封装文件读取、写入，文件拷贝与文件夹拷贝

封装类：

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;

/*
 * 封装文件读取、写入，拷贝与文件夹的拷贝
 */
public class FileUtil {
//读取文件
public static String readfile(File src,File dest) {
return readfile(src.getAbsoluteFile(),dest.getAbsoluteFile());
    }
public static String readfile(String src,String dest) {
        String retString = "";
//1、建立关联
        File file = new File(src);
//2、选择流
        InputStream stream = null;
try {
            stream = new FileInputStream(file);
//3、确定一次读取字节大小
byte[] size = new byte[1024];
int len = 0;//每次读取字节数
//4、循环读取
while(-1!=(len = stream.read(size))){//读取失败返回-1
                String info = new String(size,0,len);
                retString += info;
if(null!=dest){
                    writefile(dest,size);
                }
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
if(stream!=null){
try {
                    stream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
return retString;
    }

//写出文件
public static void writefile(String dest,String str) {
        writefile(dest,str.getBytes());
    }
public static void writefile(String dest,byte[] size) {
        File file = new File(dest);
if(!file.exists()){
try {
                file.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        OutputStream stream = null;
try {
            stream = new FileOutputStream(file,true);
//字符串转字符数组
            stream.write(size,0,size.length);
            stream.flush();//强制刷新出去
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
if(null!=stream){
try {
                    stream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
//拷贝文件
public static void copyFile(File src,File dest) {
        copyFile(src.getAbsoluteFile(),dest.getAbsoluteFile());
    }
public static void copyFile(String src,String dest) {
        readfile(src, dest);
    }
//拷贝文件夹
public static void copyDir(String src,String dest) {
        File srcData = new File(src);
        File desData = null;
if(srcData.isDirectory()){
            desData = new File(dest,srcData.getName());
        }
        copyDirdetails(srcData,desData);
    }
private static void copyDirdetails(File src,File dest) {
if(src.isFile()){//文件
            CopyFile.copyFile(src.getAbsolutePath(), dest.getAbsolutePath());
        }else{
if(src.isDirectory()){//文件夹
//确保目标文件夹存在
                dest.mkdirs();
//获取下一级目录|文件
for(File sub:src.listFiles()){
                    copyDirdetails(sub,new File(dest,sub.getName()));
                }
            }
        }
    }
}

测试类：

public class FileUtiltest {
public static void main(String[] args) {
        FileUtil.copyFile("E:/test.txt", "D:/a.txt");
        System.out.println(FileUtil.readfile("E:/test.txt", null));
        FileUtil.writefile("E:/d.txt", "my name is hu cheng peng.");
        FileUtil.copyDir("D:/JAVA/Workspaces/MyEclipse 8.6/SloarModel", "E:/");
    }
}