Java的IO操作

1.读取文件到内存中

InputStream is = new FileInputStream(filename);

InputStreamReader reader = new InputStreamReader(is);

try{

    BufferedReader in = new BufferedReader(reader);

    //BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream(filename)));

     //BufferedReader in = new BufferedReader(new FileReader(new File(filename));

    String buf = null;

    StringBuffer textBuf = new StringBuffer();

    while((buf = in.readLine()) != null){

        textBuf.append(buf);

        textBuf.append("\n");

    }

    in.close();

}catch(Exception e){    

}finally{

}

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如何利用文件过滤器，获取想要的文件：

File[] files = directory.listFiles(new FilenameFilter() {

public boolean accept(File d, String name) {

return name.endsWith(".txt");

}

});

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2.记录日志到本地磁盘

try{

BufferedWriter writer = new BufferedWriter(new FileWriter(new File("c:\\text\\ClassficationResult.txt"),true));

writer.write("=============判断错误count============" + count + "\r\n");

writer.write("=================结束===============" + "\r\n");

writer.close();

}catch(Exception e){

e.printStackTrace();

}

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3.获取从console控制台输入的int类型的数字

Scanner in = new Scanner(System.in);

    int i = in.nextInt();

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4.获取系统的当前时间

DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH-mm-ss sss");

//private java.text.SimpleDateFormat fromat = new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date date = new Date();
 df.format(date);

HH：指的是24小时制；hh：指的是12小时制；

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5.批量将给定的文件夹下的txt文本文档进行拆分，然后将拆分的内容分别写到给定的路径中去，自动创建文件夹，名字为txt文本文档的名字，拆分的内容保存的名字从0.txt--结束。

static void test6(){

String readPath = "E:\\CODE\\wtest2\\";

String writePath = "E:\\CODE\\wtest\\";

String result = "";

String filePath = "";

String[] strResult = null;

System.out.println("begin...");

File filetest6 = new File(readPath);

if(filetest6.isDirectory()){

String[] filenamelist = filetest6.list();

for(int n = 0; n < filenamelist.length; n++){

filePath = readPath + filenamelist[n];

// System.out.println(filePath);

//如果文件夹不存在则创建一个新的文件夹；

File fileCreate = new File(writePath + filenamelist[n].substring(0, filenamelist[n].lastIndexOf(".")));

if(!fileCreate.exists()){

fileCreate.mkdir();

}

try{

//从目标文件夹中读取文本文件并拆分成字符串

BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(filePath), "Unicode"));

String str = "";

StringBuffer strBuffer = new StringBuffer();

while((str = br.readLine()) != null){

strBuffer.append(str);

strBuffer.append("\n");

}

br.close();

result = strBuffer.toString();

strResult = result.split("\n");

// System.out.println(result);

//向目标文件中写如文件

for(int i = 0; i < strResult.length; i ++){

BufferedWriter writer = new BufferedWriter(new FileWriter(fileCreate.getAbsolutePath() + File.separator + i + ".txt"));

writer.write(strResult[i]);

writer.close();

}

}catch (Exception e) {

}

}

}

System.out.println("done");

}

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7.String类型的字符串；进行删减的例子

String str = "corpus_数据库.txt";

// str = str.substring(0, str.length() - 4);

str = str.substring(0, str.lastIndexOf("."));

    结果都一样：corpus_数据库，即就是去掉后缀“。txt”

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8.获取到给定路径下的所有文件夹的信息

File file = new File(testPath);

File files[] = file.listFiles(new java.io.FileFilter() {

            public boolean accept(File f) {

                return f.isDirectory() && !f.isHidden();

            }

        });

for(File f : files){

System.out.println(f.getName());

}

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9.