java io流

Java 流在处理上分为字符流和字节流。字符流处理的单元为 2 个字节的 Unicode 字符，分别操作字符、字符数组或字符串，而字节流处理单元为 1 个字节，操作字节和字节数组。
当读不到数据时方法就返回-1

注： 每次以1024字节或其他指定数读取文件 然后转换成String类型，可能会有乱码问题

( 一 )以字节为导向的 stream------InputStream/OutputStream
( 二 )以字符为导向的 stream Reader/Writer

public final class FileUtil {
private FileUtil() {
}

/**
* 从指定的文件路径中读取文件.
*
* @param filePath
*            文件的全路径名,包括文件名
* @return String 文件的内容
* @throws IOException
*/
public static String read(final String filePath) throws IOException {
File file = new File(filePath);
InputStream is = new FileInputStream(file);
String result = read(is);
is.close();
return result;
}

/**
* 从一个输入流中读取文件内容.
*
* @param is
*            InputStream object
* @return String The content in the InputSream.
* @throws IOException
*/
public static String read(InputStream is) throws IOException {
BufferedInputStream bis = new BufferedInputStream(is);
StringBuffer buf = new StringBuffer();
int size = 0;
while ((size = bis.available()) > 0) {
byte[] temp = new byte[size];
bis.read(temp);
buf.append(new String(temp));
}
return buf.toString();
}

/**
* 保存字符串到指定的文件.
*
* @param filePath
*            文件路径,包括文件名
* @param content
*            文件内容
* @throws IOException
*/
public static void save(final String filePath, final String content)
throws IOException {
File file = new File(filePath);
OutputStream os = new FileOutputStream(file);
save(os, content);
os.close();
}

/**
* 保存字符串到输出流中.
*
* @param os
*            输出流
* @param content
*            内容
* @throws IOException
*/
public static void save(final OutputStream os, final String content)
throws IOException {
BufferedOutputStream bos = new BufferedOutputStream(os);
bos.write(content.getBytes());
bos.flush();
}

/**
* 得到java class存放的目录
*
* @return String
*/
public static String getRealClassRootPath() {
URI uri = null;
try {
uri = FileUtil.class.getResource("FileUtil.class").toURI();
} catch (URISyntaxException e1) {
// TODO
}
// String scheme = uri.getScheme();
String path = uri.getPath();
int index = path.indexOf("/com/");
if (index == -1) {
index = path.indexOf("classes") + "classes".length();
}
path = path.substring(0, index);
return path;
}

private static Properties prop = System.getProperties();
private static String os = prop.getProperty("os.name");
private static boolean isWin = os.toUpperCase().startsWith("WIN");


/**
* 将本地文件写到统一文件系统
*
* @param localFileName
*            诚寻运行本地系统文件路径
* @return 统一文件系统分配的文件名， 失败返回null
*/
public static String writeFile(String localFileName) {
String rFileName = System.currentTimeMillis() + "";
String dirName;
if(isWin) {
dirName = "c:\\temp\\";
}
else {
dirName = "/tmp/";
}

try {
File localFile = new File(localFileName);
InputStream is = new FileInputStream(localFile);
BufferedInputStream bis = new BufferedInputStream(is);
File dirFile = new File(dirName);
if(dirFile.isFile()) {
dirFile.delete();
}
if(!dirFile.exists()) {
dirFile.mkdir();
}
rFileName = dirName + rFileName;
File rFile = new File(rFileName);
OutputStream os = new FileOutputStream(rFile);
BufferedOutputStream bos = new BufferedOutputStream(os);
int size = 0;
while ((size = bis.available()) > 0) {
byte[] temp = new byte[size];
bis.read(temp);
bos.write(temp);
}
bos.flush();
bos.close();
os.close();
bis.close();
is.close();
System.out.println("rFileName is " + rFileName);
return rFileName;
} catch (Exception ex) {
ex.printStackTrace();
return null;
}

}

/**
* 将二进制流写到统一文件系统
*
* @param fileContent
* @return 统一文件系统分配的文件名， 失败返回null
*/
public static String writeFile(byte[] fileContent) {
String rFileName = System.currentTimeMillis() + "";
String dirName;
if(isWin) {
dirName = "c:\\temp\\";
}
else {
dirName = "/tmp/";
}

try {
File dirFile = new File(dirName);
if(dirFile.isFile()) {
dirFile.delete();
}
if(!dirFile.exists()) {
dirFile.mkdir();
}
rFileName = dirName + rFileName;
File file = new File(rFileName);
OutputStream os = new FileOutputStream(file);
os.write(fileContent);
os.flush();
os.close();
System.out.println("rFileName is " + rFileName);
return rFileName;
} catch (Exception ex) {
ex.printStackTrace();
return null;
}
}

/**
* 将统一文件系统读到本地文件中, 如果本地文件已经存在， 会先被删除
*
* @param rfileName
*            写文件时返回的文件名
* @param localFileName
*            本地文件路径
* @return 成功 true, 失败 false
*/
public static boolean readFile(String rfileName, String localFileName) {
try {
File file = new File(localFileName);
if (file.exists()) {
file.delete();
}
file.createNewFile();
File rFile = new File(rfileName);
InputStream is = new FileInputStream(rFile);
BufferedInputStream bis = new BufferedInputStream(is);
File localFile = new File(localFileName);
OutputStream os = new FileOutputStream(localFile);
BufferedOutputStream bos = new BufferedOutputStream(os);
int size = 0;
while ((size = bis.available()) > 0) {
byte[] temp = new byte[size];
bis.read(temp);
bos.write(temp);
}
bos.flush();
bos.close();
os.close();
bis.close();
is.close();
return true;
} catch (Exception ex) {
ex.printStackTrace();
return false;
}
}

/**
* 将统一文件系统读到输出流中
*
* @param rfileName
*            写文件时返回的文件名
* @param output
*            输出流
* @return 成功 true, 失败 false
*/
public static boolean readFile(String rfileName, OutputStream output) {
try {
File rFile = new File(rfileName);
InputStream is = new FileInputStream(rFile);
BufferedInputStream bis = new BufferedInputStream(is);
int size = 0;
while ((size = bis.available()) > 0) {
byte[] temp = new byte[size];
bis.read(temp);
output.write(temp);
}
output.flush();
output.close();
bis.close();
is.close();
return true;
} catch (Exception ex) {
ex.printStackTrace();
return false;
}
}

public static boolean readFile(String rfileName, List<String> fileContents, String charsetName) {
try {
File rFile = new File(rfileName);
InputStream is = new FileInputStream(rFile);
BufferedInputStream bis = new BufferedInputStream(is);
InputStreamReader inReader = new InputStreamReader(bis, charsetName);
BufferedReader bufferReader = new BufferedReader(inReader);
if(fileContents == null) {
fileContents = new ArrayList<String>();
}
while(bufferReader.ready()) {
fileContents.add(bufferReader.readLine());
}
is.close();
bis.close();
inReader.close();
bufferReader.close();
return true;
} catch (Exception ex) {
ex.printStackTrace();
return false;
}
}

/**
* 在统一文件系统中删除文件
*
* @param rfileName
*            写文件时返回的文件名
* @return 成功 true, 失败 false
*/
public static boolean deleteFile(String rfileName) {
File file = new File(rfileName);
return file.delete();
}