java io操作_java IO操作

java7中引入自动资源管理(ARM)，使用try(){}catch{}finally{},()中的资源会在程序运行后自动释放。

文件流分为输入流和输出流，典型用法

FileReader fr = new FileReader("poem.txt");           //读取已有文件

FileWriter fw = new FileWriter("newPoem2.txt")；   //向特定名文件写入(不存在先创建)，覆盖

char[] cbuf = new char[32];                   //Reader和Writer读写以字符为单位

int hasRead = 0;              //返回一次读取数

while ((hasRead = fr.read(cbuf)) > 0)

{

fw.write(cbuf,0,hasRead);

}

FileInputStream fis = new FileInputStream("poem.txt");

FileOutputStream fos = new FileOutputStream("newPoem.txt"))

byte[] bbuf = new byte[32];                //InputStream和OutputStream读写以字节为单位

int hasRead = 0;

while ((hasRead = fis.read(bbuf)) > 0)

{

fos.write(bbuf,0,hasRead);

}

java建议称，处理流PrintWriter功能比较强大，建议将输出流包装成PrintStream后进行输出，类似的将Writer包装成PrintWriter

FileInputStream fis = new FileInputStream("poem.txt");

FileOutputStream fos = new FileOutputStream("test.txt");

PrintStream ps = new PrintStream(fos);

FileReader fr = new FileReader("poem.txt");

FileWriter fw = new FileWriter("text.java");

PrintWriter pw = new PrintWriter(fw)

char[] cbuf = new char[32];

byte[] bbuf = new byte[32];

int hasRead = 0;

while ((hasRead = fis.read(bbuf))>0)

{

ps.write(bbuf,0,hasRead);

}

while ((hasRead = fr.read(cbuf)) > 0)

{

pw.write(cbuf,0,hasRead);

}

PrintStream、PrintWriter、BufferedReader

PrintStream用于处理字节流，PrintWriter用于处理字符流

其中bufferedReader的readLine()方法在读取数据时，在该方法成功返回之前，线程将一直阻塞，考虑到这个原因，当要实现多个文件并发读取时，应为每个读取过程启动一个线程