JTextField(10);

    Container c = getContentPane();

    public phone()
    {
        super("Telephone");
        c.setLayout(new FlowLayout());

        c.add(num);
        c.add(txt1);
        c.add(btn1);
        c.add(tel);
        c.add(txt2);

        btn1.addActionListener(this);

        this.setSize(160,260);
        this.setVisible(true);
        this.setDefaultCloseOperation(3);
        this.setResizable(false);                   
    }

    public void actionPerformed(ActionEvent a)
    {
        String txt=txt1.getText();
    int x=0;
        String [] phones = new String[8];
        for( int i = 0; i<=8;i++)
        {

    if (phones=="A" || phones=="B" || phones== "C")
         {
            x=2;
         }

         else if(phones=="D" || phones=="E" || phones== "F")
         {
           x=3;
         }

        else if (phones=="G" || phones=="H" || phones== "I")
         {
           x=4;   
         }
         else if (phones=="J" || phones=="K" || phones== "L")
         {
            x=5;    
         }
         else if (phones=="M" || phones=="N" || phones== "O")
         {
            x=6;    
         }    

        else if (phones=="P" || phones=="Q" || phones== "R" || phones== "S")
         {
           x=7;    
         }    

        else if (phones=="T" || phones=="U" || phones== "V")
         {
            x=8;    
         }    

         else if (phones=="W" || phones=="X" || phones== "Y" || phones== "Z")
         {
            x=9;    
         }    


        }
        txt2.setText(x);
    }
    public static void main(String args[])
    {
        phone M = new phone();
    }
}

update:

i manage to do some changes but my problem now is the formatting part.

the format should be: ###-####

here is the update:

import java.awt.Color;
import java.awt.Container;
import java.awt.FlowLayout;
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.JTextField;
import java.text.DecimalFormat;

public class phone extends JFrame implements ActionListener
{
    JLabel num = new JLabel("Telephone Number(txt Format): ");  
    JButton btn1 = new JButton("   Convert   ");
    JLabel tel = new JLabel("Number Format: ");


    JTextField txt1 = new JTextField(10);
    JTextField txt2 = new JTextField(10);

    Container c = getContentPane();

    public phone()
    {
        super("Telephone");
        c.setLayout(new FlowLayout());

        c.add(num);
        c.add(txt1);
        c.add(btn1);
        c.add(tel);
        c.add(txt2);

        btn1.addActionListener(this);

        this.setSize(160,260);
        this.setVisible(true);
        this.setDefaultCloseOperation(3);
        this.setResizable(false);                   
    }

    public void actionPerformed(ActionEvent a)
    {
        String pattern="###-####";
        DecimalFormat df=new DecimalFormat(pattern);
        String txt= txt1.getText();
           char[] data = txt.toCharArray();
        for (int i=0; i<data.length; ++i) {
            char c = data[i];
            c = Character.toLowerCase(c);
            switch (c) {
                case 'a':
                case 'b':
                case 'c':   data[i] = '2';
                            break;
                case 'd':
                case 'e':
                case 'f':   data[i] = '3';
                            break;
                case 'g':
                case 'h':
                case 'i':   data[i] = '4';
                            break;
                case 'j':
                case 'k':
                case 'l':   data[i] = '5';
                            break;
                case 'm':
                case 'n':
                case 'o':   data[i] = '6';
                            break;
                case 'p':
                case 'q':
                case 'r':
                case 's':   data[i] = '7';
                            break;
                case 't':
                case 'u':
                case 'v':   data[i] = '8';
                            break;
                case 'w':
                case 'x':
                case 'y':
                case 'z':   data[i] = '9';
            }
        }
        String l=df.format(String.valueOf(data));

        txt2.setText(l);
    }
    public static void main(String args[])
    {
        phone M = new phone();
    }
}

Answer 1

phones is a String array (String []), not a String. You are trying to compare it to a String, and that is why you are getting the incompatible types error

A few other notes/problems:

• Your phone class should be named Phone. "Class names should be nouns, in mixed case with the first letter of each internal word capitalized"
• phones=="A". String comparison does not work like this. See this StackOverflow question for plenty more details about why this does not work and how shyou should compare strings
• txt2.setText(x); will give you another error because x is an int, and the method takes a String as input
• this.setDefaultCloseOperation(3); - You should use 1 of the constants from WindowConstants rather than than the hardcoded 3. This would translate into this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);