Creating a Sub JMenuItem

Program Description:

The Java Program below demonstrates how to add a JMenu under a JMenu and create a JMenuItem as a sub-menu. "File" is the parent JMenu, "Main Menu" is the child JMenu, and the "Sub Menu 1 - 5" are the JMenuItem. You have to take note that JMenuItem can only be used once in every JMenu so this code won't work:

subItems = new JMenuItem[5];
     
     for(int count=0; count<subItems.length; count++){
      subItems[count] = new JMenuItem("Sub Menu "+(count+1));
      mainItem[count].add(subItems[count]); //Adding JMenuItem "subItems" in the JMenu "mainItem"
     }

this will create an error on line 5 because you are assigning the JMenuItem on every JMenu. The rule is, JMenuItem(s) can only be assigned in to one JMenu so the code goes like this:

subItems = new JMenuItem[5];
     
     for(int count=0; count<subItems.length; count++){
      subItems[count] = new JMenuItem("Sub Menu "+(count+1));
      mainItem[0].add(subItems[count]); //Adding JMenuItem "subItems" in the JMenu "mainItem"
     }

You have to specify a JMenu where the JMenuItem is added.

Output:

Code:

/**
 * File: creatingSubJMenuItem.java
 * Tiltle: Creating a Sub JMenuItem
 * Author: http://java-code-complete.blogspot.com/
 */

//Java Core Package
import javax.swing.*;
//Java Extension Package
import java.awt.*;

public class creatingSubJMenuItem extends JFrame {
 
 //Initializing program components
 private JMenu menus;
 private JMenuBar bar;
 private JMenu mainItem[];
 private JMenuItem subItems[];

 //Setting up GUI
    public creatingSubJMenuItem() {
     
     //Setting up the Title of the Window
     super("Creating a Sub JMenuItem");

     //Set Size of the Window (WIDTH, HEIGHT)
     setSize(350,200);

     //Exit Property of the Window
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  
  //Constructing JMenu "File" with mnemonic 'F'
     menus = new JMenu("File");
     menus.setMnemonic('F');
     
     //Constructing main JMenu and add it in JMenu "File"
     mainItem = new JMenu[1];
     
     for(int count=0; count<mainItem.length; count++){
      mainItem[count] = new JMenu("Main Menu "+(count+1));
      menus.add(mainItem[count]); //Adding JMenu "mainItem" in the JMenu "File"
     }
     
     //Constructing JMenuItem "subItems" as a Sub Menu to the main JMenu
     subItems = new JMenuItem[5];
     
     for(int count=0; count<subItems.length; count++){
      subItems[count] = new JMenuItem("Sub Menu "+(count+1));
      mainItem[0].add(subItems[count]); //Adding JMenuItem "subItems" in the JMenu "mainItem"
     }
     
     //Constructing JMenuBar
     bar = new JMenuBar();
     bar.add(menus); //Adding the JMenu "File" in the JMenuBar
     
     //Setting up the JMenuBar in the container
     setJMenuBar(bar);

     //Setting up the container ready for the components to be added.
     Container pane = getContentPane();
     setContentPane(pane);

     /**Set all the Components Visible.
      * If it is set to "false", the components in the container will not be visible.
      */
     setVisible(true);
    }
    
 //Main Method
    public static void main (String[] args) {
     creatingSubJMenuItem csjmi = new creatingSubJMenuItem();
 }
}

Important Part of the Program:

//Constructing JMenu "File" with mnemonic 'F'
     menus = new JMenu("File");
     menus.setMnemonic('F');
     
     //Constructing main JMenu and add it in JMenu "File"
     mainItem = new JMenu[1];
     
     for(int count=0; count<mainItem.length; count++){
      mainItem[count] = new JMenu("Main Menu "+(count+1));
      menus.add(mainItem[count]); //Adding JMenu "mainItem" in the JMenu "File"
     }
     
     //Constructing JMenuItem "subItems" as a Sub Menu to the main JMenu
     subItems = new JMenuItem[5];
     
     for(int count=0; count<subItems.length; count++){
      subItems[count] = new JMenuItem("Sub Menu "+(count+1));
      mainItem[0].add(subItems[count]); //Adding JMenuItem "subItems" in the JMenu "mainItem"
     }
     
     //Constructing JMenuBar
     bar = new JMenuBar();
     bar.add(menus); //Adding the JMenu "File" in the JMenuBar
     
     //Setting up the JMenuBar in the container
     setJMenuBar(bar);