java文件读取操作笔记

按行读取、整体读取
BufferedReader reader=new BufferedReader(new FileReader("D:/baidu/Desktop/acctinfo201612.csv"));
String l,s;
int row=0,col=0;
l=reader.readLine();
col=l.split(",").length;
System.out.println(reader.readLine());
while((l=reader.readLine()) !=null){
row++;
// if(row<=6){
// System.out.println(l);
// s=l.split("\t")[0];
//
// }
}
reader.close();
System.out.println("rows:"+row+" cols:"+col);



File file=new File("src/file/sql_bj");
//分行读取
// BufferedReader reader=new BufferedReader(new FileReader(file));
// reader.mark( ( int )file.length() + 1 );//标记
// String l;
// while((l=reader.readLine())!=null){
// System.out.println(l);
// }
// reader.reset();//回到起点
// while((l=reader.readLine())!=null){
// System.out.println(l);
// }

//一次读取
        FileReader reader1 = new FileReader(file);
        int fileLen = (int)file.length();
        char[] chars = new char[fileLen];
        reader1.read(chars);
        String txt = String.valueOf(chars);
        System.out.println(txt);


按字符集读取：
String encode="gbk";
ArrayList a=new ArrayList();
FileInputStream fis = new FileInputStream("D:/baidu/Desktop/a.txt");  
InputStreamReader isw = new InputStreamReader(fis, encode);  
BufferedReader br = new BufferedReader(isw);


判断文件存在、创建文件、写内容到文件、遍历文件夹、文件重命名：
String l,name="";
File p=new File(args[0]);
// File q=new File("D:\\baidu\\Desktop\\新建文本文档.csv");
// if(!q.exists()){
// q.createNewFile();
// System.out.println("aaa");
// }
FileWriter fw = new FileWriter("D:\\baidu\\Desktop\\temp_hebingzhanghu.csv");
File[] fs=p.listFiles();
fw.write("账户ID,账户名称,运营单位"+"\n");
int i=1;
for (File f:fs){
if(f.getName().indexOf("csv")!=-1){
BufferedReader reader=new BufferedReader(new FileReader(f.getPath()));
l=reader.readLine();
while((l=reader.readLine()) !=null){
fw.write(l+"\n");
i++;
}
name="acct_info_shiduan "+f.getName().substring(9);
}
}
fw.close();
new File("D:\\baidu\\Desktop\\temp_hebingzhanghu.csv").renameTo(new File("D:\\baidu\\Desktop\\"+name));
System.out.println(i);