java中的文件操作：读取写入byte[]字节流、string字符串、list列表

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全栈工程师开发手册（作者：栾鹏）

java教程全解

java中文件操作：读取文件成字节流，将字节流写入文件，按行读取文件成字符串列表，将字符串列表存储成文件，读取文件成字符串，将字符串写入文件。

主程序测试文件

    //测试程序    public static void main(String[] args)     {                byte[] data=file2byte("test.txt");                  //读取文件        byte2file("test1.txt",data);                        //写入文件        ArrayList<String> allline=file2list("test.txt","UTF-8");    //按行读取文件        list2file("test2.txt",allline,"UTF-8");                     //存储文件        String content=file2str("test.txt","UTF-8");                //读取文件        str2file("test3.txt",content,"UTF-8");                      //存储文件    }

读取文件成字节数组

    public static byte[] file2byte(String path)    {        try {            FileInputStream in =new FileInputStream(new File(path));            //当文件没有结束时，每次读取一个字节显示            byte[] data=new byte[in.available()];            in.read(data);            in.close();            return data;        } catch (Exception e) {            e.printStackTrace();            return null;        }    }

将字节数组写入文件

    public static void byte2file(String path,byte[] data) {        try {            FileOutputStream outputStream  =new FileOutputStream(new File(path));            outputStream.write(data);            outputStream.close();        } catch (Exception e) {            e.printStackTrace();        }    }

按行读取文件成list

    public static ArrayList<String> file2list(String path,String encoder) {        ArrayList<String> alline=new ArrayList<String>();        try {            BufferedReader in =new BufferedReader(new InputStreamReader(new FileInputStream(path),encoder));            String str=new String();            while ((str=in.readLine())!=null) {                alline.add(str);            }            in.close();        } catch (Exception e) {            e.printStackTrace();        }        return alline;    }

输出list到文件

    public static void list2file(String path,ArrayList<String> data,String encoder)     {        try {            BufferedWriter out =new BufferedWriter(new OutputStreamWriter(new FileOutputStream(path),encoder));            for (String str:data) {                out.write(str);                out.newLine();            }            out.flush();            out.close();        } catch (Exception e) {            e.printStackTrace();        }    }

从标准输入中读入

    public static String system2str() throws IOException{        BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in));        return stdin.readLine();    }

读取文件成字符串

    public static String file2str(String path,String encoder)     {        StringBuilder sb=new StringBuilder();        try {            BufferedReader in =new BufferedReader(new InputStreamReader(new FileInputStream(path),encoder));            String str=new String();            while ((str=in.readLine())!=null) {                sb.append(str);            }            in.close();         } catch (Exception e) {            e.printStackTrace();        }        return sb.toString();    }

输出字符串到文件

    public static void str2file(String path,String data,String encoder)     {        try {            BufferedWriter out =new BufferedWriter(new OutputStreamWriter(new FileOutputStream(path),encoder));            out.write(data);            out.flush();            out.close();        } catch (Exception e) {            e.printStackTrace();        }    }

读取文件成数据矩阵

    public static ArrayList<Double> file2matrix(String path)     {        ArrayList<Double> alldata=new ArrayList<Double>();        try {            DataInputStream in=new DataInputStream(new BufferedInputStream(new FileInputStream(path)));            //利用DataInputStream来读数据            while(true)            {                alldata.add(in.readDouble());            }        } catch (Exception e) {            e.printStackTrace();        }        return alldata;    }

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