//都是从新手过来的,以下代码供参考
//1.
public?class?BankAccount?{
private?static?String?acctnum;
private?static?double?money;
private?static?void?showAcct()?{
System.out.println("账号为:?"?+?acctnum);
}
private?static?void?showMoney()?{
System.out.println("余额为:?"?+?money);
public?BankAccount(String?acc,?double?m)?{
this.acctnum?=?acc;
this.money?=?m;
public?static?void?main(String[]?args)?{
ba.showAcct();
ba.showMoney();
public?class?Triangle?{
private?static?float?a;
private?static?float?b;
private?static?float?c;
public?Triangle(float?a,?float?b,?float?c)?{
this.a?=?a;
this.b?=?b;
this.c?=?c;
public?static?boolean?judgeTriangle(float?a,?float?b,?float?c)?{
if?((a?Math.abs(b?-?c)?a?b?+?c)
(b?Math.abs(a?-?c)?b?a?+?c)
(c?Math.abs(a?-?b)?c?a?+?b))
return?true;
else
return?false;
public?float?getCircumference()?{
return?this.a?+?this.b?+?this.c;
public?class?TestTriangle?{
System.out.print("能够成三角形,周长为:?");
System.out.println("不能构成三角形");
源文件编译后的字节码是以CAFE BABY开头的二进制文件.需要JVM才能读懂.后缀为.class
一般来说,一个类对应一个字节码文件,内部类编译后也会生成一个单独的字节码文件.字节码文件是以类名来命名（标识）的.
一些相关的字节码文件可以按照包结构打包成jar文件.jar文件和zip文件差不多.
java程序一般都会依赖很多的jar文件,比如最基本的rt.jar.
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.awt.datatransfer.*;
class MyMenuBar extends MenuBar{
public MyMenuBar(Frame parent){
parent.setMenuBar(this);
public void addMenus(String [] menus){
for(int i=0;imenus.length;i++)
add(new Menu(menus[i]));
public void addMenuItems(int menuNumber,String[] items){
for(int i=0;iitems.length;i++){
if(items[i]!=null)
getMenu(menuNumber).add(new MenuItem(items[i]));
else getMenu(menuNumber).addSeparator();
public void addActionListener(ActionListener al){
for(int i=0;igetMenuCount();i++)
for(int j=0;jgetMenu(i).getItemCount();j++)
getMenu(i).getItem(j).addActionListener(al);
class MyFile{
private FileDialog fDlg;
public MyFile(Frame parent){
fDlg=new FileDialog(parent,"",FileDialog.LOAD);
private String getPath(){
return fDlg.getDirectory()+"\\"+fDlg.getFile();
public String getData() throws IOException{
fDlg.setTitle("打开");
fDlg.setMode(FileDialog.LOAD);
fDlg.setVisible(true);
BufferedReader br=new BufferedReader(new FileReader(getPath()));
StringBuffer sb=new StringBuffer();
String aline;
while((aline=br.readLine())!=null)
sb.append(aline+'\n');
br.close();
return sb.toString();
public void setData(String data) throws IOException{
fDlg.setTitle("保存");
fDlg.setMode(FileDialog.SAVE);
BufferedWriter bw=new BufferedWriter(new FileWriter(getPath()));
bw.write(data);
bw.close();
class MyClipboard{
private Clipboard cb;
public MyClipboard(){
cb=Toolkit.getDefaultToolkit().getSystemClipboard();
public void setData(String data){
cb.setContents(new StringSelection(data),null);
public String getData(){
Transferable content=cb.getContents(null);
try{
return (String) content.getTransferData(DataFlavor.stringFlavor);
//DataFlavor.stringFlavor会将剪贴板中的字符串转换成Unicode码形式的String对象.
//DataFlavor类是与存储在剪贴板上的数据的形式有关的类.
}catch(Exception ue){}
return null;
class MyFindDialog extends Dialog implements ActionListener{
private Label lFind=new Label("查找字符串");
private Label lReplace=new Label("替换字符串");
private TextField tFind=new TextField(10);
private TextField tReplace=new TextField(10);
private Button bFind=new Button("查找");
private Button bReplace=new Button("替换");
private TextArea ta;
public MyFindDialog(Frame owner,TextArea ta){
super(owner,"查找",false);
this.ta=ta;
setLayout(null);
add(lFind);
add(tFind);
add(bFind);
add(lReplace);
add(tReplace);
add(bReplace);
setResizable(false);
bFind.addActionListener(this);
bReplace.addActionListener(this);
addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e){
MyFindDialog.this.dispose();
});
}//构造函数结束
public void showFind(){
setTitle("查找");
setVisible(true);
public void showReplace(){
setTitle("查找替换");
private void find(){
String text=ta.getText();
String str=tFind.getText();
int end=text.length();
int len=str.length();
int start=ta.getSelectionEnd();
if(start==end) start=0;
for(;start=end-len;start++){
if(text.substring(start,start+len).equals(str)){
ta.setSelectionStart(start);
ta.setSelectionEnd(start+len);
return;
//若找不到待查字符串,则将光标置于末尾
ta.setSelectionStart(end);
ta.setSelectionEnd(end);
public Button getBFind() {
return bFind;
private void replace(){
String str=tReplace.getText();
if(ta.getSelectedText().equals(tFind.getText()))
ta.replaceRange(str,ta.getSelectionStart(),ta.getSelectionEnd());
else find();
public void actionPerformed(ActionEvent e) {
if(e.getSource()==bFind)
find();
else if(e.getSource()==bReplace)
replace();
public class MyMemo extends Frame implements ActionListener{
private MyFile mf=new MyFile(this);//MyFile对象
private MyClipboard cb=new MyClipboard();
private MyFindDialog findDlg=new MyFindDialog(this,editor);
public MyMemo(String title){ //构造函数
super(title);
MyMenuBar mb=new MyMenuBar(this);
//添加需要的菜单及菜单项
mb.addMenuItems(0,new String[]{"新建","打开","保存",null,"全选"});
mb.addMenuItems(1,new String[]{"剪贴","复制","粘贴","清除",null,"全选"});
add(editor); //为菜单项注册动作时间监听器
mb.addActionListener(this);
MyMemo.this.dispose();
}); //分号不能忘了
} //构造函数完
public void actionPerformed(ActionEvent e){
String selected=e.getActionCommand(); //获取菜单项标题
if(selected.equals("新建"))
editor.setText("");
else if(selected.equals("打开")){
editor.setText(mf.getData());
}catch(IOException ie){}
else if(selected.equals("保存")){
mf.setData(editor.getText());
else if(selected.equals("退出")){
dispose();
else if(selected.equals("剪贴")){
//将选中的字符串复制到剪贴板中并清除字符串
cb.setData(editor.getSelectedText());
editor.replaceRange("",editor.getSelectionStart(),editor.getSelectionEnd());
else if(selected.equals("复制")){
else if(selected.equals("粘贴")){
String str=cb.getData();
editor.replaceRange(str,editor.getSelectionStart(),editor.getSelectionEnd());
//粘贴在光标位置
else if(selected.equals("清除")){
else if(selected.equals("全选")){
editor.setSelectionStart(0);
editor.setSelectionEnd(editor.getText().length());
else if(selected.equals("查找")){
findDlg.showFind();
else if(selected.equals("查找替换")){
findDlg.showReplace();
public static void main(String[] args){
MyMemo memo=new MyMemo("记事本");
memo.setVisible(true);
给你个小例子,已经添加注释了.自己运行下看看效果,满意的话记得结贴子！
import java.awt.BorderLayout;
import java.awt.CheckboxMenuItem;
import java.awt.Frame;
import java.awt.Menu;
import java.awt.MenuBar;
import java.awt.MenuItem;
import java.awt.TextArea;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
public class TestMenu extends Frame implements ActionListener{
TextArea ta; //文本区
MenuBar mb; //MenuBar 类封装绑定到框架的菜单栏的
Menu mnFile,mnEdit,mnFormat,mnHelp; //从菜单栏部署的下拉式菜单组件
MenuItem miNew,miOpen,miSave,miSaveAs,miExit,miFont; //菜单中的所有项必须属于类 MenuItem 或其子类之一
CheckboxMenuItem miBinary; //一个可包括在菜单中的复选框
public TestMenu(){
super("记事本"); //调用父类构造方法
/*
* BorderLayout边框布局
* 添加文本区到Frame,BorderLayout.CENTER是居中位置
* */
add(ta,BorderLayout.CENTER);
mb = new MenuBar(); //创建菜单栏对象
* 创建菜单,指定菜单名
mnFile= new Menu("文件");
mnFormat= new Menu("格式");
mnHelp= new Menu("帮助");
* 创建子菜单,并指定名称
miNew= new MenuItem("新建");
miOpen= new MenuItem("打开");
miSave= new MenuItem("保存");
miSaveAs= new MenuItem("另存为");
miExit= new MenuItem("退出");
miExit.addActionListener(this); //为退出菜单添加监听
* 添加上面创建的子菜单到文件菜单下
mnFile.add(miNew);
mnFile.add(miOpen);
mnFile.add(miSave);
mnFile.add(miSaveAs);
mnFile.addSeparator(); //将一个分隔线或连字符添加到菜单的当前位置
mnFile.add(miExit);
miBinary= new CheckboxMenuItem("二进制"); //创建在复选框的子菜单
miFont= new MenuItem("字体"); //创建子菜单
* 添加miBinary、miFont两个子菜单到mnFormat（格式）下
mnFormat.add(miBinary);
mnFormat.add(miFont);
mb.add(mnFile);
mb.add(mnEdit);
mb.add(mnFormat);
mb.add(mnHelp);
setMenuBar(mb); //添加菜单栏到Frame
* 关闭窗口时,关闭运行成语
System.exit(0);
public static void main(String args[]){
TestMenu tm=new TestMenu();
tm.setVisible(true); //设置显示窗体,true为显示,false为隐藏
/**
* 监听事件,实现ActionListener接口的actionPerformed方法
*/
String s = e.getActionCommand(); //获取选中菜单的名称
System.out.println(s);
if(s.equals("退出")){
System.exit(0); //停止运行程序
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