Determine when a component is added or removed from a container

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COMPLETE SOURCE CODE FOR : DetermineWhenAComponentIsAddOrRemove.java
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import java.awt.Frame;//import Frame class into program
import java.awt.Panel;//import Panel class into program
import java.awt.Button;//import Button class into program
import java.awt.Label;//import Label class into program
import java.awt.Component;//import Component class into program

import java.awt.event.ContainerListener;//import ContainerListener class into program
import java.awt.event.ContainerAdapter;//import ContainerAdapter class into program
import java.awt.event.ContainerEvent;//import ContainerEvent class into program

import java.awt.event.WindowListener;//import WindowListener class into program
import java.awt.event.WindowAdapter;//import WindowAdapter class into program
import java.awt.event.WindowEvent;//import WindowEvent class into program

import java.awt.event.ActionListener;//import ActionListener class into program
import java.awt.event.ActionEvent;//import ActionEvent class into program

import java.awt.BorderLayout;//import BorderLayout class into program
import java.awt.FlowLayout;//import FlowLayout class into program

import java.awt.Color;//import Color class into program

import javax.swing.JOptionPane;//import JOptionPane class into program

public class DetermineWhenAComponentIsAddOrRemove implements ActionListener
{
 //Initiate Frame(a) object
 Frame a=new Frame("DETERMINE WHEN A COMPONENT IS ADD OR REMOVE");
 //Initiate Button(b) object
 Button b=new Button("CLICK HERE TO ADD NEW COMPONENT(A LABEL)");
 //Initiate Button(d) object
 Button d=new Button("CLICK HERE TO REMOVE NEW INSERTED COMPONENT");
 //Initiate Panel(c) object
 Panel c=new Panel();
 
 public DetermineWhenAComponentIsAddOrRemove()
 {
  //Set layout for Frame(a)
  a.setLayout(new BorderLayout());
  
  //Listen when someone click at Frame(a) close button
  WindowListener wl=new WindowAdapter()
  {
   public void windowClosing(WindowEvent evt)
   {
    System.exit(0);
   }
  };
  
  //Listen when a component is added or removed from Panel(c)
  ContainerListener cl=new ContainerAdapter()
  {
   public void componentAdded(ContainerEvent evt)
   {
    JOptionPane.showMessageDialog(null,"A COMPONENT ADDED");
   }
   
   public void componentRemoved(ContainerEvent evt)
   {
    JOptionPane.showMessageDialog(null,"A COMPONENT REMOVED");
   } 
  };
  
  //Label at the top of Frame(a)
  Label e=new Label("PANEL WITH BLUE COLOR AT THE CENTER IS A CONTAINER");
  //Make Label's allignment to center
  e.setAlignment(Label.CENTER);
  //Add Label(e) to Frame(a)
  a.add(e,BorderLayout.NORTH);
  
  //Add ContainerListener to Panel(c)
  c.addContainerListener(cl);
  //Set background color(blue) to Panel(c)
  c.setBackground(Color.BLUE);
  //Add Panel(c) to Frame(a)
  a.add(c,BorderLayout.CENTER);
  
  //Panel to place Button(b and d)
  Panel f=new Panel();
  //Set layout for panel(f)
  f.setLayout(new FlowLayout());
  //Add ActionListener to Button(b and d)
  b.addActionListener(this);
  d.addActionListener(this);
  //Add button(b and d) to Panel(f)
  f.add(b);
  f.add(d);
  //Add Panel(f) to Frame(a)
  a.add(f,BorderLayout.SOUTH);
  
  //Add WindowListener to Frame(a)
  a.addWindowListener(wl);
  //Set Frame(a) size to 800pixel width and 600pixel height
  a.setSize(800,600);
  //Set Frame(a) to visible
  a.setVisible(true);
 }
 
 //Action that must do by Button(b and d)
 public void actionPerformed(ActionEvent evt)
 {
  //Action for Button b
  if(evt.getSource()==b)
  {
   c.add(new Label("NEW LABEL"));
   c.validate();
   a.validate();
  }
  
  //Action for Button d
  if(evt.getSource()==d)
  {
   Component[]storeAllComponent=c.getComponents();
   if(storeAllComponent.length!=0)
   {
    int numbersOfComponent=storeAllComponent.length;
    int indexForRemoveComponent=numbersOfComponent-1;
    c.remove(indexForRemoveComponent);
    c.validate();
    a.validate();
   }
  }
 }
 
 //MAIN METHOD
 public static void main(String[]args)
 {
  DetermineWhenAComponentIsAddOrRemove myObject=new DetermineWhenAComponentIsAddOrRemove();
 }
}

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JUST COMPILE AND EXECUTE IT
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Get child components from a container

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COMPLETE SOURCE CODE FOR : GetChildComponentOfaContainer.java
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import java.awt.Frame;//IMPORT FRAME CLASS INTO THIS PROGRAM
import java.awt.Label;//IMPORT LABEL CLASS INTO THIS PROGRAM
import java.awt.TextField;//IMPORT TEXTFIELD CLASS INTO THIS PROGRAM
import java.awt.Button;//IMPORT BUTTON CLASS INTO THIS PROGRAM
import java.awt.Panel;//IMPORT PANEL CLASS INTO THIS PROGRAM
import java.awt.Component;//IMPORT COMPONENT CLASS INTO THIS PROGRAM

import java.awt.event.WindowListener;//IMPORT WINDOWLISTENER CLASS INTO THIS PROGRAM
import java.awt.event.WindowAdapter;//IMPORT WINDOWADAPTER CLASS INTO THIS PROGRAM
import java.awt.event.WindowEvent;//IMPORT WINDOWEVENT CLASS INTO THIS PROGRAM
import java.awt.event.ActionListener;//IMPORT ACTIONLISTENER CLASS INTO THIS PROGRAM
import java.awt.event.ActionEvent;//IMPORT ACTIONEVENT CLASS INTO THIS PROGRAM

import java.awt.FlowLayout;//IMPORT FLOWLAYOUT CLASS INTO THIS PROGRAM
import java.awt.BorderLayout;//IMPORT BORDERLAYOUT CLASS INTO THIS PROGRAM

import java.awt.Color;//IMPORT COLOR CLASS INTO THIS PROGRAM

import javax.swing.JOptionPane;//IMPORT JOPTIONPANE CLASS INTO THIS PROGRAM

public class GetChildComponentOfaContainer implements ActionListener
{
 Frame a=new Frame("GET CHILD COMPONENT IN CONTAINER");
 Panel b=new Panel();
 Button d=new Button("ADD NEW COMPONENT INTO MONSTER (A LABEL)");
 Button c=new Button("CLICK HERE TO SEE NUMBERS OF COMPONENTS IN MONSTER");
 
 public GetChildComponentOfaContainer()
 {
  //SET LAYOUT FOR FRAME a
  a.setLayout(new BorderLayout());
  
  //LISTEN TO WINDOW CLOSING EVENT FOR a
  //WHEN SOMEONE CLICK CLOSE BUTTON, THIS APPLICATION WILL TERMINATE.
  WindowListener wl=new WindowAdapter()
  {
   public void windowClosing(WindowEvent evt)
   {
    System.exit(0);
   }
  };
  
  //PANEL b, TO PLACE COMPONENT
  b.setBackground(Color.YELLOW);
  b.add(new Label("COMPONENT 1 : A LABEL"));
  b.add(new TextField("COMPONENT 2 : A TEXTFIELD"));
  b.add(new Button("COMPONENT 3 : A BUTTON"));
  a.add(b,BorderLayout.CENTER);
  
  //ADD ACTIONLISTENER FOR BUTTON TO MAKE IT FUNCTION WHEN SOMEONE CLICK.
  d.addActionListener(this);
  c.addActionListener(this);
  
  //PLACE BOTH THE BUTTONS INTO A CONTAINER AND AFTER THAT PLACE THE CONTAINER INTO a
  Panel e=new Panel();
  e.add(c);
  e.add(d);
  a.add(e,BorderLayout.SOUTH);
  
  //LABEL AT THE TOP OF a
  Label f=new Label("YELLOW AREA IS A PANEL WITH NAME MONSTER");
  f.setAlignment(Label.CENTER);
  a.add(f,BorderLayout.NORTH);
  
  a.addWindowListener(wl);
  a.setSize(800,600);
  a.setVisible(true);
 }
 
 //ALL BUTTON ACTION IS HERE
 public void actionPerformed(ActionEvent evt)
 {
  //ACTION FOR BUTTON "ADD NEW COMPONENT INTO MONSTER (A LABEL)"
  if(evt.getSource()==d)
  {
   b.add(new Label("NEW"));
   //The validate method is used to cause a container to lay out its subcomponents again.
   //So you can see the latest label("NEW") that you add.
   b.validate();
   a.validate();
  }
  
  //ACTION FOR BUTTON "CLICK HERE TO SEE NUMBERS OF COMPONENTS IN MONSTER"
  if(evt.getSource()==c)
  {
   Component[]arrayToStoreAllComponent=b.getComponents();//STORE ALL COMPONENT IN b IN AN ARRAY
   int numbersOfComponent=arrayToStoreAllComponent.length;//GET ARRAY LENGTH BECAUSE IT SAME TO NUMBERS OF COMPONENT
   JOptionPane.showMessageDialog(null,"NUMBERS OF CURRENT COMPONENT IN MONSTER IS : "+numbersOfComponent);
  }
 }
 
 //MAIN METHOD
 public static void main(String[]args)
 {
  GetChildComponentOfaContainer myObject=new GetChildComponentOfaContainer();
 }
}

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JUST COMPILE AND EXECUTE IT
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