通过使用java的swing、io来实现一个简单记事本，实现打开指定的text文本文件，然后将text文件的内容加载到swing组件中，然后在swing组件中编辑记事本内容，然后同菜单的保存选项将编辑后的内容保存到text文件中。代码如下：
import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.nio.charset.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.joptionpane;
/**
*功能：简单记事本
*2011-12-25
*/
public class simplenotepad implements actionlistener{
private frame frame;
private filedialog fd_load;
private filedialog fd_save;
private textarea ta;
private string file = "";
private menuitem save;
private randomaccessfile raf;
private filechannel fci;
private filelock flock;
private charsetencoder encoder;
private charsetdecoder decoder;
public static void main( string args[]) {
new simplenotepad().init();
}
public void init(){
frame = new frame("my notepad");
menubar mb = new menubar();
menu file = new menu("文件");
menu help = new menu("帮助");
menuitem open = new menuitem("打开");
save = new menuitem("保存");
save.setenabled(false);
file.add(open);
file.add(save);
mb.add(file);
mb.add(help);
frame.setmenubar(mb);
ta = new textarea();
frame.add(ta,"center");
open.addactionlistener(this);
save.addactionlistener(this);
frame.addwindowlistener(new windowadapter(){
public void windowclosing(windowevent e){
system.exit(0);
}
});
frame.setsize(600,400);
frame.setlocation(300,100);
frame.setvisible( true);
fd_load = new filedialog(frame,"打开文件",filedialog.load);
fd_save = new filedialog(frame,"保存文件",filedialog.save);
charset charset = charset.forname(system.getproperty("file.encoding"));
encoder = charset.newencoder();
decoder = charset.newdecoder();
}
public void actionperformed(actionevent e){
string s = e.getactioncommand();
if(s.equals("打开")){
fd_load.setvisible(true);
string d = fd_load.getdirectory();
string f = fd_load.getfile();
if((d != null) && (f != null)){
string destfile = d + f;
if(destfile.equals(file)){
return;
}else{
this.closefile();
file = destfile;
this.loadfile();
}
}
}else if(s.equals("保存")){
this.savefile();
}
}
public void loadfile(){
try{
raf = new randomaccessfile(file,"rw");
fci = raf.getchannel();
flock = fci.trylock();
if(flock == null){
ta.settext("");
joptionpane.showmessagedialog(null,
"文件正在使用中，无法以独占的方式打开！",
"错误提示", joptionpane.error_message);
file = "";
raf.close();
raf = null;
}else{
int length = (int)fci.size();
bytebuffer bb = bytebuffer.allocate(length);
fci.read(bb);
bb.flip();
charbuffer cb = decoder.decode(bb);
ta.settext(cb.tostring());
frame.settitle("my notepad - " + file);
save.setenabled(true);
}
}catch(ioexception e){
e.printstacktrace();
}
}
public void savefile(){
string content = ta.gettext();
try{
charbuffer cb = charbuffer.wrap(content.tochararray());
bytebuffer bb = encoder.encode(cb);
raf.setlength(0);
fci.write(bb);
fci.force(true);
}catch(ioexception e){
e.printstacktrace();
}
}
public void closefile(){
try{
if(flock != null){
flock.release();
}
if(raf != null){
raf.close();
}
file = "";
frame.settitle("my notepad");
save.setenabled(false);
}catch(ioexception e){
e.printstacktrace();
}
}
}
效果图：
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