学生管理系统
https://blog.csdn.net/howard2005/article/details/79336373
计算器 ：https://blog.csdn.net/without_scruple/article/details/78603605
https://blog.csdn.net/CCSUXWZ/article/details/78239089
枚举 ： https://blog.csdn.net/qq_27093465/article/details/52180865
public class lei {
public static void main(String[] args) {
// TODO Auto-generated method stub
String s1 = "abc";
String s2 = new String ("abc");
System.out.println(s1);
System.out.println(s2);//s1有一个对象 s2有两个对象
System.out.println(s1==s2);//false
System.out.println(s1.equals(s2));//true
}
}
2.排序
https://www.cnblogs.com/onepixel/articles/7674659.html
3.创建一个文件
String dirname = "C:\\a";
File d = new File(dirname);
// 现在创建目录
d.mkdirs();
4.文档的输入输出
import java.io.*;
public class iodemo {
public static void main(String args[]) {
try {
byte bWrite[] = { 11, 21, 3, 40, 5 };
OutputStream os = new FileOutputStream("test.txt");
for (int x = 0; x < bWrite.length; x++) {
os.write(bWrite[x]); // writes the bytes
}
os.close();
InputStream is = new FileInputStream("test.txt");
int size = is.available();
for (int i = 0; i < size; i++) {
System.out.print((char) is.read() + " ");
}
is.close();
} catch (IOException e) {
System.out.print("Exception");
}
}
}
5.读取目录
一个目录其实就是一个 File 对象，它包含其他文件和文件夹。
如果创建一个 File 对象并且它是一个目录，那么调用 isDirectory() 方法会返回 true。
可以通过调用该对象上的 list() 方法，来提取它包含的文件和文件夹的列表。
下面展示的例子说明如何使用 list() 方法来检查一个文件夹中包含的内容：
import java.io.File;
public class iodemo{
public static void main(String args[]) {
String dirname = "C:\\a";
File f1 = new File(dirname);
if(f1.isDirectory())
{
System.out.println("目录："+dirname);
String b[] = f1.list();
for(int x=0;ximport java.awt.*;
public class iodemo
{
public static void main(String args[])
{
Frame f = new Frame("my frame");
f.setSize(200,200);
f.setLocation(300, 200);
f.setVisible(true);
f.setLayout(new FlowLayout());
Button btn = new Button ("我是一个按键");
f.add(btn);
}
}
- 学生管理系统
import java.util.*;
class Stu {
private String stuNum;//学号
private String name;//姓名
private String gender;//性别
private int age;//年龄
private int score;//分数
public Stu() {
super();
}
public String getStuNum() {
return stuNum;
}
public void setStuNum(String stuNum) {
this.stuNum = stuNum;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public int getScore() {
return score;
}
public void setScore(int score) {
this.score = score;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
public class iodemo {
static Stu[] Stu=new Stu[100];//定义学生数组，容量为100
static int number=0;
static Scanner scanner=new Scanner(System.in);
public static void main(String args[]){
int choice;
System.out.println("这是一个学生信息管理系统，最大容量为100，欢迎您对本系统的使用");
while(true){
System.out.println("1.信息添加");
System.out.println("2.信息查看");
System.out.println("3.信息修改");
System.out.println("4.信息删除");
System.out.println("5.信息按成绩从低到高排序");
System.out.println("6.信息查询");
System.out.println("7.退出");
System.out.println("请输入你要进行的操作");
choice=scanner.nextInt();
if(choice==7)break;
switch(choice){
case 1: add(); break;//添加学生信息
case 2: show();break;//查询学生信息
case 3: change();break;//修改学生信息
case 4: delete();break;//删除学生信息
case 5: paixu();break;//对学生信息排序
case 6: query();break;//查询学生信息
}
}
System.out.println("感谢您对本系统的使用，欢迎下次继续使用");
}
static void add(){//添加学生信息
while(true){
System.out.println("点击任意键继续添加学生信息，停止添加输入0");
if(scanner.nextInt()==0)break;
System.out.println("请输入该学生的学号，姓名，性别，年龄，成绩");
Stu[number]=new Stu();
Stu[number].setStuNum(scanner.next());
Stu[number].setName(scanner.next());
Stu[number].setGender(scanner.next());
Stu[number].setAge(scanner.nextInt());
Stu[number].setScore(scanner.nextInt());
number++;
System.out.println("添加成功");
}
}
static void show(){//展示学生信息
System.out.println("*******************************************");
System.out.println(" 学号 姓名 性别 年龄 成绩");
for(int i=0;iStu[j].getScore())
{temp=Stu[i];Stu[i]=Stu[j];Stu[j]=temp;}
}
System.out.println("排序完成，选择”学生信息查看“进行查看");
}
static void change(){//改变学生信息
System.out.println("请输入要修改信息的学生学号");
String Stunumber=scanner.next();
for(int i=0;i 8.读取文本
（可以读汉字）
File file = new File("C:\\a.txt");
BufferedReader reader = new BufferedReader(new FileReader(file));
// 构建InputStreamReader对象,编码与写入相同
StringBuffer sb = new StringBuffer();
while (reader.ready()) {
sb.append(reader.readLine());
// 转成char加到StringBuffer对象中
sb.append("\r\n");
}
System.out.println(sb.toString());
reader.close();
（不能读汉字）
InputStream is = new FileInputStream("C:\\a.txt") ;
int size = is.available();
for (int i = 0; i < size; i++) {
System.out.print( is.read() + " ");
}
is.close();
(某种情况可以)
File f = new File("C:\\a.txt");
FileInputStream fip = new FileInputStream(f);
// 构建FileInputStream对象
InputStreamReader reader = new InputStreamReader(fip, "UTF-8");
// 构建InputStreamReader对象,编码与写入相同
StringBuffer sb = new StringBuffer();
while (reader.ready()) {
sb.append((char) reader.read());
// 转成char加到StringBuffer对象中
}
System.out.println(sb.toString());
reader.close();
// 关闭读取流
fip.close();
// 关闭输入流,释放系统资源
7.打开与保存
import java.awt.*;
import java.awt.event.*;
import java.io.*;
class guidemo
{
private Frame f;
private TextArea ta;
private MenuBar menuBar;
private Menu menu;
private MenuItem openItem,saveItem;
private FileDialog openDialog,saveDialog;
private File file;
public guidemo()
{
init();
}
public void init()
{
f = new Frame("myFrame");
f.setBounds(300,200,500,400);
ta = new TextArea();
openDialog = new FileDialog(f,"mydialog",FileDialog.LOAD);
saveDialog = new FileDialog(f,"mydialog",FileDialog.SAVE);
menuBar = new MenuBar();
menu = new Menu("菜单");
openItem = new MenuItem("打开");
saveItem = new MenuItem("保存");
menu.add(openItem);
menu.add(saveItem);
menuBar.add(menu);
f.setMenuBar(menuBar);
f.add(ta);
myEvent();
f.setVisible(true);
}
public void myEvent()
{
f.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});
openItem.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
openDialog.setVisible(true);
String fileName = openDialog.getFile();
String directionName = openDialog.getDirectory();
if(fileName == null || directionName == null)
return ;
ta.setText("");
file = new File(directionName,fileName);
try {
BufferedReader buff = new BufferedReader(new FileReader(file));
String line = null;
while((line=buff.readLine())!=null)
{
ta.append(line+"\r\n");
}
buff.close();
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
});
saveItem.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
if(file==null)
{
saveDialog.setVisible(true);
String fileName = saveDialog.getFile();
String directionName = saveDialog.getDirectory();
if(fileName == null || directionName == null)
return ;
file = new File(directionName,fileName);
}
try {
BufferedWriter bwr = new BufferedWriter(new FileWriter(file));
String text = ta.getText();
bwr.write(text);
bwr.flush();
bwr.close();
} catch (FileNotFoundException e2) {
// TODO Auto-generated catch block
e2.printStackTrace();
} catch (IOException e2) {
// TODO Auto-generated catch block
e2.printStackTrace();
}
}
});
}
}
public class gui {
public static void main(String []args)
{
new guidemo();
}
}
8.LineNumberReader的用法
同BufferedReader相似，但又有getLineNumber和setLineNumber方法
image.png
9.UDP通信
import java.io.*;
import java.net.*;
class Sender implements Runnable
{
public void run()
{
try {
DatagramSocket ds = new DatagramSocket();
BufferedReader buf = new BufferedReader(new InputStreamReader(System.in));
String line = null;
DatagramPacket dp = null;
do {
line = buf.readLine();
byte []by = line.getBytes();
dp = new DatagramPacket(by,by.length,InetAddress.getByName("127.0.0.1"),8090);
ds.send(dp);
}while(!line.equals("exit"));
ds.close();
}catch(IOException e)
{
e.printStackTrace();
}
}
}
class Receiver implements Runnable
{
public void run()
{
try {
DatagramSocket ds = new DatagramSocket(8090);
byte []by = new byte[1024];
DatagramPacket dp = new DatagramPacket(by,by.length);
String line = null;
do {
ds.receive(dp);
line = new String (dp.getData(),0,dp.getLength());
System.out.println(line);
}while(!line.equals("exit"));
ds.close();
}catch(IOException e)
{
e.printStackTrace();
}
}
}
public class test{
public static void main(String []args)
{
new Thread(new Sender()).start();
new Thread(new Receiver()).start();
}
}
10.TCP 上传文件
import java.net.*;
import java.io.*;
public class demo{
public static void main(String []args) throws Exception
{
Socket s = new Socket("192.168.56.1",8092);
BufferedReader bufr =
new BufferedReader(new FileReader("test.java"));
PrintWriter pw = new PrintWriter(s.getOutputStream(),true);
BufferedReader bufin =
new BufferedReader(new InputStreamReader(s.getInputStream()));
String line = null;
while((line=bufr.readLine())!=null)
{
pw.println(line);
}
s.shutdownOutput();
String str = bufin.readLine();
System.out.println(str);
bufr.close();
s.close();
}
}
import java.net.*;
import java.io.*;
public class send {
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
ServerSocket ss = new ServerSocket(8092);
Socket s = ss.accept();
String ip = s.getInetAddress().getHostAddress();
System.out.println(ip+" is connect");
BufferedReader bufr =
new BufferedReader(new InputStreamReader(s.getInputStream()));
PrintWriter out = new PrintWriter(new FileWriter("a.txt"),true);
String line = null;
while((line=bufr.readLine())!=null)
{
out.println(line);
}
PrintWriter pw = new PrintWriter(s.getOutputStream(),true);
pw.println("上传完成");
out.close();
s.close();
ss.close();
}
}
11.布局
import java.awt.*;
public class buttonDir{
public static void main(String args[]){
Frame f = new Frame("BorderLayout");
f.setLayout(new BorderLayout());
f.add("North", new Button("North"); //一个很好的输入方法
//第一个参数表示把按钮添加到容器的North区域
f.add("South", new Button("South");
//第一个参数表示把按钮添加到容器的South区域
f.add("East", new Button("East");
//第一个参数表示把按钮添加到容器的East区域
f.add("West", new Button("West");
//第一个参数表示把按钮添加到容器的West区域
f.add("Center", new Button("Center");
//第一个参数表示把按钮添加到容器的Center区域
f.setSize(200,200);
f.setVisible(true);
}
}