Java常见小功能备忘录

Java文件读写：

##Java文件读写：
String path="/home/hadoop/spark/practice_data/out.dat";
FileOutputStream fileos=new FileOutputStream(path);
ObjectOutputStream objectos=new ObjectOutputStream(fileos);
objectos.flush();
fileos.close();//记得要关闭，不然不会写出结果来
objectos.close();           

Java文件读写-读一行中文：

//读取一行中文
    public static void readLine(String path) throws IOException {
        FileInputStream fis=new FileInputStream(path);
        InputStreamReader isr=new InputStreamReader(fis, "UTF-8");
        BufferedReader br = new BufferedReader(isr);        
        String line="";        
        while ((line=br.readLine())!=null) {
            //arrs=line.split(",");
            //System.out.println(arrs[0]);
            System.out.println(line);
        }
        br.close();
        isr.close();
        fis.close();
    }

获取系统时间

long begin = System.currentTimeMillis();

String Format

String str_accuracy=String.format(" accuracy = %.4f ", accuracy);