一个java文件里面最多写多少行代码？
hotspot 虚拟机（咱们平时开发用的sun公司的虚拟机，其他两大商用虚拟机是BEA的JRockit和IBM的J9）里面两个字节来限制大小，所以最多65536行，超过javac会无法编译。而且一个Java方法不能超过64k。一般一个Java类不要有太多行数，如果一个Java代码超过几千甚至过万，个人觉得应该考虑一些代码优化方式，比如继承；或者重新构思这个类。代码行数太多可读性查，不利于维护。
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求java小程序代码，500行左右。。大作业用。追加50
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class mypanel extends Panel implements MouseListener
{
int chess[][] = new int[11][11];
boolean Is_Black_True;
mypanel()
{
Is_Black_True = true;
for(int i = 0;i 11;i++)
{
for(int j = 0;j 11;j++)
{
chess[i][j] = 0;
}
}
addMouseListener(this);
setBackground(Color.BLUE);
setBounds(0, 0, 360, 360);
setVisible(true);
}
public void mousePressed(MouseEvent e)
{
int x = e.getX();
int y = e.getY();
if(x 25 || x 330 + 25 ||y 25 || y 330+25)
{
return;
}
if(chess[x/30-1][y/30-1] != 0)
{
return;
}
if(Is_Black_True == true)
{
chess[x/30-1][y/30-1] = 1;
Is_Black_True = false;
repaint();
Justisewiner();
return;
}
if(Is_Black_True == false)
{
chess[x/30-1][y/30-1] = 2;
Is_Black_True = true;
repaint();
Justisewiner();
return;
}
}
void Drawline(Graphics g)
{
for(int i = 30;i = 330;i += 30)
{
for(int j = 30;j = 330; j+= 30)
{
g.setColor(Color.WHITE);
g.drawLine(i, j, i, 330);
}
}
for(int j = 30;j = 330;j += 30)
{
g.setColor(Color.WHITE);
g.drawLine(30, j, 330, j);
}
}
void Drawchess(Graphics g)
{
for(int i = 0;i 11;i++)
{
for(int j = 0;j 11;j++)
{
if(chess[i][j] == 1)
{
g.setColor(Color.BLACK);
g.fillOval((i + 1) * 30 - 8, (j + 1) * 30 - 8, 16, 16);
}
if(chess[i][j] == 2)
{
g.setColor(Color.WHITE);
g.fillOval((i + 1) * 30 - 8, (j + 1) * 30 - 8, 16, 16);
}
}
}
}
void Justisewiner()
{
int black_count = 0;
int white_count = 0;
int i = 0;
for(i = 0;i 11;i++)//横向判断
{
for(int j = 0;j 11;j++)
{
if(chess[i][j] == 1)
{
black_count++;
if(black_count == 5)
{
JOptionPane.showMessageDialog(this, "黑棋胜利");
Clear_Chess();
return;
}
}
else
{
black_count = 0;
}
if(chess[i][j] == 2)
{
white_count++;
if(white_count == 5)
{
JOptionPane.showMessageDialog(this, "白棋胜利");
Clear_Chess();
return;
}
}
else
{
white_count = 0;
}
}
}
for(i = 0;i 11;i++)//竖向判断
{
for(int j = 0;j 11;j++)
{
if(chess[j][i] == 1)
{
black_count++;
if(black_count == 5)
{
JOptionPane.showMessageDialog(this, "黑棋胜利");
Clear_Chess();
return;
}
}
else
{
black_count = 0;
}
if(chess[j][i] == 2)
{
white_count++;
if(white_count == 5)
{
JOptionPane.showMessageDialog(this, "白棋胜利");
Clear_Chess();
return;
}
}
else
{
white_count = 0;
}
}
}
for(i = 0;i 7;i++)//左向右斜判断
{
for(int j = 0;j 7;j++)
{
for(int k = 0;k 5;k++)
{
if(chess[i + k][j + k] == 1)
{
black_count++;
if(black_count == 5)
{
JOptionPane.showMessageDialog(this, "黑棋胜利");
Clear_Chess();
return;
}
}
else
{
black_count = 0;
}
if(chess[i + k][j + k] == 2)
{
white_count++;
if(white_count == 5)
{
JOptionPane.showMessageDialog(this, "白棋胜利");
Clear_Chess();
return;
}
}
else
{
white_count = 0;
}
}
}
}
for(i = 4;i 11;i++)//右向左斜判断
{
for(int j = 6;j = 0;j--)
{
for(int k = 0;k 5;k++)
{
if(chess[i - k][j + k] == 1)
{
black_count++;
if(black_count == 5)
{
JOptionPane.showMessageDialog(this, "黑棋胜利");
Clear_Chess();
return;
}
}
else
{
black_count = 0;
}
if(chess[i - k][j + k] == 2)
{
white_count++;
if(white_count == 5)
{
JOptionPane.showMessageDialog(this, "白棋胜利");
Clear_Chess();
return;
}
}
else
{
white_count = 0;
}
}
}
}
}
void Clear_Chess()
{
for(int i=0;i11;i++)
{
for(int j=0;j11;j++)
{
chess[i][j]=0;
}
}
repaint();
}
public void paint(Graphics g)
{
Drawline(g);
Drawchess(g);
}
public void mouseExited(MouseEvent e){}
public void mouseEntered(MouseEvent e){}
public void mouseReleased(MouseEvent e){}
public void mouseClicked(MouseEvent e){}
}
class myframe extends Frame implements WindowListener
{
mypanel panel;
myframe()
{
setLayout(null);
panel = new mypanel();
add(panel);
panel.setBounds(0,23, 360, 360);
setTitle("单人版五子棋");
setBounds(200, 200, 360, 383);
setVisible(true);
addWindowListener(this);
}
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
public void windowDeactivated(WindowEvent e){}
public void windowActivated(WindowEvent e){}
public void windowOpened(WindowEvent e){}
public void windowClosed(WindowEvent e){}
public void windowIconified(WindowEvent e){}
public void windowDeiconified(WindowEvent e){}
}
public class mywindow
{
public static void main(String argc [])
{
myframe f = new myframe();
}
}
一个java管理系统多少行代码
1，java规范中一般不建议一个java类中超过500行
2，一行的长度不超过200个
3，按照规定格式将代码格式化
需要一份500行的java程序，期末大作业，最好带详细注释。
Java生成CSV文件简单操作实例
CSV是逗号分隔文件(Comma Separated Values)的首字母英文缩写，是一种用来存储数据的纯文本格式，通常用于电子表格或数据库软件。在 CSV文件中，数据“栏”以逗号分隔，可允许程序通过读取文件为数据重新创建正确的栏结构，并在每次遇到逗号时开始新的一栏。如：
123 1,张三,男2,李四,男3,小红,女
Java生成CSV文件（创建与导出封装类）
package com.yph.omp.common.util;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.beanutils.BeanUtils;
import org.junit.Test;
/**
* Java生成CSV文件
*/
public class CSVUtil {
/**
* 生成为CVS文件
*
* @param exportData
* 源数据List
* @param map
* csv文件的列表头map
* @param outPutPath
* 文件路径
* @param fileName
* 文件名称
* @return
*/
@SuppressWarnings("rawtypes")
public static File createCSVFile(List exportData, LinkedHashMap map,
String outPutPath, String fileName) {
File csvFile = null;
BufferedWriter csvFileOutputStream = null;
try {
File file = new File(outPutPath);
if (!file.exists()) {
file.mkdir();
}
// 定义文件名格式并创建
csvFile = File.createTempFile(fileName, ".csv",
new File(outPutPath));
// UTF-8使正确读取分隔符","
csvFileOutputStream = new BufferedWriter(new OutputStreamWriter(
new FileOutputStream(csvFile), "GBK"), 1024);
// 写入文件头部
for (Iterator propertyIterator = map.entrySet().iterator(); propertyIterator
.hasNext();) {
java.util.Map.Entry propertyEntry = (java.util.Map.Entry) propertyIterator
.next();
csvFileOutputStream
.write("\"" + (String) propertyEntry.getValue() != null ? (String) propertyEntry
.getValue() : "" + "\"");
if (propertyIterator.hasNext()) {
csvFileOutputStream.write(",");
}
}
csvFileOutputStream.newLine();
// 写入文件内容
for (Iterator iterator = exportData.iterator(); iterator.hasNext();) {
Object row = (Object) iterator.next();
for (Iterator propertyIterator = map.entrySet().iterator(); propertyIterator
.hasNext();) {
java.util.Map.Entry propertyEntry = (java.util.Map.Entry) propertyIterator
.next();
/*-------------------------------*/
//以下部分根据不同业务做出相应的更改
StringBuilder sbContext = new StringBuilder("");
if (null != BeanUtils.getProperty(row,(String) propertyEntry.getKey())) {
if("证件号码".equals(propertyEntry.getValue())){
//避免：身份证号码 ，读取时变换为科学记数 - 解决办法：加 \t(用Excel打开时，证件号码超过15位后会自动默认科学记数)
sbContext.append(BeanUtils.getProperty(row,(String) propertyEntry.getKey()) + "\t");
}else{
sbContext.append(BeanUtils.getProperty(row,(String) propertyEntry.getKey()));
}
}
csvFileOutputStream.write(sbContext.toString());
/*-------------------------------*/
if (propertyIterator.hasNext()) {
csvFileOutputStream.write(",");
}
}
if (iterator.hasNext()) {
csvFileOutputStream.newLine();
}
}
csvFileOutputStream.flush();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
csvFileOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return csvFile;
}
/**
* 下载文件
*
* @param response
* @param csvFilePath
* 文件路径
* @param fileName
* 文件名称
* @throws IOException
*/
public static void exportFile(HttpServletRequest request,
HttpServletResponse response, String csvFilePath, String fileName)
throws IOException {
response.setCharacterEncoding("UTF-8");
response.setContentType("application/csv;charset=GBK");
response.setHeader("Content-Disposition", "attachment; filename="
+ new String(fileName.getBytes("GB2312"), "ISO8859-1"));
InputStream in = null;
try {
in = new FileInputStream(csvFilePath);
int len = 0;
byte[] buffer = new byte[1024];
OutputStream out = response.getOutputStream();
while ((len = in.read(buffer)) 0) {
out.write(buffer, 0, len);
}
} catch (FileNotFoundException e1) {
System.out.println(e1);
} finally {
if (in != null) {
try {
in.close();
} catch (Exception e1) {
throw new RuntimeException(e1);
}
}
}
}
/**
* 删除该目录filePath下的所有文件
*
* @param filePath
* 文件目录路径
*/
public static void deleteFiles(String filePath) {
File file = new File(filePath);
if (file.exists()) {
File[] files = file.listFiles();
for (int i = 0; i files.length; i++) {
if (files[i].isFile()) {
files[i].delete();
}
}
}
}
/**
* 删除单个文件
*
* @param filePath
* 文件目录路径
* @param fileName
* 文件名称
*/
public static void deleteFile(String filePath, String fileName) {
File file = new File(filePath);
if (file.exists()) {
File[] files = file.listFiles();
for (int i = 0; i files.length; i++) {
if (files[i].isFile()) {
if (files[i].getName().equals(fileName)) {
files[i].delete();
return;
}
}
}
}
}
@SuppressWarnings({ "unchecked", "rawtypes" })
@Test
public void createFileTest() {
List exportData = new ArrayListMap();
Map row1 = new LinkedHashMapString, String();
row1.put("1", "11");
row1.put("2", "12");
row1.put("3", "13");
row1.put("4", "14");
exportData.add(row1);
row1 = new LinkedHashMapString, String();
row1.put("1", "21");
row1.put("2", "22");
row1.put("3", "23");
row1.put("4", "24");
exportData.add(row1);
LinkedHashMap map = new LinkedHashMap();
map.put("1", "第一列");
map.put("2", "第二列");
map.put("3", "第三列");
map.put("4", "第四列");
String path = "d:/export";
String fileName = "文件导出";
File file = CSVUtil.createCSVFile(exportData, map, path, fileName);
String fileNameNew = file.getName();
String pathNew = file.getPath();
System.out.println("文件名称：" + fileNameNew );
System.out.println("文件路径：" + pathNew );
}
}
//注：BeanUtils.getProperty(row,(String) propertyEntry.getKey()) + "\t" ，只为解决数字格式超过15位后，在Excel中打开展示科学记数问题。
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