How To Keep Size Of JTextArea constant?

I'm using an object of JTextArea in my application which deals with sending sms.

I've used a DocumentFilter so as to allow only 160 characters to be typed in the textarea but now, I want the size of the textarea to be constant. it goes on increasing if I keep writing on the same line without pressing 'enter' key or even when I keep on pressing only Enter key. I tried once using 'scrollbar' too but the problem remains same. Suggest me something over this. Below is my code. Please check it.

class Send_sms extends JPanel implements ActionListener,DocumentListener    
{     
    JButton send;  
    JTextArea smst;  
    JLabel title,limit;  
    JPanel mainp,titlep,sendp,wrap,titlewrap,blankp1,blankp2,sendwrap;   
    JScrollPane scroll;  
    Border br,blackbr;  
    Boole开发者_如何学编程an flag = false;  
    PlainDocument plane;
    public static final int LINES = 4;  
    public static final int CHAR_PER_LINE = 40;     
       //character limit 160 for a sms  

    public Send_sms()
        {
        br = BorderFactory.createLineBorder(Color.RED);
        blackbr = BorderFactory.createEtchedBorder(EtchedBorder.RAISED,Color.DARK_GRAY,Color.GRAY);
        setBorder(blackbr);

                title = new JLabel("Enter the text you want to send!");
        title.setFont(new Font("",Font.BOLD,17));
        limit = new JLabel(""+charCount+" Characters");
        smst = new JTextArea(LINES,CHAR_PER_LINE);
        smst.setSize(100,100);
        plane = (PlainDocument)smst.getDocument();
        //adding DocumentSizeFilter 2 keep track of characters entered
        plane.setDocumentFilter(new DocumentSizeFilter(charCount));
        plane.addDocumentListener(this);
        send = new JButton("Send");
        send.setToolTipText("Click Here To Send SMS");
        send.addActionListener(this);

        //scroll = new JScrollPane(smst);
        //scroll.setPreferredSize(new Dimension(200,200));
        //scroll.setVerticalScrollBarPolicy(null);
        //scroll.setHorizontalScrollBarPolicy(null);
        smst.setBorder(br);

        blankp1 = new JPanel();
        blankp2 = new JPanel();
        titlep = new JPanel(new FlowLayout(FlowLayout.CENTER));
        titlewrap = new JPanel(new GridLayout(2,1));
        mainp = new JPanel(new BorderLayout());
        sendwrap = new JPanel(new GridLayout(3,1));
        sendp = new JPanel(new FlowLayout(FlowLayout.CENTER));
        wrap = new JPanel(new BorderLayout());

        titlep.add(title);
        titlewrap.add(titlep);
        titlewrap.add(blankp1);

        sendp.add(send);
        sendwrap.add(limit);
        sendwrap.add(blankp2);
        sendwrap.add(sendp);

        wrap.add(smst,BorderLayout.CENTER); 
        mainp.add(titlewrap,BorderLayout.NORTH);
        mainp.add(wrap,BorderLayout.CENTER);
        mainp.add(sendwrap,BorderLayout.SOUTH);
        add(mainp);


              }

    public void actionPerformed(ActionEvent e)
    {
        Vector<Vector<String>> info = new Vector<Vector<String>> ();
        Vector<String> numbers = new Vector<String>();
        if(e.getSource() == send)
        {
            //Call a function to send he message to all the clients using text
            //charCount = 165;
            String msg = smst.getText();
            if(msg.length() == 0)
                JOptionPane.showMessageDialog(null,"Please Enter Message","Error",JOptionPane.ERROR_MESSAGE);
            else
            {
            //  System.out.println("Message:"+msg);

                Viewdata frame = new Viewdata(msg);

                limit.setText(""+charCount+" Characters");
                charCount = 160;
              } 
        }
    }
    public void insertUpdate(DocumentEvent e)
    {
        System.out.println("The legth:(insert) "+e.getLength());
        for(int i = 0;i<e.getLength(); i++)
        {   
            if(charCount >0)
                charCount--;
            else
                break;
        }
        limit.setText(""+charCount+" Characters");

    }
    public void removeUpdate(DocumentEvent e)
    {
        //System.out.println("The legth(remove): "+e.getLength());
        for(int i = 0;i<e.getLength(); i++)
        {   

            charCount++;

        }
        limit.setText(""+charCount+" Characters");      
    }
    public void changedUpdate(DocumentEvent e)
    {
        //System.out.println("The legth(change): "+e.getLength());

    }   

}//end Send_sms

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Sound like you are creating the text area using

JTextArea textArea = new JTextArea();

When using this format the text area doesn't have a preferred size so it keeps on growing. If you use:

JTextArea textArea = new JTextArea(2, 30);
JScrollPane scrollPane = new JScrollPane( textArea );

Then the text area will have a preferred size of 2 rows and (roughly) 30 columns. As you type when you exceed the preferred width the horizontal scrollbar will appear. Or if you turn on wrapping, then the text will wrap and a vertical scrollbar will appear.

---

you need to specify:

textArea.setColumns (160);
textArea.setLineWrap (true);
textArea.setWrapStyleWord (false); //default

But the real problem is that you allow to input more than 160 characters. You need to create some kind of validator which will skip all inputed characters when there are already 160 characters written.

---

Initialise the textArea with a document that extends PlainDocument and in the insertString method limit the characters to 160