必背的java代码 java必背知识点

给段最简单的java代码让我新手看一下

最简单的java代码肯定就是这个了，如下：

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public class MyFirstApp

{

public static void main(String[] args)

{

System.out.print("Hello world");

}

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急求JAVA源代码，小游戏或者别的

//这是个聊天程序，在ECLIPSE 运行 Client.java 就可以了。连接是：localhost

//Server 代码，

package message;

import java.io.*;

import java.net.*;

import java.util.*;

public class Server {

public static void main(String[] args) throws Exception{

System.out.print("Server");

ServerSocket socket=new ServerSocket(8888);

Vector v=new Vector();

while(true){

Socket sk=socket.accept();

DataInputStream in=new DataInputStream(sk.getInputStream());

DataOutputStream out=new DataOutputStream(sk.getOutputStream());

v.add(sk);

new ServerThread(in,v).start();

}

//ServerThread.java 代码

package message;

import java.net.*;

import java.io.*;

import java.util.*;

public class ServerThread extends Thread{

DataInputStream in;

Vector all;

public ServerThread(DataInputStream in,Vector v){

this.in=in;

this.all=v;

}

public void run()

{

while(true)

{

try{

String s1=in.readUTF();

for(int i=0;iall.size();i++)

{

Object obj=all.get(i);

Socket socket=(Socket)obj;

DataOutputStream out=new DataOutputStream(socket.getOutputStream());

out.writeUTF(s1);

System.out.print(i);

out.flush();

}

System.out.print("Message send over!");

}catch(Exception e){e.printStackTrace();};

}

//ClientFrame.java 代码

package message;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import java.net.*;

import java.io.*;

public class ClientFrame extends JFrame implements ActionListener{

JButton b1=new JButton ("SendMessage");

JButton b2=new JButton("Link Server");

JTextField t1=new JTextField(20);

JTextField t2=new JTextField(20);

JLabel l=new JLabel("输入服务器名字:");

JTextArea area=new JTextArea(10,20);

JPanel p1=new JPanel();

JPanel p2=new JPanel();

JPanel p3=new JPanel();

JPanel p4=new JPanel();

Socket socket;

public ClientFrame()

{

this.getContentPane().add(p1);

p2.add(new JScrollPane(area));

p3.add(t1);

p3.add(b1);

p4.add(l);

p4.add(t2);

p4.add(b2);

p2.setLayout(new FlowLayout());

p3.setLayout(new FlowLayout());

p4.setLayout(new FlowLayout());

p1.setLayout(new BorderLayout());

p1.add("North",p2);

p1.add("Center",p3);

p1.add("South",p4);

b1.addActionListener(this);

b2.addActionListener(this);

this.pack();

show();

}

public void actionPerformed(ActionEvent e)

{

if(e.getActionCommand().equals("Link Server"))

{

try{

socket=new Socket(t2.getText(),8888);

b2.setEnabled(false);

JOptionPane.showMessageDialog(this, "Connection Success");

DataInputStream in=new DataInputStream(socket.getInputStream());

new ClientThread(in,area).start();

}

catch(Exception e1){

JOptionPane.showMessageDialog(this, "Connection Error");

e1.printStackTrace();};

}

else if(e.getActionCommand().equals("SendMessage"))

{

try{

DataOutputStream out=new DataOutputStream(socket.getOutputStream());

out.writeUTF(t1.getText());

t1.setText("");

}catch(Exception e1){e1.printStackTrace();};

}

//ClientThread.java 代码

package message;

import java.net.*;

import java.io.*;

import javax.swing.*;

public class ClientThread extends Thread {

DataInputStream in;

JTextArea area;

public ClientThread(DataInputStream in,JTextArea area){

this.in=in;

this.area=area;

}

public void run()

{

while(true){

try{

String s=in.readUTF();

area.append(s);

}

catch(Exception e){e.printStackTrace();};

}

//Client.java代码

package message;

public class Client {

/**

* @param args

public static void main(String[] args) {

new ClientFrame();

}

// 每段代码都是个类，不要弄在一个文件里。运行 Client.java

good luck to you!

java线程的经典代码

package threadgroup;

class ThreadDemo3 extends Thread {

private String name;

private int delay;

public ThreadDemo3(String sname, int i_delay) {

name = sname;

delay = i_delay;

}

public void run() {

try {

sleep(delay);

} catch (InterruptedException e) {

}

System.out.println("多线程测试！\n" + name + "\n" + delay);

}

public class testMyThread {

public static void main(String[] args) {

ThreadDemo3 th1,th2,th3;

th1 = new ThreadDemo3("线程1", (int) (Math.random() * 900));

th2 = new ThreadDemo3("线程2", (int) (Math.random() * 900));

th3 = new ThreadDemo3("线程3", (int) (Math.random() * 900));

th1.start();

th2.start();

th3.start();

}

package threadgroup;

public class threadDemo {

public static void main(String[] args) {

Thread t = Thread.currentThread();

t.setName("你好吗？");

System.out.println("正在进行的Thread是：" + t);

try {

for (int i = 0; i 5; i++) {

System.out.println("我不叫穆继超" + i);

Thread.sleep(3000);

}

} catch (Exception e) {

// TODO: handle exception

System.out.println("Thread has wrong" + e.getMessage());

}

package threadgroup;

public class threadDemo2 implements Runnable {

public threadDemo2() {

Thread t1 = Thread.currentThread();

t1.setName("第一个主进程");

System.out.println("正在运行" + t1);

Thread t2 = new Thread(this, "");

System.out.println("在创建一个进程");

t2.start();

try {

System.out.println("使他进入第一个睡眠状态");

Thread.sleep(2000);

} catch (InterruptedException e) {

System.out.println("Thread has wrong" + e.getMessage());

}

System.out.println("退出第一个进程");

}

public void run() {

try {

for (int i = 0; i 5; i++) {

System.out.println("进程" + i);

Thread.sleep(3000);

}

} catch (InterruptedException e) {

// TODO: handle exception

System.out.println("Thread has wrong" + e.getMessage());

}

System.out.println("退出第二个进程");

}

public static void main(String[] args) {

new threadDemo2();

}

Java 的代码，50行，要三个函数，要有循环

随便给你写了一个

package com.wys.util;

import java.util.ArrayList;

import java.util.List;

import java.util.Random;

public class Test {

public static ListInteger smallNumbers,largeNumbers;

public static int sum1 = 0,sum2 = 0;

public static void main(String[] args) {

smallNumbers = new ArrayListInteger();

largeNumbers = new ArrayListInteger();

run();

}

public static void run() {

int i = 0;

for (int j = 0; j 50; j++) {

Random rand = new Random();

i = rand.nextInt(1000);

if (i500) {

small(i);

}else{

large(i);

}

System.out.println("随机输出的50个数字中:");

System.out.println("大于500的数（包括500）共有"+largeNumbers.size()+"个");

System.out.print("他们是"+largeNumbers);

System.out.println();

System.out.println("他们的和是"+sum1);

System.out.println("小于500的数共有"+smallNumbers.size()+"个");

System.out.print("他们是"+smallNumbers);

System.out.println();

System.out.println("他们的和是"+sum2);

}

private static void large(int number) {

largeNumbers.add(number);

sum1 += number;

}

private static void small(int number) {

smallNumbers.add(number);

sum2 += number;

}

求基础级java代码,150-200行,自己写的

我有计算器程序

import javax.swing.*;

import javax.swing.border.Border;

import java.awt.*;

import java.awt.event.ActionListener;

import java.awt.event.ActionEvent;

import java.math.BigDecimal;

import java.math.RoundingMode;

import java.util.HashMap;

/**

* 我的计算器。MyCalculator 继承于 JFrame，是计算器的界面

public class Calculator extends JFrame {

/**

private static final long serialVersionUID = 1L;

private Border border = BorderFactory.createEmptyBorder(5, 5, 5, 5);

private JTextField textbox = new JTextField("0");

private CalculatorCore core = new CalculatorCore();

private ActionListener listener = new ActionListener() {

public void actionPerformed(ActionEvent e) {

JButton b = (JButton) e.getSource();

String label = b.getText();

String result = core.process(label);

textbox.setText(result);

}

};

public Calculator(String title) throws HeadlessException {

super(title); // 调用父类构造方法

setupFrame(); // 调整窗体属性

setupControls(); // 创建控件

}

private void setupControls() {

setupDisplayPanel(); // 创建文本面板

setupButtonsPanel(); // 创建按钮面板

}

// 创建按钮面板并添加按钮

private void setupButtonsPanel() {

JPanel panel = new JPanel();

panel.setBorder(border);

panel.setLayout(new GridLayout(4, 5, 3, 3));

createButtons(panel, new String[]{

"7", "8", "9", "+", "C",

"4", "5", "6", "-", "CE",

"1", "2", "3", "*", "", // 空字符串表示这个位置没有按钮

"0", ".", "=", "/", ""

});

this.add(panel, BorderLayout.CENTER);

}

/**

* 在指定的面板上创建按钮

* @param panel 要创建按钮的面板

* @param labels 按钮文字

private void createButtons(JPanel panel, String[] labels) {

for (String label : labels) {

// 如果 label 为空，则表示创建一个空面板。否则创建一个按钮。

if (label.equals("")) {

panel.add(new JPanel());

} else {

JButton b = new JButton(label);

b.addActionListener(listener); // 为按钮添加侦听器

panel.add(b);

}

// 设置显示面板，用一个文本框来作为计算器的显示部分。

private void setupDisplayPanel() {

JPanel panel = new JPanel();

panel.setLayout(new BorderLayout());

panel.setBorder(border);

setupTextbox();

panel.add(textbox, BorderLayout.CENTER);

this.add(panel, BorderLayout.NORTH);

}

// 调整文本框

private void setupTextbox() {

textbox.setHorizontalAlignment(JTextField.RIGHT); // 文本右对齐

textbox.setEditable(false); // 文本框只读

textbox.setBackground(Color.white); // 文本框背景色为白色

}

// 调整窗体

private void setupFrame() {

this.setDefaultCloseOperation(EXIT_ON_CLOSE); // 当窗体关闭时程序结束

this.setLocation(100, 50); // 设置窗体显示在桌面上的位置

this.setSize(300, 200); // 设置窗体大小

this.setResizable(false); // 窗体大小固定

}

// 程序入口

public static void main(String[] args) throws Exception {

UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

Calculator frame = new Calculator("我的计算器");

frame.setVisible(true); // 在桌面上显示窗体

}

/**

* 计算器核心逻辑。这个逻辑只能处理 1~2 个数的运算。

class CalculatorCore {

private String displayText = "0"; // 要显示的文本

boolean reset = true;

int MaxLen = 30;

private BigDecimal number1, number2;

private String operator;

private HashMapString, Operator operators = new HashMapString, Operator();

private HashMapString, Processor processors = new HashMapString, Processor();

CalculatorCore() {

setupOperators();

setupProcessors();

}

// 为每种命令添加处理方式

private void setupProcessors() {

processors.put("[0-9]", new Processor() {