1、读文件:
readLine()是BufferedReader类的一个方法,它每次从缓冲里读一行数据。
BufferedReader类参数可为:InputStreamReader、FileReader类型
FileReader(File file)
FileReader(String fileName)
InputStreamReader(InputStream in)
//接收键盘输入作为输入流,把输入流放到缓冲流里面
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
BufferReader in=new BufferReader(new FileReader(name))
请编写一个字符输入流的包装类,通过这个包装类对底层字符输入流进行包装,让程序通过这个包装类读取某个文本文件(例如,一个java源文件)时,能够在读取的每行前面都加上有行号和冒号。
Java代码
void doPack(String fileNameAndPath)
{
FileReader fr;
try {
fr=new FileReader(fileNameAndPath);
BufferedReader br=new BufferedReader(fr);
String readLine=null;
int lineNumber=1;
while((readLine=br.readLine())!=null)
{
readLine=lineNumber+":"+readLine;
System.out.println(readLine);
lineNumber++;
}
} catch (Exception e) {
e.printStackTrace();
}
}
void doPack(String fileNameAndPath)
{
FileReader fr;
try {
fr=new FileReader(fileNameAndPath);
BufferedReader br=new BufferedReader(fr);
String readLine=null;
int lineNumber=1;
while((readLine=br.readLine())!=null)
{
readLine=lineNumber+":"+readLine;
System.out.println(readLine);
lineNumber++;
}
} catch (Exception e) {
e.printStackTrace();
}
} 易错地方:
Java代码
while(br.readLine()!=null){
System.out.println(br.readLine());
}
其中每个循环(一次打印)br.readLine()被执行了两次,当然是隔行打印!!.
应该是
BufferedReader br=new BufferedReader(file);
String line = null;
while((line = br.readLine()) != null){
System.out.println(line);
}
while(br.readLine()!=null){
System.out.println(br.readLine());
}
其中每个循环(一次打印)br.readLine()被执行了两次,当然是隔行打印!!.
应该是
BufferedReader br=new BufferedReader(file);
String line = null;
while((line = br.readLine()) != null){
System.out.println(line);
} 2、写文件:
BufferWriter(Writer out)
BufferWriter的参数类型可为:FileWriter、OutputStreamWriter
FileWriter(String fileName)
FileWriter(File file)
OutputStreamWriter(OutputStream out)
1、
Java代码
File file = new File(“D:\\abc.txt“);
FileWriter fw = new FileWriter("f:/jackie.txt");//创建FileWriter对象,用来写入字符流
BufferedWriter output = new BufferedWriter(fw);
output.write(s1);
File file = new File(“D:\\abc.txt“);
FileWriter fw = new FileWriter("f:/jackie.txt");//创建FileWriter对象,用来写入字符流
BufferedWriter output = new BufferedWriter(fw);
output.write(s1);
2.
Java代码
Writer out
= new BufferedWriter(new OutputStreamWriter(System.out));
Writer out
= new BufferedWriter(new OutputStreamWriter(System.out));
3、
Java代码
FileOutputStream fo = new FileOutputStream(filePath);
OutputStreamWriter out = new OutputStreamWriter(fo, "UTF-8");
out.write(fileContent);
out.close();
FileOutputStream fo = new FileOutputStream(filePath);
OutputStreamWriter out = new OutputStreamWriter(fo, "UTF-8");
out.write(fileContent);
out.close();
其他:
FileOutputStream 用于写入诸如图像数据之类的原始字节的流。
FileWriter只能写文本文件
InputStream in = new BufferedInputStream( new FileInputStream(filePath));
例子:
Java代码
private void copy(File src, File dst) {
InputStream in = null;
OutputStream out = null;
try {
in = new BufferedInputStream(new FileInputStream(src), BUFFER_SIZE);
out = new BufferedOutputStream(new FileOutputStream(dst), BUFFER_SIZE);
byte[] buffer = new byte[BUFFER_SIZE];
int len = 0;
while ((len = in.read(buffer)) > 0) {
out.write(buffer, 0, len);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (null != in) {
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (null != out) {
try {
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
private void copy(File src, File dst) {
InputStream in = null;
OutputStream out = null;
try {
in = new BufferedInputStream(new FileInputStream(src), BUFFER_SIZE);
out = new BufferedOutputStream(new FileOutputStream(dst), BUFFER_SIZE);
byte[] buffer = new byte[BUFFER_SIZE];
int len = 0;
while ((len = in.read(buffer)) > 0) {
out.write(buffer, 0, len);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (null != in) {
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (null != out) {
try {
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
} Java代码
/* Reads some number of bytes from the input stream and stores them into
* the buffer array <code>b</code>. The number of bytes actually read is
* returned as an integer.
*/
public int read(byte b[])
*
* Writes <code>len</code> bytes from the specified byte array
* starting at offset <code>off</code> to this output stream.
*/
ublic void write(byte b[], int off, int len)
/* Reads some number of bytes from the input stream and stores them into
* the buffer array <code>b</code>. The number of bytes actually read is
* returned as an integer.
*/
public int read(byte b[])
/*
* Writes <code>len</code> bytes from the specified byte array
* starting at offset <code>off</code> to this output stream.
*/
public void write(byte b[], int off, int len) 。。。
InputStream转byte[]:
Java代码
private byte[] InputStreamToByte(InputStream is) throws IOException {
ByteArrayOutputStream bytestream = new ByteArrayOutputStream();
int ch;
while ((ch = is.read()) != -1) {
bytestream.write(ch);
}
byte bb[] = bytestream.toByteArray();
bytestream.close();
return bb;
}
private byte[] InputStreamToByte(InputStream is) throws IOException {
ByteArrayOutputStream bytestream = new ByteArrayOutputStream();
int ch;
while ((ch = is.read()) != -1) {
bytestream.write(ch);
}
byte bb[] = bytestream.toByteArray();
bytestream.close();
return bb;
}
byte[] 转InputStream
Java代码
byte[] data;
InputStream is = new ByteArrayInputStream(data);
byte[] data;
InputStream is = new ByteArrayInputStream(data);
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