## Java专题十一（1）：IO [TOC] > IO是基于字节流和字符流操作的  **IO基类**: | | Reader |Writer |InputStream |OutputStream | | --- | --- | --- | --- | --- | | 字符流 | ✔ | ✔ | | | | 字节流 | | | ✔ | ✔ | | 输入流 | ✔ | | ✔ | | | 输出流 | | ✔ | | ✔ | **各种资源IO类**： | | Reader |Writer |InputStream |OutputStream | | --- | --- | --- | --- | --- | | File | FileReader | FileWriter| FileInputStream | FileOutputStream | | Buffer | BufferReader | BufferWriter | BufferedInputStream | BufferedOutputStream | | Pipe | PipedReader | PipedWriter| PipedInputStream | PipedOutputStream | | String | StringReader | StringWriter| | | | ByteArray | ByteArrayReader | ByteArrayWriter| ByteArrayInputStream | ByteArrayOutputStream | | CharArray | CharArrayReader | CharArrayWriter| | | | Object | | |ObjectInputStream | ObjectOutputStream | | Filter | FilterReader | FilterWriter| FilterInputStream | FilterOutputStream | | Data | | | DataInputStream | DataOutputStream | ### 1.字节流转换成字符（InputStreamReader） ``` public static String byte2Char(InputStream is, String charsetName) throws IOException { if (charsetName == null || !Charset.isSupported(charsetName)){ charsetName = DEFAULT_CHARSET; } InputStreamReader isr = new InputStreamReader(is, charsetName); char[] cbuf = new char[DEFAULT_BYTE_SIZE]; StringBuilder sbf = new StringBuilder(); int readCount; while((readCount = isr.read(cbuf)) > 0){ sbf.append(cbuf, 0, readCount); } return sbf.toString(); } ``` ### 2.从文件中读取字符（FileReader） ``` public static String readCharFromFile(String path) throws IOException { File fi = new File(path); if (fi.exists() && fi.isFile()){ FileReader fr = new FileReader(fi); char[] cbuf = new char[DEFAULT_CHAR_SIZE]; int readCount; StringBuilder sbf = new StringBuilder(); while((readCount = fr.read(cbuf)) > 0){ sbf.append(cbuf, 0, readCount); } return sbf.toString(); } throw new FileNotFoundException(); } ``` ### 3.字节流输出到文件（FileOutputStream） ``` public static File writeByteToFile(InputStream is, String path, boolean append) throws IOException { File fi = new File(path); // create file first if not exists if (!fi.exists()) { fi.createNewFile(); append = false; } FileOutputStream fos = new FileOutputStream(fi, append); byte[] buf = new byte[DEFAULT_BYTE_SIZE]; int readCount; while((readCount = is.read(buf)) > 0){ fos.write(buf, 0, readCount); } fos.close(); is.close(); return fi; } ``` ### 4.字符输出到文件（FileWriter） ``` public static File writeCharToFile(String content, String path, boolean append) throws IOException { File fi = new File(path); // create file first if not exists if (!fi.exists()) { fi.createNewFile(); append = false; } FileWriter fw = new FileWriter(fi, append); fw.write(content, 0, content.length()); fw.close(); return fi; } ``` 字节流转换成字符流，文件与字节，文件与字符转换操作完整代码见： [IOTools](https://github.com/15045120/git-docs/blob/master/tools/IOTools.java)