bookmarklist.java

JAVA图形用户界面设计与实例+(源代码)

//BookmarkList.java
//List of sites bookmarked by the user, derived from List

import java.util.*;
import java.io.*;

public class BookmarkList extends List {

    public static final String BFILE = "bookmark.lis";

    
    public BookmarkList() {//Constructor
        super();
        readIntoList();
    }

   
    public void add(String s) {//Overrides the add method in List 
        super.add(s);
        writeToFile();
    }

    public void startupAdd(String s)
   {//Adds bookmarks from the file into the list without writing to disk

        super.add(s);
    }

  
//********************************************************************************  
    public void remove(String s) throws Exception {//Removes an item from the list
        WebNode holder = head;
        boolean isFound = false;

        if(isEmpty())
            throw new Exception("记录为空");

        else if ((holder.getURL()).equals(s)){
            head = holder.getNext();
            size--;
            writeToFile();
            isFound = true;
        }

        else {
            while ((holder != null) && (!isFound)){
                if ((holder.getNext().getURL()).equals(s)) {
                    holder.setNext(holder.getNext().getNext());
                    isFound = true;
                    size--;
                    writeToFile();
                }
                else{
                    holder = holder.getNext();
                }
            }
        }


        if (!isFound) {
            throw new Exception("No match found!");
        }
    }

//********************************************************************************  
    
    private void writeToFile() {//将list写入 a file
        try {
            FileOutputStream fOut = new FileOutputStream(BFILE);
            for (WebNode x = head; x != null; x = x.getNext()) {
                fOut.write(x.getURL().getBytes());
                fOut.write('\n');
            }
            fOut.close();
        }

        catch (Exception e) {
            new PopupDialog("文件错误", "不能写入文件");
        }
    }

    private void readIntoList() {//从file里面读取list
        try {
            FileInputStream fIn = new FileInputStream(new File(BFILE));
            byte bt[] = new byte[(int) (new File(BFILE)).length()];
            fIn.read(bt);
            String s = new String(bt);
            StringTokenizer st = new StringTokenizer(s, "\n");
            while(st.hasMoreTokens())
                startupAdd(st.nextToken());
            fIn.close();
        }

        catch(Exception e) {

        }
    }

//********************************************************************************

    public String returnURL(int loc) {
        WebNode wn = head;
        for (int x = 0; x < loc; x++)
            wn = wn.getNext();

        return wn.getURL();
    }
    
}