IO流的分类举例
作者：互联网
一、FileInputStream
| 方法 | 说明 |
| int available() | 返回可以从该输入流不阻塞地读取(或跳过)的字节数的估计值，该值可能为0，或当检测到流的结束时为0 |
| int read() | 向流中写一个字符 |
| int read(byte[] b) | 将多个字节读到 b 数组中 |
| int read(byte[] b, int off, int len) | 读取流中的多个字节并填充到数组中指定位置中 |
| void reset() | 重置流 |
| log skip(long n) | 跳过多个字符 |
| void close() | 关闭流 |
public class TestFile {
public static void main(String[] args) {
//读取temp.txt文件内容
//流使用后 一定要关闭！！！写在finally中
FileInputStream fis = null;
try {
fis = new FileInputStream("D:\\Lession\\Java2113\\temp.txt");
int temp = 0;
while((temp = fis.read())!=-1) {
System.out.println(temp);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}read(byte[ ] b) : 读取内容到byte[ ]中，结果是读取字节的个数，如果没有读取到字节返回-1
public static void main(String[] args) {
//读哪个文件
FileInputStream fis = null;
/*File file = new File("D:\\Lession\\Java2113\\temp.txt");
try {
fis = new FileInputStream(file);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}*/
try {
fis = new FileInputStream("D:\\Lession\\Java2113\\temp.txt");
//读取一个字节，返回字节的unicode值
//fis.read();
//读取到byte[]中，返回读取的长度
//fis.read(byte[] b);
//读取到byte[]中，指定byte数组的位置
//fis.read(byte[] b, int off, int len)
/* System.out.println((char)fis.read());
System.out.println(fis.read());
System.out.println(fis.read());
System.out.println(fis.read());
System.out.println(fis.read()); //-1
*/ /*int temp = 0;
while((temp=fis.read())!=-1) {
System.out.println((char)temp);
}*/
//缓冲区
byte[] bytes = new byte[10];
int temp = 0;
while((temp=fis.read(bytes))!=-1) {
for(int i = 0;i<temp;i++) {
System.out.println((char)bytes[i]);
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}缓冲：如同生活中，将书从一个教室搬往另一个教室，若一本一本地去搬会很慢，也很累，例如int read()方法的使用；
而如果有一个书包作为搬运工具，将教室里的书装到书包中进行搬运会较快，有一个向书包中装书的缓冲过程，例如，int read(byte[ ] b)方法的使用
读中文
public static void main(String[] args) {
FileInputStream fis = null;
try {
fis = new FileInputStream("D:\\Lession\\Java2113\\temp.txt");
byte[] bytes = new byte[fis.available()];
int temp = 0;
if((temp=fis.read(bytes))!=-1) {
System.out.println(new String(bytes,"UTF-8"));
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}二、FileOutputStream
| 方法 | 说明 |
| void write(byte b) | 向流中写一个字节 |
| void write(byte[] str) | 向流中写一个字节数组 |
| void write(byte[] b, int off, int len) | 向流中写入字节数组的一部分 |
| void flush() | 刷新流 |
| void close() | 关闭流 |
构造器：
FileOutputStream(File file) 默认从开头新加内容，覆盖。
FileOutputStream(File file,boolean append) 从末尾追加内容
public class TestFileOutputStream {
public static void main(String[] args) {
//向temp.txt中写 abcd
FileOutputStream fos = null;
try {
fos = new FileOutputStream("D:\\Lession\\Java2113\\temp.txt");
fos.write("阿伯测的".getBytes());
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}应用：将一个文件复制到另一个文件
public static void copy1(String srcPath,String destPath) {
FileInputStream fis = null;
FileOutputStream fos = null;
byte[] bytes = new byte[1024];
try {
fis = new FileInputStream(srcPath);
fos = new FileOutputStream(destPath);
int temp = 0;
while ((temp = fis.read(bytes)) != -1) {
fos.write(bytes, 0, temp);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}三、BufferedInputStream/BufferedOutputStream
•此流是一个处理流，是一个带缓冲区的字节输出流。 •BufferedOutputStream 可以减少IO次数。public static void copy2(String srcPath,String destPath) {
FileInputStream fis = null;
FileOutputStream fos = null;
BufferedInputStream bis = null;
BufferedOutputStream bos = null;
try {
fis = new FileInputStream(srcPath);
fos = new FileOutputStream(destPath);
bis = new BufferedInputStream(fis);
bos = new BufferedOutputStream(fos,1024);
int temp = 0;
while((temp=bis.read())!=-1) {
//缓冲流 默认是缓冲区满时，向设备输出
bos.write(temp);
}
//手动冲刷缓冲区向设备输出
bos.flush();//冲刷，将最后不足1024的部分进行读取
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally {
try {
bis.close();
} catch (IOException e1) {
e1.printStackTrace();
}
try {
bos.close();
} catch (IOException e1) {
e1.printStackTrace();
}
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}最后需要flush一下！！！
四、FileReader和FileWriter
Reader和Writer的子类，都是字符流
public class TestFileReader {
public static void main(String[] args) {
FileReader fr = null;
try {
fr = new FileReader("D:\\Lession\\Java2113\\temp1.txt");
int temp = 0;
char[] chars = new char[2];
while((temp=fr.read(chars))!=-1) {
for(char c:chars) {
System.out.println(c);
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}public class TestFileWriter {
public static void main(String[] args) {
try {
FileWriter fw = new FileWriter("D:\\Lession\\Java2113\\temp1.txt");
fw.write("你好中国");
fw.flush();
} catch (IOException e) {
e.printStackTrace();
}
}
}
五、BufferedReader 和 BufferedWriter
BufferedReader 提供了按行读的功能
BufferedWriter 提供了自定义缓冲区大小的功能
FileReader fr = null;
try {
fr = new FileReader("D:\\Lession\\Java2113\\temp1.txt");
BufferedReader br = new BufferedReader(fr);
String str = null;
while((str=br.readLine())!=null) {
System.out.println(str);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
FileWriter fw = new FileWriter("D:\\Lession\\Java2113\\temp1.txt");
BufferedWriter br = new BufferedWriter(fw,1024);
br.write("你好北京");
br.flush();
} catch (IOException e) {
e.printStackTrace();
}六、InputStreamReader和OutputStreamWriter （转换流）
都是字符流 继承于Reader和Writer , 是字节流转成字符流的桥梁
public static void main(String[] args) {
try {
FileInputStream fis = new FileInputStream("D:\\Lession\\Java2113\\temp.txt");
InputStreamReader reader = new InputStreamReader(fis,"UTF-8");
int temp = 0;
while((temp=reader.read())!=-1) {
System.out.println((char)temp);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}public static void main(String[] args) {
try {
FileOutputStream fos = new FileOutputStream("D:\\Lession\\Java2113\\temp1.txt");
/*fos.write("你好北京".getBytes());*/
OutputStreamWriter osw = new OutputStreamWriter(fos);
osw.write("你好北京");
osw.flush();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}七、PrintWriter
public static void main(String[] args) {
PrintWriter pw = null;
try {
FileOutputStream fos = new FileOutputStream("D:\\Lession\\Java2113\\temp1.txt");
pw = new PrintWriter(fos,true);
pw.println("你好北京");
pw.println("你好冬奥会");
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}八、DataInputStream和DataOutputStream
读写数据(基本类型数据)的字节流
try {
FileOutputStream fos = new FileOutputStream("D:\\Lession\\Java2113\\temp1.txt");
DataOutputStream dos = new DataOutputStream(fos);
dos.writeInt(1);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
public static void main(String[] args) {
try {
FileInputStream fis = new FileInputStream("D:\\Lession\\Java2113\\temp1.txt");
DataInputStream dis = new DataInputStream(fis);
System.out.println(dis.readInt());
} catch (IOException e) {
e.printStackTrace();
}
}标签：fis,temp,分类,try,printStackTrace,举例,IO,catch,new 来源： https://blog.csdn.net/aigo_2021/article/details/122869895