java - Swing text field visibility issue -

i trying make frame , add text field inside it. used jtextfield. it's not appearing.

code

import java.awt.*; import javax.swing.*;  class tst {     jframe f;     jtextfield tf;      public tst()     {         f=new jframe();         tf=new jtextfield(10);         f.setsize(400,400);         f.add(tf);         f.setlayout(null);         f.setvisible(true);     }      public static void main(string s[])     {         new tst();     } } 

if don't want use layout manager, need set bounds using jtextfield's setbounds(x, y, width, height) method, x , y position of textfield in jframe:

tf.setbounds(100 , 100 , 100 , 20 ); 

first set layout frame, add elements , components it, in full code:

import javax.swing.*;  class tst {     public tst()     {         jtextfield tf = new jtextfield(10);         tf.setbounds(100 , 100 , 100 , 20 );          jframe f = new jframe();          f.setsize(400, 400);         f.setlayout(null);         f.setvisible(true);         f.add(tf);          f.setdefaultcloseoperation(jframe.exit_on_close);     }      public static void main(string s[])     {         new tst();     } }