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一楼的说的够全面了,不过稍有误解.
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再来表示抱歉,我对编程语言中的中文名词非常不了解,所以如果以下的回复对你的阅读或者理解造成困难,请见谅.
1.首先,要明白这个问题的答案,需要了解call (pass) by value 和 call (pass) by reference 的区别.简单来说:
call by value通常是复制这个parameter的值去另外一块内存里,然后传给function, 所以在method/function里边对这个变量的所有变更,实际上都是对复制过来的镜像进行操作,不会对原本的variable有任何影响.
call by reference是将parameter的reference传给function,简单点理解就是直接把variable传给function.所以说这个variable的值是可以被function改变的.这个用法在c/c++中非常常见,用法是variable_name.
2.再来,在Java里边,你可以很简单的理解为: Java中只有call by value, 也就是说,所以所有传给function的parameter本身都不会被改变. (这是最简单直白的理解,当然也有另一种常从sun的人那边听到的说法:Java是call by value + call by reference by value)
3.那么现在的问题就是为什么第二个结果是2了. 首先说一下sun官方的解释: 对于reference type在作为parameter/argument的时候,也是call by value, 但是在你拥有足够权限时(比方说那个变量是public的, 不是final的等等各种符合的情况),可以修改这个object中fields的值(也就是属于这个object(严谨点讲是an instance of the object) 内部的变量, 在你的例子中, ko 里边的 a 就是一个field, 所以update(ko)会使ko.a变成2).
4.如果你是一个有过c/c++学习经验的人或者你以上的解释很难理解,以下这种说法或许更适合你 (当然了,这只是大多包括我在内有c经验的人的一种理解方式)
这里可以引入一个新的概念,pointer. 这是一种比较特殊的变量,它内部所储存的东西,其实只是另外一个变量的内存地址. 如果对内存没有概念,你可以把它简单理解为是风筝的线轴,虽然看它本身看不出什么端倪,但是顺着摸过去总会找到风筝,看到它是什么样子. 以pointer方式理解Java的人,通常会说: Type variable = new Type(); 这个过程中,最后生成的这个variable其实就是一个pointer,而不是instance本身.
在Java中, 有c/c++经验的人通常认为Java是call by value.同时,当一个变量用在储存reference type的时候,实际上储存的是它的pointer,这也一样可以解释为什么ko.a会有2这个结果,因为虽然pointer被传到function里边时,本身是call by value,无法被改变.但这并不影响function本身对这个pointer指向的object的内容做任何改变. 当然,再次声明,这只是一种帮助有c/c++经验的人理解的方法. Sun本身严正声明Java里边没有pointer这个东西的存在.
5. 再来解释一下为什么说楼上所说的(或者说楼上引用的)理解略有偏差.
引用"我们上面刚学习了JAVA的数据类型，则有：值类型就是按值传递的，而引用类型是按引用传递的" 这句话很明显的有两点错误. 第一点,如果我上面所说的,Java是没有call by reference的.
第二点,暂且假设Java里边是有call by reference的, 这句话依然不成立.
Java中的变量有两种类型: primitive types 和 reference type.
primitive type包括byte, short, int, long, char, boolean, float和double.
而这8种之外的所有的,都是reference type.
下面是一段对你的贴上来的code的一点延伸,希望可以帮助你更好的理解Java中的argument / parameter到底是如何运作的.
public class Test {
public static void main(String[] args) {
int a = 1;
Koo koo = new Koo();
Object o = new Integer(1);
Koo newKoo = new Koo();
update(a);
update(koo);
update(o);
update(newKoo);
newUpdate(newKoo);
System.out.println(a);
System.out.println(koo.a);
System.out.println(o);
System.out.println(newKoo.a);
}
static void update(int a) {
a++;
}
static void update(Koo koo) {
koo.a++;
}
static void update(Object o) {
o = (int) (Integer.parseInt(o.toString()) + 1);
}
static void newUpdate(Koo koo) {
koo = new Koo();
}
}
class Koo {
int a = 1;
}
/*
o = (int) (Integer.parseInt(o.toString()) + 1); 这一行中的(int)纯粹是多余的,是否有这个casting对code本身没有任何影响. 如果你高兴也可以用
o = new Integer(Integer.parseInt(o.toString()) + 1);
或者干脆
o = Integer.parseInt(o.toString()) + 1;
*/
以上这些code运行之后会得到1 2 1 2的结果. 后面两个结果可以很好的说明, 即使对objects (reference type variables) 来看, Java所应用的也并不是call by reference. 否则的话,以上code运行结果应该是1 2 2 1
希望你可以真正理解这个新的例子中,产生1212这个结果的原因,从而对Java中的arguments有一个系统全面的认识.
图片是相关资料的链接,知道里貌似不能加网址
给你一个俄罗斯方块的把！！
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.*;
import javax.swing.Timer;
public class Tetris extends JFrame {
public Tetris() {
Tetrisblok a = new Tetrisblok();
addKeyListener(a);
add(a);
}
public static void main(String[] args) {
Tetris frame = new Tetris();
JMenuBar menu = new JMenuBar();
frame.setJMenuBar(menu);
JMenu game = new JMenu("游戏");
JMenuItem newgame = game.add("新游戏");
JMenuItem pause = game.add("暂停");
JMenuItem goon = game.add("继续");
JMenuItem exit = game.add("退出");
JMenu help = new JMenu("帮助");
JMenuItem about = help.add("关于");
menu.add(game);
menu.add(help);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(220, 275);
frame.setTitle("Tetris内测版");
// frame.setUndecorated(true);
frame.setVisible(true);
frame.setResizable(false);
}
}
// 创建一个俄罗斯方块类
class Tetrisblok extends JPanel implements KeyListener {
// blockType 代表方块类型
// turnState代表方块状态
private int blockType;
private int score = 0;
private int turnState;
private int x;
private int y;
private int i = 0;
int j = 0;
int flag = 0;
// 定义已经放下的方块x=0-11,y=0-21;
int[][] map = new int[13][23];
// 方块的形状 第一组代表方块类型有S、Z、L、J、I、O、T 7种 第二组 代表旋转几次 第三四组为 方块矩阵
private final int shapes[][][] = new int[][][] {
// i
{ { 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0 },
{ 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0 } },
// s
{ { 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0 },
{ 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0 } },
// z
{ { 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0 } },
// j
{ { 0, 1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0 },
{ 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 } },
// o
{ { 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 } },
// l
{ { 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0 },
{ 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 } },
// t
{ { 0, 1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 0, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0 } } };
// 生成新方块的方法
public void newblock() {
blockType = (int) (Math.random() * 1000) % 7;
turnState = (int) (Math.random() * 1000) % 4;
x = 4;
y = 0;
if (gameover(x, y) == 1) {
newmap();
drawwall();
score = 0;
JOptionPane.showMessageDialog(null, "GAME OVER");
}
}
// 画围墙
public void drawwall() {
for (i = 0; i 12; i++) {
map[i][21] = 2;
}
for (j = 0; j 22; j++) {
map[11][j] = 2;
map[0][j] = 2;
}
}
// 初始化地图
public void newmap() {
for (i = 0; i 12; i++) {
for (j = 0; j 22; j++) {
map[i][j] = 0;
}
}
}
// 初始化构造方法
Tetrisblok() {
newblock();
newmap();
drawwall();
Timer timer = new Timer(1000, new TimerListener());
timer.start();
}
// 旋转的方法
public void turn() {
int tempturnState = turnState;
turnState = (turnState + 1) % 4;
if (blow(x, y, blockType, turnState) == 1) {
}
if (blow(x, y, blockType, turnState) == 0) {
turnState = tempturnState;
}
repaint();
}
// 左移的方法
public void left() {
if (blow(x - 1, y, blockType, turnState) == 1) {
x = x - 1;
}
;
repaint();
}
// 右移的方法
public void right() {
if (blow(x + 1, y, blockType, turnState) == 1) {
x = x + 1;
}
;
repaint();
}
// 下落的方法
public void down() {
if (blow(x, y + 1, blockType, turnState) == 1) {
y = y + 1;
delline();
}
;
if (blow(x, y + 1, blockType, turnState) == 0) {
add(x, y, blockType, turnState);
newblock();
delline();
}
;
repaint();
}
// 是否合法的方法
public int blow(int x, int y, int blockType, int turnState) {
for (int a = 0; a 4; a++) {
for (int b = 0; b 4; b++) {
if (((shapes[blockType][turnState][a * 4 + b] == 1) (map[x
+ b + 1][y + a] == 1))
|| ((shapes[blockType][turnState][a * 4 + b] == 1) (map[x
+ b + 1][y + a] == 2))) {
return 0;
}
}
}
return 1;
}
// 消行的方法
public void delline() {
int c = 0;
for (int b = 0; b 22; b++) {
for (int a = 0; a 12; a++) {
if (map[a][b] == 1) {
c = c + 1;
if (c == 10) {
score += 10;
for (int d = b; d 0; d--) {
for (int e = 0; e 11; e++) {
map[e][d] = map[e][d - 1];
}
}
}
}
}
c = 0;
}
}
// 判断你挂的方法
public int gameover(int x, int y) {
if (blow(x, y, blockType, turnState) == 0) {
return 1;
}
return 0;
}
// 把当前添加map
public void add(int x, int y, int blockType, int turnState) {
int j = 0;
for (int a = 0; a 4; a++) {
for (int b = 0; b 4; b++) {
if (map[x + b + 1][y + a] == 0) {
map[x + b + 1][y + a] = shapes[blockType][turnState][j];
}
;
j++;
}
}
}
// 画方块的的方法
public void paintComponent(Graphics g) {
super.paintComponent(g);
// 画当前方块
for (j = 0; j 16; j++) {
if (shapes[blockType][turnState][j] == 1) {
g.fillRect((j % 4 + x + 1) * 10, (j / 4 + y) * 10, 10, 10);
}
}
// 画已经固定的方块
for (j = 0; j 22; j++) {
for (i = 0; i 12; i++) {
if (map[i][j] == 1) {
g.fillRect(i * 10, j * 10, 10, 10);
}
if (map[i][j] == 2) {
g.drawRect(i * 10, j * 10, 10, 10);
}
}
}
g.drawString("score=" + score, 125, 10);
g.drawString("抵制不良游戏，", 125, 50);
g.drawString("拒绝盗版游戏。", 125, 70);
g.drawString("注意自我保护，", 125, 90);
g.drawString("谨防受骗上当。", 125, 110);
g.drawString("适度游戏益脑，", 125, 130);
g.drawString("沉迷游戏伤身。", 125, 150);
g.drawString("合理安排时间，", 125, 170);
g.drawString("享受健康生活。", 125, 190);
}
// 键盘监听
public void keyPressed(KeyEvent e) {
switch (e.getKeyCode()) {
case KeyEvent.VK_DOWN:
down();
break;
case KeyEvent.VK_UP:
turn();
break;
case KeyEvent.VK_RIGHT:
right();
break;
case KeyEvent.VK_LEFT:
left();
break;
}
}
// 无用
public void keyReleased(KeyEvent e) {
}
// 无用
public void keyTyped(KeyEvent e) {
}
// 定时器监听
class TimerListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
repaint();
if (blow(x, y + 1, blockType, turnState) == 1) {
y = y + 1;
delline();
}
;
if (blow(x, y + 1, blockType, turnState) == 0) {
if (flag == 1) {
add(x, y, blockType, turnState);
delline();
newblock();
flag = 0;
}
flag = 1;
}
;
}
}
}
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);
fDlg.setVisible(true);
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);
lFind.setBounds(10,30,80,20);
lReplace.setBounds(10,70,80,20);
tFind.setBounds(90,30,90,20);
tReplace.setBounds(90,70,90,20);
bFind.setBounds(190,30,80,20);
bReplace.setBounds(190,70,80,20);
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");
setSize(280,60);
setVisible(true);
}
public void showReplace(){
setTitle("查找替换");
setSize(280,110);
setVisible(true);
}
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 TextArea editor=new TextArea(); //可编辑的TextArea
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.addMenus(new String[]{"文件","编辑","查找","帮助"});
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"});
mb.addMenuItems(2,new String[]{"查找",null,"查找替换"});
mb.addMenuItems(3,new String[]{"我的记事本信息"});
add(editor); //为菜单项注册动作时间监听器
mb.addActionListener(this);
addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e){
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")){
try{
editor.setText(mf.getData());
}catch(IOException ie){}
}
else if(selected.equals("保存")){
try{
mf.setData(editor.getText());
}catch(IOException ie){}
}
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")){
cb.setData(editor.getSelectedText());
}
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")){
editor.replaceRange("",editor.getSelectionStart(),editor.getSelectionEnd());
}
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.setSize(650,450);
memo.setVisible(true);
}
}
第一种
package com.at.java;
class PIThread extends Thread{
public void run(){
double num=1,PI=0;int i=0;
while(num0.001) {
num=(double)4/(2*i+++1);
if(i%2==0)PI-=num;
else PI+=num;
System.out.println("派的数值为"+PI);
if(num=0.001)System.out.println("××××××××××派的数值计算已经结束××××××××××");
}
}
}
class EThread extends Thread{
public void run(){
double num=1,E=0;int i=1;
while(1/num0.00000001) {
num=num*i++;
E+=1/num;
System.out.println("自然对数E的数值为"+E);
if(1/num=0.00000001)System.out.println("××××××××××自然对数的数值计算已经结束××××××××××");
}
}
}
public class JustTest {
public static void main(String args[]) {
PIThread p=new PIThread();
EThread e=new EThread();
p.start();
e.start();
int sum=0;
for(int i=1;i1001;i++)
{
sum+=i;
System.out.println(sum);
}
System.out.println("×××××××××××××自动求和1到1000已经结束××××××××××××××××");
}
}
第二种
package com.at.java;
class PIThread implements Runnable{
public void run(){
double num=1,PI=0;int i=0;
while(num0.001) {
num=(double)4/(2*i+++1);
if(i%2==0)PI-=num;
else PI+=num;
System.out.println("派的数值为"+PI);
if(num=0.001)System.out.println("××××××××××派的数值计算已经结束××××××××××");
}
}
}
class EThread implements Runnable{
public void run(){
double num=1,E=0;int i=1;
while(1/num0.00000001) {
num=num*i++;
E+=1/num;
System.out.println("自然对数E的数值为"+E);
if(1/num=0.00000001)System.out.println("××××××××××自然对数的数值计算已经结束××××××××××");
}
}
}
public class JustTest {
public static void main(String args[]) {
PIThread p=new PIThread();
EThread e=new EThread();
Thread t1=new Thread(p);
Thread t2=new Thread(e);
t1.start();
t2.start();
int sum=0;
for(int i=1;i1001;i++)
{
sum+=i;
System.out.println(sum);
}
System.out.println("×××××××××××××自动求和1到1000已经结束××××××××××××××××");
}
}
都已经验证过，正常运行
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
class test implements ActionListener
{
JFrame frame;
JButton b1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,b12,b13,b14,b15,b16,b17,b18,b19,b20,b21,b22,b23,b24,b25,b26,b27,b28,b29,b30,b31;
JTextArea ta;
JPanel p1,p2,p3,p4;
JMenuBar mb;
JMenu m1,m2,m3;
JMenuItem mt1,mt2,mt3,mt4,mt5,mt6,mt7;
JRadioButton rb1,rb2;
ButtonGroup bg;
Double d1=0.0,d2=0.0,d3=0.0,d4=1.0,d5=1.0;
String s1="",s2="",s3="",s4="";
int a=0;
char c1;
int i=0;
public static void main(String[] args)
{
test that=new test();
that.go();
}
public void go()
{
frame=new JFrame("计算器");
Container cp= frame.getContentPane();
cp.setLayout(new FlowLayout());
b1=new JButton("7");b2=new JButton("8");b3=new JButton("9");b4=new JButton("/");b5=new JButton("1/x");b6=new JButton("sin");b7=new JButton("log");
b8=new JButton("4");b9=new JButton("5");b10=new JButton("6");b11=new JButton("*");b12=new JButton("x^y");b13=new JButton("cos");b14=new JButton("ln");
b15=new JButton("1");b16=new JButton("2");b17=new JButton("3");b18=new JButton("-");b19=new JButton(new ImageIcon("lanying.gif"));b20=new JButton("tan");b21=new JButton("x^3");
b22=new JButton("0");b23=new JButton("+/-");b24=new JButton(".");b25=new JButton("+");b26=new JButton("√x");b27=new JButton("cot");b28=new JButton("x^2");
b29=new JButton("Backspace");b30=new JButton("C");b31=new JButton("=");
mb=new JMenuBar();
m1=new JMenu("文件(F)");m2=new JMenu("编辑(E)");m3=new JMenu("帮助(H)");
mt1=new JMenuItem("清零");mt2=new JMenuItem("退出");mt3=new JMenuItem("复制");mt4=new JMenuItem("粘贴");mt5=new JMenuItem("版本");mt6=new JMenuItem("标准型");mt7=new JMenuItem("科学型");
ta=new JTextArea(1,30);
p1=new JPanel();p2=new JPanel();p3=new JPanel();p4=new JPanel();
rb1=new JRadioButton("科学型");rb2=new JRadioButton("标准型");
bg=new ButtonGroup();
b1.setForeground(Color.blue);b1.setBackground(Color.white);b2.setForeground(Color.blue);b2.setBackground(Color.white);
b3.setForeground(Color.blue);b3.setBackground(Color.white);b8.setForeground(Color.blue);b8.setBackground(Color.white);
b9.setForeground(Color.blue);b9.setBackground(Color.white);b10.setForeground(Color.blue);b10.setBackground(Color.white);
b15.setForeground(Color.blue);b15.setBackground(Color.white);b16.setForeground(Color.blue);b16.setBackground(Color.white);
b17.setForeground(Color.blue);b17.setBackground(Color.white);b22.setForeground(Color.blue);b22.setBackground(Color.white);
b23.setForeground(Color.blue);b23.setBackground(Color.white);b24.setForeground(Color.blue);b24.setBackground(Color.white);
b4.setForeground(Color.red);b4.setBackground(Color.white);b11.setForeground(Color.red);b11.setBackground(Color.white);
b18.setForeground(Color.red);b18.setBackground(Color.white);b25.setForeground(Color.red);b25.setBackground(Color.white);
b5.setForeground(Color.blue);b5.setBackground(Color.white);b6.setForeground(Color.blue);b6.setBackground(Color.white);
b7.setForeground(Color.blue);b7.setBackground(Color.white);b12.setForeground(Color.blue);b12.setBackground(Color.white);
b13.setForeground(Color.blue);b13.setBackground(Color.white);b14.setForeground(Color.blue);b14.setBackground(Color.white);
b19.setForeground(Color.blue);b19.setBackground(Color.white);b20.setForeground(Color.blue);b20.setBackground(Color.white);
b21.setForeground(Color.blue);b21.setBackground(Color.white);b26.setForeground(Color.blue);b26.setBackground(Color.white);
b27.setForeground(Color.blue);b27.setBackground(Color.white);b28.setForeground(Color.blue);b28.setBackground(Color.white);
b29.setForeground(Color.red);b29.setBackground(Color.white);b30.setForeground(Color.red);b30.setBackground(Color.white);
b31.setForeground(Color.red);b31.setBackground(Color.white);
bg.add(rb1);bg.add(rb2);
p1.setBackground(Color.yellow);
cp.setBackground(Color.CYAN);
m1.setMnemonic(KeyEvent.VK_F);m2.setMnemonic(KeyEvent.VK_E);m3.setMnemonic(KeyEvent.VK_H);
m1.add(mt6);m1.add(mt7);m1.addSeparator();m1.add(mt1);m1.addSeparator();m1.add(mt2);m2.add(mt3);m2.addSeparator();m2.add(mt4);m3.add(mt5);
mb.add(m1);mb.add(m2);mb.add(m3);
frame.setJMenuBar(mb);
p2.setLayout(new GridLayout(4,7));
p3.setLayout(new GridLayout(1,3));
ta.setEditable(false);
p1.add(ta);
p2.add(b1);p2.add(b2);p2.add(b3);p2.add(b4);p2.add(b5);p2.add(b6);p2.add(b7);
p2.add(b8);p2.add(b9);p2.add(b10);p2.add(b11);p2.add(b12);p2.add(b13);p2.add(b14);
p2.add(b15);p2.add(b16);p2.add(b17);p2.add(b18);p2.add(b19);p2.add(b20);p2.add(b21);
p2.add(b22);p2.add(b23);p2.add(b24);p2.add(b25);p2.add(b26);p2.add(b27);p2.add(b28);
p3.add(b29);p3.add(b30);p3.add(b31);
Border etched=BorderFactory.createEtchedBorder();
Border border=BorderFactory.createTitledBorder(etched,"计算类型");
p4.add(rb1);p4.add(rb2);
p4.setBorder(border);
b2.setActionCommand("8");
b2.addActionListener(this);
cp.add(p1);cp.add(p4);cp.add(p2);cp.add(p3);
frame.setSize(400,330);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
b1.setActionCommand("7");
b1.addActionListener(this);
b2.setActionCommand("8");
b2.addActionListener(this);
b3.setActionCommand("9");
b3.addActionListener(this);
b4.setActionCommand("/");
b4.addActionListener(this);
b5.setActionCommand("1/x");
b5.addActionListener(this);
b6.setActionCommand("sin");
b6.addActionListener(this);
b7.setActionCommand("log");
b7.addActionListener(this);
b8.setActionCommand("4");
b8.addActionListener(this);
b9.setActionCommand("5");
b9.addActionListener(this);
b10.setActionCommand("6");
b10.addActionListener(this);
b11.setActionCommand("*");
b11.addActionListener(this);
b12.setActionCommand("x^y");
b12.addActionListener(this);
b13.setActionCommand("cos");
b13.addActionListener(this);
b14.setActionCommand("ln");
b14.addActionListener(this);
b15.setActionCommand("1");
b15.addActionListener(this);
b16.setActionCommand("2");
b16.addActionListener(this);
b17.setActionCommand("3");
b17.addActionListener(this);
b18.setActionCommand("-");
b18.addActionListener(this);
b19.setActionCommand("x!");
b19.addActionListener(this);
b20.setActionCommand("tan");
b20.addActionListener(this);
b21.setActionCommand("x^3");
b21.addActionListener(this);
b22.setActionCommand("0");
b22.addActionListener(this);
b23.setActionCommand("+/-");
b23.addActionListener(this);
b24.setActionCommand(".");
b24.addActionListener(this);
b25.setActionCommand("+");
b25.addActionListener(this);
b26.setActionCommand("√x");
b26.addActionListener(this);
b27.setActionCommand("cot");
b27.addActionListener(this);
b28.setActionCommand("x^2");
b28.addActionListener(this);
b29.setActionCommand("Backspace");
b29.addActionListener(this);
b30.setActionCommand("C");
b30.addActionListener(this);
b31.setActionCommand("=");
b31.addActionListener(this);
rb1.setActionCommand("kxx");
rb1.addActionListener(this);
rb2.setActionCommand("bzx");
rb2.addActionListener(this);
}
public void actionPerformed(ActionEvent e) //throws Exception
{
if (e.getActionCommand()=="bzx")
{
b5.setEnabled(false);b6.setEnabled(false);b7.setEnabled(false);
b12.setEnabled(false);b13.setEnabled(false);b14.setEnabled(false);
b19.setEnabled(false);b20.setEnabled(false);b21.setEnabled(false);
b26.setEnabled(false);b27.setEnabled(false);b28.setEnabled(false);
}
if (e.getActionCommand()=="kxx")
{
b5.setEnabled(true);b6.setEnabled(true);b7.setEnabled(true);
b12.setEnabled(true);b13.setEnabled(true);b14.setEnabled(true);
b19.setEnabled(true);b20.setEnabled(true);b21.setEnabled(true);
b26.setEnabled(true);b27.setEnabled(true);b28.setEnabled(true);
}
if (e.getActionCommand()=="1")
{
ta.append("1");
}
if (e.getActionCommand()=="2")
{
ta.append("2");
}
if (e.getActionCommand()=="3")
{
ta.append("3");
}
if (e.getActionCommand()=="4")
{
ta.append("4");
}
if (e.getActionCommand()=="5")
{
ta.append("5");
}
if (e.getActionCommand()=="6")
{
ta.append("6");
}
if (e.getActionCommand()=="7")
{
ta.append("7");
}
if (e.getActionCommand()=="8")
{
ta.append("8");
}
if (e.getActionCommand()=="9")
{
ta.append("9");
}
if (e.getActionCommand()=="0")
{
ta.append("0");
}
if (e.getActionCommand()=="+")
{
s1=ta.getText();
d1 = Double.parseDouble(s1);
ta.setText("");
i=1;
}
if (e.getActionCommand()=="-")
{
s1=ta.getText();
d1 = Double.parseDouble(s1);
ta.setText("");
i=2;
}
if (e.getActionCommand()=="*")
{
s1=ta.getText();
d1 = Double.parseDouble(s1);
ta.setText("");
i=3;
}
if (e.getActionCommand()=="/")
{
s1=ta.getText();
d1 = Double.parseDouble(s1);
ta.setText("");
i=4;
}
if (e.getActionCommand()=="=")
{
s2=ta.getText();
d2=Double.parseDouble(s2);
if(i==1)
{
d3=d1+d2;
ta.setText( d3.toString());
}
if(i==2)
{
d3=d1-d2;
ta.setText( d3.toString());
}
if(i==3)
{
d3=d1*d2;
ta.setText( d3.toString());
}
if(i==4)
{
if(d2==0.0)
ta.setText("ERROR");
else
{
d3=d1/d2;
ta.setText( d3.toString());
}
}
if (i==5)
{
s2=ta.getText();
d2 = Double.parseDouble(s2);
for (int l=1;l=d2 ; l++)
{
d5=d5*d1;
}
ta.setText( d5.toString());
}
}
if (e.getActionCommand()=="C")
{
ta.setText("");
d4=1.0;
d5=1.0;
}
/*if (e.getActionCommand()=="Backspace")
{
s3=ta.getText();
a=s3.length();
//ta.cut(ta.select(a-1,a));
s4=ta.getText(1,3);
ta.setText(s4);
}
*/
if (e.getActionCommand()=="1/x")
{
s1=ta.getText();
d1 = Double.parseDouble(s1);
d2=1/d1;
ta.setText( d2.toString());
}
if (e.getActionCommand()==".")
{
ta.append(".");
}
if (e.getActionCommand()=="+/-")
{
s1=ta.getText();
d1 = Double.parseDouble(s1);
d2=0-d1;
ta.setText( d2.toString());
}
if (e.getActionCommand()=="x^2")
{
s1=ta.getText();
d1 = Double.parseDouble(s1);
d2=d1*d1;
ta.setText( d2.toString());
}
if (e.getActionCommand()=="x^3")
{
s1=ta.getText();
d1 = Double.parseDouble(s1);
d2=d1*d1*d1;
ta.setText( d2.toString());
}
if (e.getActionCommand()=="x^y")
{
s1=ta.getText();
d1 = Double.parseDouble(s1);
ta.setText("");
i=5;
// d2=d1*d1*d1;
// ta.setText( d2.toString());
}
if (e.getActionCommand()=="√x")
{
s1=ta.getText();
d1 = Double.parseDouble(s1);
d2=Math.sqrt(d1);
ta.setText( d2.toString());
}
if (e.getActionCommand()=="x!")
{
s1=ta.getText();
d1 = Double.parseDouble(s1);
if (d10)
{
ta.setText( "error");
}
else if (d1==0)
{
ta.setText( "0.0");
}
else {
for (int k=1;k=d1 ;k++ )
d4=d4*k;
ta.setText( d4.toString());
}
}
if (e.getActionCommand()=="sin")
{
s1=ta.getText();
d1 = Double.parseDouble(s1);
d2=Math.sin(3.1415926*d1/180);
ta.setText( d2.toString());
}
}
}
这个是我以前写着玩的一个例子，可以运行起来看看，有保存，撤销，复制，剪切功能，自己研究研究
package test;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
public class MyNote {
private JFrame frame = new JFrame("记事本");
private JTextArea text = new JTextArea();
private static boolean flag = false; // 判断是否保存
public MyNote() {
JMenuBar bar = new JMenuBar();
JMenu edit = new JMenu("check");
JMenu check = new JMenu("edit");
JMenu help = new JMenu("help");
JMenuItem term = new JMenuItem("copy");
JMenuItem term1 = new JMenuItem("paste");
JMenuItem term2 = new JMenuItem("cut");
JMenuItem term3 = new JMenuItem("backout");
JMenuItem term4 = new JMenuItem("import");
JMenuItem term5 = new JMenuItem("open");
JMenuItem term6 = new JMenuItem("exit");
JMenuItem term7 = new JMenuItem("save to");
JMenuItem term8 = new JMenuItem("about");
JMenuItem term9 = new JMenuItem("save");
JMenuItem term10 = new JMenuItem("new");
Font font = new Font(null, JFrame.ABORT, 24);
text.setFont(font);
JScrollPane scroll = new JScrollPane(text);
frame.setJMenuBar(bar);
bar.add(edit);
bar.add(check);
bar.add(help);
edit.add(term7);
edit.add(term4);
edit.add(term5);
edit.add(term6);
check.add(term);
check.add(term1);
check.add(term2);
check.add(term3);
help.add(term8);
check.add(term9);
edit.add(term10);
frame.add(scroll);
text.setVisible(false);
frame.setSize(400, 400);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
frame.setLocation(500, 500);
// 事件注册
MenuListener m = new MenuListener();
term5.addActionListener(m);
NewListener n = new NewListener();
term4.addActionListener(n);
SaveListener s = new SaveListener();
term7.addActionListener(s);
CopyListener c = new CopyListener();
term.addActionListener(c);
PasteListener p = new PasteListener();
term1.addActionListener(p);
CutListener c1 = new CutListener();
term2.addActionListener(c1);
HelpListener h = new HelpListener();
term8.addActionListener(h);
ExitListener e = new ExitListener();
term6.addActionListener(e);
CloseListener c2 = new CloseListener();
frame.addWindowListener(c2);
BackOutListener b = new BackOutListener();
term3.addActionListener(b);
SaveActionListener s1 = new SaveActionListener();
term9.addActionListener(s1);
NewFileListener n1 = new NewFileListener();
term10.addActionListener(n1);
}
private class MenuListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
text.setVisible(true);
}
}
// 打开新文件
private class NewListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
text.setText("");
JFileChooser fileChooser = new JFileChooser();
int r = fileChooser.showOpenDialog(frame);
if (r == JFileChooser.APPROVE_OPTION) {
try {
File file = fileChooser.getSelectedFile();
FileReader fr = new FileReader(file);
char[] buf = new char[1024];
int len = 0;
while ((len = fr.read(buf)) != -1) {
text.append(new String(buf, 0, len));
}
fr.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
}
// 另存为
private class SaveListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
JFileChooser filechoose = new JFileChooser();
int r = filechoose.showSaveDialog(frame);
if (r == JFileChooser.APPROVE_OPTION) {
File file = filechoose.getSelectedFile();
try {
FileWriter writer = new FileWriter(file);
writer.write((String) text.getText());
writer.close();
// 下面方法也可以
/*
* PrintWriter print=new PrintWriter(file);
* print.write(text.getText()); print.close();
*/
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
}
// 复制
private class CopyListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
text.copy();
}
}
// 粘贴
private class PasteListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
text.paste();
}
}
// 剪切
private class CutListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
text.cut();
}
}
// 关于主题
private class HelpListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
JOptionPane.showMessageDialog(frame, "汪雄辉的无敌记事本");
}
}
private class ExitListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
JOptionPane.showMessageDialog(frame, "谢谢！");
try {
Thread.sleep(2000);
System.exit(0);
} catch (InterruptedException e1) {
e1.printStackTrace();
}
}
}
private class CloseListener implements WindowListener {
public void windowActivated(WindowEvent e) {
}
public void windowClosed(WindowEvent e) {
}
// 关闭窗口
public void windowClosing(WindowEvent e) {
StringBuffer sb = new StringBuffer();
try {
FileReader fr = new FileReader("未命名文件.txt");
char[] buf = new char[1024];
int len = 0;
while ((len = fr.read(buf)) != -1) {
sb.append(new String(buf, 0, len));
}
fr.close();
} catch (Exception e1) {
e1.getStackTrace();
}
String s = sb.toString();
if (flag == false || !(text.getText().equals(s))) {
int r = JOptionPane.showConfirmDialog(frame, "你还没有保存，要保存吗？");
if (r == JOptionPane.OK_OPTION) {
JFileChooser filechoose = new JFileChooser();
int r1 = filechoose.showSaveDialog(frame);
if (r1 == JFileChooser.APPROVE_OPTION) {
File file = filechoose.getSelectedFile();
try {
FileWriter writer = new FileWriter(file);
writer.write((String) text.getText());
writer.close();
System.exit(0);
// 下面方法也可以
/*
* PrintWriter print=new PrintWriter(file);
* print.write(text.getText()); print.close();
*/
} catch (IOException e1) {
e1.printStackTrace();
}
} else {
}
} else if (r == JOptionPane.NO_OPTION) {
System.exit(0);
} else {
}
} else
System.exit(0);
}
public void windowDeactivated(WindowEvent e) {
}
public void windowDeiconified(WindowEvent e) {
}
public void windowIconified(WindowEvent e) {
}
public void windowOpened(WindowEvent e) {
}
}
// 撤销
private class BackOutListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
if (flag == false)
text.setText("");
else {
try {
FileReader fr = new FileReader("未命名文件.txt");
char[] buf = new char[1024];
int len = 0;
while ((len = fr.read(buf)) != -1) {
text.setText(new String(buf, 0, len));
}
fr.close();
} catch (IOException e1) {
e1.getStackTrace();
}
}
}
}
// 保存文件
private class SaveActionListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
flag = true;
FileWriter writer;
try {
writer = new FileWriter("未命名文件.txt");
writer.write((String) text.getText());
writer.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
private class NewFileListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
new MyNote();
}
}
public static void main(String[] args) {
new MyNote();
}
}