Java第十天笔记01—

1.File类

2.流的概念及API

3.字节输入流

4.字节输出流

5.使用字节输入和字节输出流复制文件

6.字符输入流

7. 字符输出流

8.字符输入和字符输出流复制文件内容

9.使用处理流复制文件内容

1.File类

（1）常见构造方法

①File 变量名 = new File(String pathname);

②File 变量名 = new File(URI uri);

③File 变量名 = new File(String parent, String child);

④File 变量名 = new File(File parent, String child);

（2）常见方法

（3）例子

package test;import java.io.File;
import java.io.IOException;public class Test {public static void main(String[] args) {File file = new File("D:" + File.separator + "temp2" + File.separator + "a.txt");//File.separator代表文件中的斜线“\”//相当于File file2 = new File("D:\\temp2\\a.txt");File file3 = new File("b.txt");File parent = new File("D:\\temp2");File file4 = new File(parent, "c.txt");File file5 = new File("D:\\temp2", "d.txt");if(!file2.exists()){//file2不存在try {parent.mkdir();//创建文件夹file2.createNewFile();//创建file2文件} catch (IOException e) {e.printStackTrace();}}System.out.println(file3.getAbsolutePath());//输出绝对路径File files = new File("D:\\temp2\\test\\a");files.mkdirs();//创建多级目录}
}

2.流的概念及API

（1）流的概念

流（Stream )的概念代表的是程序中数据的流通
数据流是一串连续不断的数据的集合
在Java程序中，对于数据的输入/输出操作是以流(Stream)的方式进行的

（2）流的分类
①按流的方向不同
输入流、输出流
②按处理数据的单位不同
字节流、字符流
③按功能不同
节点流、处理流

3.字节输入流

（1）InputStream常用的方法

（2）例子

读取“D:\temp2”目录下a.txt文件的内容

package test;import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;public class InputStreamTest {/** 一个一个字节读取    */public static void method1(){File directory = new File("D:\\temp2");File file = new File(directory, "a.txt");InputStream is = null;//创建字节输入流对象try {is = new FileInputStream(file);System.out.println(is.read());System.out.println(is.read());System.out.println(is.read());System.out.println(is.read());System.out.println(is.read());System.out.println(is.read());System.out.println(is.read());//............} catch (Exception e) {e.printStackTrace();} finally{try {is.close();//释放流占用的资源} catch (IOException e) {e.printStackTrace();}}}/** 多个字节读取   */public static void method2(){File directory = new File("D:\\temp2");File file = new File(directory, "a.txt");InputStream is = null;//创建字节输入流对象try {is = new FileInputStream(file);byte[] b = new byte[5];//开房间存放读取的数据，这是数据的中转站，也叫做缓冲区int num = 0;//用于记录每次读取到的字节数量while((num = is.read(b)) != -1){System.out.println(new String(b, 0, num));//打印读到的结果}} catch (Exception e) {e.printStackTrace();} finally{try {is.close();//释放流占用的资源} catch (IOException e) {e.printStackTrace();}}}public static void main(String[] args) {method1();method2();}
}

4.字节输出流

（1）OutputStream常用的方法

（2）例子

给“D:\temp2”目录下b.txt文件写入内容

package test;import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;public class OutputSreamTest {/** 一个一个字节写入b.txt */public static void method1(){File directory = new File("D:\\temp2");File file = new File(directory, "b.txt");OutputStream os = null;//创建字节输出流try {os = new FileOutputStream(file);os.write(97);//aos.write(98);//bos.write(99);//cos.write(100);//dos.write(101);//e//......} catch (Exception e) {e.printStackTrace();} finally{try {os.close();释放流占用的资源} catch (IOException e) {e.printStackTrace();}}}/** 多个字节写入b.txt  */public static void method2(){File directory = new File("D:\\temp2");File file = new File(directory, "b.txt");OutputStream os = null;//创建字节输出流try {os = new FileOutputStream(file);byte[] b = new byte[]{'A', 'B', 'C', 'D', 'E'};os.write(b);} catch (Exception e) {e.printStackTrace();} finally{try {os.close();释放流占用的资源} catch (IOException e) {e.printStackTrace();}}}public static void main(String[] args) {method1();method2();}
}

5.使用字节输入和字节输出流复制文件

将“D:\temp2\a.txt”文件的内容复制到“D:\temp2\b.txt”

package test;import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;public class CopyFileContent1 {public static void main(String[] args) {File directory = new File("D:\\temp2");File src = new File(directory, "a.txt");// 源文件File dest = new File(directory, "b.txt");// 目标文件InputStream is = null;// 创建字节输入流对象OutputStream os = null;// 创建字节输出流对象try {is = new FileInputStream(src);os = new FileOutputStream(dest);byte[] b = new byte[5];// 开房间存放读取的数据，这是数据的中转站，也叫做缓冲区int num = 0;// 用于记录每次读取到的字节数量while ((num = is.read(b)) != -1) {os.write(b, 0, num);// 将从a.txt文件中读取到的字节写入b.txt}} catch (Exception e) {e.printStackTrace();} finally {try {is.close();// 释放流占用的资源} catch (IOException e) {e.printStackTrace();}}}
}

6.字符输入流

（1）Reader常用的方法

（2）例子

读取“D:\temp2”目录下a.txt文件的内容

package test;import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;public class ReaderTest {/** 一个一个字符读取  */public static void method1(){File directory = new File("D:\\temp2");File file = new File(directory, "a.txt");Reader reader = null;try {reader = new FileReader(file);System.out.println((char)reader.read());System.out.println((char)reader.read());System.out.println((char)reader.read());System.out.println((char)reader.read());System.out.println((char)reader.read());//......} catch (Exception e) {e.printStackTrace();} finally{try {reader.close();//关闭字符流占用的资源} catch (IOException e) {e.printStackTrace();}}}/** 多个字符读取  */public static void method2(){File directory = new File("D:\\temp2");File file = new File(directory, "a.txt");Reader reader = null;try {reader = new FileReader(file);char[] cbuf = new char[5];int num = 0;while((num = reader.read(cbuf)) != -1){System.out.println(new String(cbuf, 0, num));}} catch (Exception e) {e.printStackTrace();} finally{try {reader.close();//关闭字符流占用的资源} catch (IOException e) {e.printStackTrace();}}}public static void main(String[] args) {method1();method2();}
}

7. 字符输出流

（1）Writer常用的方法

（2）例子

给“D:\temp2”目录下b.txt文件写入内容

package test;import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;public class WriterTest {/** 一个一个字符写入  */public static void method1(){File directory = new File("D:\\temp2");File file = new File(directory, "b.txt");Writer writer = null;try {writer = new FileWriter(file);writer.write(65);writer.write(66);writer.write(67);writer.write(68);writer.write(69);writer.write(70);//......} catch (IOException e) {e.printStackTrace();} finally{try {writer.close();//释放字符输出流占用的资源} catch (IOException e) {e.printStackTrace();}}}/** 多个字符写入    */public static void method2(){File directory = new File("D:\\temp2");File file = new File(directory, "b.txt");Writer writer = null;try {writer = new FileWriter(file);char[] cbuf = {'A', 'B', 'C', 'D', 'E', 'F'};writer.write(cbuf);} catch (IOException e) {e.printStackTrace();} finally{try {writer.close();//释放字符输出流占用的资源} catch (IOException e) {e.printStackTrace();}}}public static void main(String[] args) {method1();method2();}
}

8.字符输入和字符输出流复制文件内容

将“D:\temp2\a.txt”文件的内容复制到“D:\temp2\b.txt”

package test;import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Reader;
import java.io.Writer;public class CopyFileContent2 {public static void main(String[] args) {File directory = new File("D:\\temp2");File src = new File(directory, "a.txt");File dest = new File(directory, "b.txt");Reader reader = null;Writer writer = null;try {reader = new FileReader(src);writer = new FileWriter(dest);char[] cbuf = new char[5];int num = 0;while((num = reader.read(cbuf)) != -1){writer.write(cbuf, 0, num);}} catch (Exception e) {e.printStackTrace();} finally{try {reader.close();//关闭字符流占用的资源writer.close();} catch (IOException e) {e.printStackTrace();}}}
}

9.使用处理流复制文件内容

package test;import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Reader;
import java.io.Writer;public class CopyFileContent3 {public static void main(String[] args) {File directory = new File("D:\\temp2");File src = new File(directory, "a.txt");File dest = new File(directory, "b.txt");BufferedReader reader = null;// 创建缓冲字符输入流BufferedWriter writer = null;// 创建缓冲字符输出流Reader read = null;// 创建字符输入流Writer write = null;// 创建字符输出流try {read = new FileReader(src);write = new FileWriter(dest);reader = new BufferedReader(read);writer = new BufferedWriter(write);int num = 0;char[] cbuf = new char[5];while ((num = reader.read(cbuf)) != -1) {writer.write(cbuf, 0, num);writer.flush();// 刷新}} catch (Exception e) {e.printStackTrace();} finally {try {read.close();reader.close();write.close();writer.close();} catch (IOException e) {e.printStackTrace();}}}
}

自动资源管理
在JDK 7之前，我们需要使用一个finally块，来确保资源确实被释放掉，不管try块是完成了还是中断了。比如说读取文件或者输入流的时候，我们需要在finally块中关闭它们；而在Java 7里面，你可以使用try-with-resource的特性来自动关闭资源，只要是实现了AutoClosable和Closeable接口的都可以，几乎所有的资源类型都实现了Closeable接口，并重写了close()方法。JDK 7引入了try-with-resource语句，来确保每个资源在语句结束后都会调用AutoClosable接口的close()方法进行关闭。

例子：

package test;import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.Reader;
import java.io.Writer;public class CopyFileContent3 {public static void main(String[] args) {File directory = new File("D:\\temp2");File src = new File(directory, "a.txt");File dest = new File(directory, "b.txt");try (Reader read = new FileReader(src);BufferedReader reader = new BufferedReader(read);Writer write = new FileWriter(dest);BufferedWriter writer = new BufferedWriter(write);) {int num = 0;char[] cbuf = new char[5];while ((num = reader.read(cbuf)) != -1) {writer.write(cbuf, 0, num);writer.flush();// 刷新}} catch (Exception e) {e.printStackTrace();}}
}