swing - How can we add JScrollPane on JTextArea in java? -

can tell me problem in following program? want fit jscrollpane on jtextarea when add jtextarea not visible.

import javax.swing.*; import java.awt.*; import java.awt.event.*;  class area extends jframe {     private jtextarea ta;     private jtextfield tf;     jscrollpane jp;      public area()     {        super("text area");        tf=new jtextfield();        tf.setbounds(100,350,300,30);        add(tf);        ta=new jtextarea();        ta.setbounds(100,100,300,200);        jp= new jscrollpane(ta);        add(jp);        setlayout(null);        setsize(500,500);        setvisible(true);        setdefaultcloseoperation(jframe.exit_on_close);    }     public static void main(string...s)    {       new area();    } } 

i see several problems:

• don't use null layout; use real layout.

• the default layout of jframe borderlayout; default position center; 1 component can occupy position @ time; example below uses north & center.

• use appropriate constructor parameters size text components initially.

• the scrollbar appear automatically whenever scrollpane smaller enclosed component; resize frame see effect.

• as shown here, frame's size made smaller effect.

• see initial threads.

import java.awt.borderlayout; import java.awt.eventqueue; import javax.swing.jframe; import javax.swing.jscrollpane; import javax.swing.jtextarea; import javax.swing.jtextfield;  /** @see https://stackoverflow.com/a/19215436/230513 */ public class area extends jframe {      public area() {         super("text area");         setdefaultcloseoperation(jframe.exit_on_close);         jtextfield tf = new jtextfield(12);         add(tf, borderlayout.north);         jtextarea ta = new jtextarea(24, 12);         jscrollpane jp = new jscrollpane(ta);         add(jp, borderlayout.center);         pack();         // arbitrary size make vertical scrollbar appear         setsize(240, 240);         setlocationbyplatform(true);         setvisible(true);     }      public static void main(string[] args) {         eventqueue.invokelater(new runnable() {             @override             public void run() {                 new area();             }         });     } }