MenuMnemonicOnTheFly.java

package eu.irreality.age.windowing;

import java.awt.Component;
import java.util.StringTokenizer;
import java.util.Vector;

import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.MenuElement;

/** 
 * This is a utility class which can be used to set the mnemonics of all the items 
 * in a menubar on the fly. 
 */ 
public class MenuMnemonicOnTheFly 
{ 
    // 
    //This method sets mnemonic of all the items in the menubar 
    // 
    public static void setMnemonics(JMenuBar mb) 
    { 
        MenuElement[] MenuElements = mb.getSubElements(); 
        int num = MenuElements.length; 
        if (0 == num) return; 

        setMnemonicForTopLevel(mb); 
        for (int i = 0; i < num; ++i) 
        { 
            if (!(MenuElements[i] instanceof JMenu)) continue; 
            setMnemonic((JMenu) MenuElements[i]); 
        } 
    } 

    // 
    //This method sets mnemonic of all the top level menus in the menubar 
    // 
    private static void setMnemonicForTopLevel(JMenuBar mb) 
    { 
        MenuElement[] MenuElements = mb.getSubElements(); 
        int num = MenuElements.length; 
        if (0 == num) return; 

        char mnemonics[] = new char[num]; 

        for (int i = 0; i < num; ++i) 
        { 
            if (!(MenuElements[i] instanceof JMenu)) continue; 
            JMenu menu = (JMenu) MenuElements[i]; 

            String text = menu.getText(); 
            char mnemonic = getMnemonic(text, mnemonics); 
            if (' ' != mnemonic) 
            { 
                menu.setMnemonic(mnemonic); 
                mnemonics[i] = mnemonic; 
            } 
        } 
    } 

    // 
    // This method sets mnemonic of the menuitems and submenus of a given menu. 
    // To set different Mnemonic of each item it firsr checks first character of the all the words then the second , third 
    // and so on till a unique character is found. 
    private static void setMnemonic(JMenu jm) 
    { 
        Component mcomps[] = jm.getMenuComponents(); 
        int num = mcomps.length; 

        if (0 == num) return; 

        char mnemonics[] = new char[num]; 

        for (int i = 0; i < num; ++i) 
        { 
            if (!(mcomps[i] instanceof JMenuItem)) continue; 
            JMenuItem menuitem = (JMenuItem) mcomps[i]; 

            String text = menuitem.getText(); 
            char mnemonic = getMnemonic(text, mnemonics); 
            if (' ' != mnemonic) 
            { 
                menuitem.setMnemonic(mnemonic); 
                mnemonics[i] = mnemonic; 
            } 
            if (menuitem instanceof JMenu) 
                setMnemonic((JMenu) menuitem); 
        } 
    } 

    private static char getMnemonic(String text, char[] mnemonics) 
    { 
        Vector words = new Vector(); 
        StringTokenizer t = new StringTokenizer(text); 
        int maxsize = 0; 

        while (t.hasMoreTokens()) 
        { 
            String word = (String) t.nextToken(); 
            if (word.length() > maxsize) maxsize = word.length(); 
            words.addElement(word); 
        } 
        words.trimToSize(); 

        for (int i = 0; i < maxsize; ++i) 
        { 
            char mnemonic = getMnemonic(words, mnemonics, i); 
            if (' ' != mnemonic) 
                return mnemonic; 
        } 

        return ' '; 
    } 

    private static char getMnemonic(Vector words, char[] mnemonics, int index) 
    { 
        int numwords = words.size(); 

        for (int i = 0; i < numwords; ++i) 
        { 
            String word = (String) words.elementAt(i); 
            if (index >= word.length()) continue; 

            char c = word.charAt(index); 
            if (!isMnemonicExists(c, mnemonics)) return c; 
        } 
        return ' '; 
    } 

    private static boolean isMnemonicExists(char c, char[] mnemonics) 
    { 
        int num = mnemonics.length; 
        for (int i = 0; i < num; ++i) 
            if (mnemonics[i] == c) return true; 
        return false; 
    } 
}