Java中读文件操作


InputStream & Reader


  • InputStream(字节流),如下是InputStream的层次结构:

public class audioInputStream {
    public static void playWAV(){
        try {
            AudioInputStream stream = AudioSystem.getAudioInputStream(new File("SourceFile/1.wav"));
            byte[] samples = getSamples(stream);   //将音频转化为字节数组
            InputStream in = new ByteArrayInputStream(samples);
            play(in,stream.getFormat());    //播放音频文件
        } catch (UnsupportedAudioFileException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
    }
    private static byte[] getSamples(AudioInputStream stream){
        int length = (int) (stream.getFrameLength()*stream.getFormat().getFrameSize());
        byte[] samples = new byte[length];
        DataInputStream in = new DataInputStream(stream);
        try {
            in.readFully(samples);
            System.out.println(length);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return samples;
    }
    private static void play(InputStream stream, AudioFormat format){
        int bufferSize = format.getFrameSize()* Math.round(format.getSampleRate()/10);
        byte[] buffer = new byte[bufferSize];
        DataLine.Info info = new DataLine.Info(SourceDataLine.class, format);
        try {
            SourceDataLine line = (SourceDataLine) AudioSystem.getLine(info);
            line.open(format, bufferSize);
            line.start();
            int numBytesRead = 0;
            while(numBytesRead != -1){
                numBytesRead = stream.read(buffer, 0, buffer.length);
                if(numBytesRead != -1){
                    line.write(buffer, 0, numBytesRead);
                    //System.out.println(numBytesRead);
                }
            }
            line.drain();
            line.close();
        } catch (LineUnavailableException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
  • ByteArrayInputStream:流的来源并不一定是文件,也可以是内存中的一块空间,例如一个字节数组。ByteArrayInputStream就是将字节数组当作流输入来源的类。
    • new ByteArrayInputStream(byte[] buf, int offset, int length)
    • new ByteArrayInputStream(byte[] buf)
  • FileInputStream:从文件系统或者终端获取输入信息,构造函数如下:
    • new FileInputStream(File file)
    • new FileInputStream(FileDescriptor fdObj)
    • new FileInputStream(String name)
try {
    FileInputStream fis = new FileInputStream("SourceFile/employee");
    try {
        byte[] bytes = new byte[fis.available()];
        fis.read(bytes);
        fis.close();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
} catch (FileNotFoundException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
  • Reader(字符输入流),其层次结构如下:

  • BufferedReader:字符读入,默认拥有8192字符的缓冲区,当BufferedReader在读取文本文件时,会先尽量从文件中读入字符数据并置入缓冲区,而之后若使用read()方法,会先从缓冲区中进行读取。如果缓冲区数据不足,才会再从文件中读取。
    • 构造方法有两个,size表示设置缓冲区大小,默认为8192:
      • new BufferedReader(Reader in)
      • new BufferedReader(Reader in, int size)
    • //System.in是一个位流,为了转换为字符流,可使用InputStreamReader为其进行字符转换,
      //然后再使用BufferedReader为其增加缓冲功能。
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      String content = null;
      try {
          while(!(content = br.readLine()).equals("quit")){
              System.out.println(content);
          }
          br.close();
      } catch (IOException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
      }
  • CharArrayReader:从字符数组中读取信息
    • 构造方法有两个:
      • new CharArrayReader(char[] buf)
      • new CharArrayReader(char[] buf, int offset, int length)
    • 相关说明见CharArrayReader类链接。
  • InputStreamReader:将字节流转换为字符流。是字节流通向字符流的桥梁。如果不指定字符集编码,该解码过程将使用平台默认的字符编码。
    • 构造方法:
      • new InputStreamReader(InputStream in)
      • new InputStreamReader(InputStream in, Charset cs)
      • new InputStreamReader(InputStream in, CharsetDecoder dec)
      • new InputStreamReader(InputStream in, String charsetName)
    • 相关说明见InputStreamReader类链接。
  • StringReader:读入String字符串。
    • 构造方法
      • new StringReader(String str)
    • 相关代码
    • StringReader sr = new StringReader("dsfasdfasdfasd");
      char[] chars = new char[5];   //每次读取5个字符
      int length = 0;
      try {
           while((length = sr.read(chars)) != -1){
           String strRead = new String(chars, 0, length).toUpperCase();  
           System.out.println(strRead);  
           }
      } catch (IOException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
      }
posted @ 2016-09-20 08:01  best.lei  阅读(1702)  评论(0编辑  收藏  举报