解决问题：将一个文件夹下以.java结尾的文件拷贝到a.txt文件中（源码拷贝）

代码实现：

import java.io.BufferedReader;import java.io.BufferedWriter;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.InputStreamReader;import java.io.OutputStreamWriter;/** * 复制文件夹下以java结尾的文件内容到一个文本文件 *  * @author 兴跃神话 * */public class CopyContent {	static BufferedWriter fw = null;	static{		FileOutputStream fos;		//目标文件		File file = new File("D:\\a.txt");		if(!file.exists()){			file.mkdirs();		}		try {			fos = new FileOutputStream(file);			fw = new BufferedWriter(new OutputStreamWriter(fos));		} catch (FileNotFoundException e) {			e.printStackTrace();		}	}	public static void main(String[] args) throws Exception {		//源文件所在目录		String filepath = "D:\\Workspaces\\MyeclipceWorkspace\\trainee";		copy(new File(filepath ));		fw.close();		System.out.println("复制完成！");	}	public static void copy(File file) throws Exception {		if (file.isDirectory()) {			File[] listFiles = file.listFiles();			for (File file2 : listFiles) {				copy(file2);			}		}		if (file.isFile() && file.getName().endsWith(".java")) {			fw.newLine();			fw.newLine();			fw.write(file.getName()+"源码:");			fw.newLine();			BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(file)));			String str = "";			while ((str = br.readLine()) != null) {				fw.write(str);				fw.newLine();			}			br.close();		}			}}