Java中的文件输入输出流

最近学习了如何读取输出文件，贴上部分代码：

TestInputStream1():

String strFile = "Data/DataGroup.cpp";

File = new File(strFile);

InputStream in = null;

in = new FileInputStream(file);

//创建合适文件大小的数组,一次性把数据从文件中读出

b1 = new byte[(int)file.length()];

// 读取文件中的内容到b[]数组，如果read()返回读取的字节内容，

// 当内容为空时返回-1，可以以此作为判断文件内容是否读取完毕

in.read(b1);

in.close();

textArea.append(new String(b1));

TestInputStream2():

int iSize = 1024;

boolean blSleep = true;

String strFile = "Data/DataGroup.cpp";

File file = new File(strFile);

int iCount = (int)file.length()/iSize;

InputStream in = null;

in = new FileInputStream(file);

b2 =new byte[iSize];

int temp = 0;

int no = 0;

while((temp = in.read()) != -1){

no++;

in.read(b2);

System.out.PRintln(new String(b2));

if(no < iCount){

in.read(b2);

System.out.println(new String(b2));

}

else{

blSleep = false;

System.out.print((char)temp);

}

}

in.close();

执行TestInputStream1()，后：

TestOutputStream(): （读文本文件，然后显示到组件，写到另外一个文件）

// 写文件时的相关变量

String strOut = "*Data/DataGroup_copy.cpp";

File file = new File(strOut);

OutputStream output = null;

output = new FileOutputStream(file);

output.write(b1);

output.close();

TestPrintStream()://读取并输出屏幕上，输出到文件上

String strFile = "Data/DataGroup.cpp";

File file = new File(strFile);

InputStream in = null;

in = new FileInputStream(file);

//创建合适文件大小的数组,一次性把数据从文件中读出

b1 = new byte[(int)file.length()];

// 读取文件中的内容到b[]数组，如果read()返回读取的字节内容，

// 当内容为空时返回-1，可以以此作为判断文件内容是否读取完毕

in.read(b1);

in.close();

// 将数据输出到屏幕

PrintStream printStream = new PrintStream(System.out);

printStream.println(new String(b1));

printStream.flush(); // 彻底完成输出并清空缓冲区

printStream.close();

// 将数据输出到文件

File filePrint = new File("Data/print.cpp");

printStream = new PrintStream(filePrint);

printStream.println(new String(b1));

printStream.close();

TestDataInputStream()：

// 键盘输入(如何自适应根据用户输入的数据多少分配空间)

byte b[] = new byte[12];

DataInputStream dataInputStream = new DataInputStream(System.in);

String str = null;

dataInputStream.read(b);

dataInputStream.close();

System.out.println(new String(b));

// 文件输入

String strFile = "Data/表2-5.txt";

byte byFile[] = null;

File file = new File(strFile);

InputStream instream = null;

instream = new FileInputStream(file);

dataInputStream = new DataInputStream(instream);

float temp = (float) 0.0;

str = null;

byFile = new byte[(int)file.length()];

dataInputStream.read(byFile);

dataInputStream.close();

System.out.println(new String(byFile));

TestDataInputStream2()：//二进制

System.out.println("从文件中每次读取一个数值");

DataInputStream dataInputStream = null;

// 文件输入

String strFile = "Data/表2-5_Copy.txt";

File file = new File(strFile);

InputStream instream = null;

instream = new FileInputStream(file);

dataInputStream = new DataInputStream(instream);

System.out.println("二进制文件读取结果的输出!");

float temp = (float) 0.0;

// 判断是否文件结束

while(dataInputStream.available() > 0){

temp = dataInputStream.readFloat();

System.out.println(temp);

instream.close();

dataInputStream.close();

TestDataOutputStream()：

DataOutputStream outputStream = null;

DataInputStream inputStream = null;

// 文件输入

byte byFile[] = null;

File file = new File("Data/表2-5.txt");

InputStream instream = null;

instream = new FileInputStream(file);

inputStream = new DataInputStream(instream);

String str = null;

byFile = new byte[(int)file.length()];

inputStream.read(byFile);

str = new String(byFile);

inputStream.close();

String strSplit[] = str.split(" ");

System.out.println(strSplit.length);

// 把字符串str中的数据一个一个写入文件中(二进制格式文件)

String strFile = "Data/表2-5_Copy.txt";

file = new File(strFile);

OutputStream out = null;

out = new FileOutputStream(file);

outputStream = new DataOutputStream(out);

for(int i = 0;i < strSplit.length;i++){

float temp = Float.valueOf(strSplit[i]);

System.out.println(temp);

outputStream.writeFloat(temp);

}

out.close();

outputStream.close();

}

TestBufferReaderAndBufferedWriter()：

// 键盘输入

InputStreamReader isr = new InputStreamReader(System.in);

BufferedReader br = new BufferedReader(isr) ;

String str = null;

str = br.readLine();

isr.close();

br.close();

System.out.println(str);

// 读文件

str = null;

String strFile = "Data/result_表2-5.txt";

if(isr != null) isr = null;

isr = new InputStreamReader(new FileInputStream(new File(strFile)));

br = new BufferedReader(isr);

// 写文件

String strWrite = "Data/result_表2-5_copy.txt";

OutputStreamWriter out = null;

BufferedWriter bw = null;

out = new OutputStreamWriter(new FileOutputStream(new File(strWrite)));

bw = new BufferedWriter(out);

// Java中有没有类似于rewind函数,即对指针进行重定位？？？？？？？？？

isr = new InputStreamReader(new FileInputStream(new File(strFile)));

br = new BufferedReader(isr);

str = null;

while((str = br.readLine()) != null){

System.out.println(str);

bw.write(str); // 在使用readLine读取时,换行符已经被取消

bw.newLine();

}

bw.close();

out.close();