021.2 IO stream - byte output stream

The abstract base class of byte stream: InputStream, the abstract base class of OutputStream
character stream: Reader, Writer
The subclass names derived from these four classes are all suffixed with the parent class name as the subclass name. Such as: InputStream subclass FileInputStream, Reader subclass FileReader

################################################## #file
write, byte output stream

private  static  final String LINE_SEPARATOR = System.getProperty("line.separator");          // Get the system newline for newline 
public  static  void main(String[] args) throws IOException
{
    System.out.println(LINE_SEPARATOR);
    String s = "花"+LINE_SEPARATOR+"awegadjgaw";
    File dir = new File("abc");
    if(!dir.exists()){
        dir.mkdir ();
    }
    FileOutputStream fos = new FileOutputStream("abc\\ai.txt", true );          // true means can continue to write 
    fos.write(s.getBytes());             // write information 
    System.out.println("ok" );
    fos.close();

}

 

##########Exception Handling

public static void main(String[] args)
{
    FileOutputStream fos = null ;     // Declare outside try, and close try in finally 
    {
        fos = new FileOutputStream("abc"+File.separator+"ai.txt");
        fos.write("aiqing".getBytes());
    }
    catch(IOException e){
    }
    finally {
         if (fos != null ){              // Before releasing resources, judge whether it is empty 
            try {
                fos.close();
            }
            catch(IOException e){
                throw new RuntimeException(e);
            }
        }
    }
}

###########################################Exercise
to get a specific folder Collection of files: filters are used

public static void main(String[] args)
{
    File f = new File("f:"+File.separator+"eclipse_javaCode"+File.separator+
            "day21"+File.separator+"day19");
//        System.out.println(f);
    List<File> list = getList(f,".java");
    for(File file:list){
        System.out.println(file);
    }
}
private static List<File> getList(File dir, String string)
{
    List<File> list = new ArrayList<File>();
    FileFilter filter = new FileFilterByEnding(string);
    getFileList(dir,list,filter);
    return list;
}
private static void getFileList(File dir, List<File> list, FileFilter filter)
{
    // Get the file array 
    File[] files = dir.listFiles();
     // Traverse the file array 
    for (File file:files){
         if (file.isDirectory()){
            getFileList(file, list, filter);
        }
        else{
            if(filter.accept(file)){
                list.add(file);
            }
        }
    }
}

with main function

public class FileFilterByEnding implements FileFilter
{
    private String suffix;
    public FileFilterByEnding(String suffix) {
        super();
        this.suffix = suffix;
    }
    @Override
    public boolean accept(File pathname)
    {
        return pathname.getName().endsWith(suffix);
    }
}

filter class