Hi Friend,

Using the setPreferredSize(new Dimension(40,15)); method, you can set the button size in awt in java.

Here is your required code:

import java.awt.*;
import java.awt.event.*;
import java.util.regex.*;
class ButtonSize extends Frame{
    Label l;
    ButtonSize(){
        Label lab=new Label("Enter number to find its factorial: ");
        final TextField text=new TextField(20);
        Button b=new Button("Find");
        Panel p=new Panel();
        l=new Label();
        Panel pan=new Panel();
        pan.add(l);
        b.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e){
                String input=text.getText();
    Pattern p = Pattern.compile("[A-Z,a-z,&%$#@!()*^]");
    Matcher m = p.matcher(input);
if(m.find()){
    l.setText("*Enter only numeric value!");
    l.setSize(250,20);
    l.setForeground(Color.RED);
    ltext.setText("");
    }
else if(input.equals("")){
    l.setText("*Enter value!");
    l.setSize(250,20);
    l.setForeground(Color.RED);
    }
else{

    int num=Integer.parseInt(input);
    long fac=num;
    for(int i=num;i>1;i--){
        fac=fac*(i-1);
         }
         System.out.println(fac);
    l.setText("Factorial Of Number "+input+" is: "+Long.toString(fac));
    l.setSize(250,20);
    l.setForeground(Color.BLUE);
}
            }
        });
        p.add(lab);
        p.add(text);
        p.add(b);
        b.setPreferredSize(new Dimension(40,15));     
        add(p,BorderLayout.NORTH);
        add(pan,BorderLayout.SOUTH);
        pack();
        setVisible(true);
    }
    public static void main(String[] args){
        new ButtonSize();
    }
}

Thanks