io

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package com.knock0801am.IOtest;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import java.io.InputStream;/** * IO 类有很多，只关注重点 * 分类：输入流；输出流 * 字节流；字符流 * 节点流；处理流 *  * 四个基本的抽象类：IuputStream;OutputStream;Reader;Writer *  * 常用的实现类：FileInputStream; * */public class TestIORead {/*四个步骤：1选择源2选择流3操作，如定义byte[]+ read +close4结束，释放资源*/public static void main(String[] args) {File file = new File("D:/test/a.txt");InputStream is  = null;try {is  = new FileInputStream(file);byte[] resource = new byte[1024];int len = 0;/*read方法有三个重载，包括：read();每次只读一个字节，效率很低read(byte[] resource);每次读一个数组长度的字节resd(byte[] resource,offset,resourcelength);每次读一个实际获得的数组的字节(从0开始读，读到数组内容结尾)（推荐）*/while(-1!= (len=is.read(resource))){//构建字符串，然后把他输出String str = new String(resource,0,len);System.out.println(str);}} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally{try {is.close();} catch (IOException e) {e.printStackTrace();}}}}

<pre name="code" class="java">package com.knock0801am.IOtest;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.OutputStream;/** * 四个基本步骤 * 输出流需要多留意一个方法：flush() *  * */public class TestIOWrite {/*四个步骤：1选择源2选择流3操作，如定义byte[]+ read +close4结束，释放资源*/public static void main(String[] args) {OutputStream os = null;try {/*注意输出流这里跟输入流稍有不同，除了有File参数和路径字符串参数以外，输出流还可以带一个boolean类型的参数，默认为false，表示覆盖；如果为true，则为追加*/os = new FileOutputStream("E:/test/a.txt",true);/*把字符串转化为字符数组，然乎输出到文件中*/String str ="锄禾日当午，码农真辛苦，一本小破书，一读一上午";byte[] byteStr = str.getBytes();int len = 0 ;os.write(byteStr, 0, byteStr.length);//跟输入流不一样，不需要定义一个数组来确定每次输出的大小，一次全部输出，但是需要flush();os.flush();} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally{try {os.close();} catch (IOException e) {e.printStackTrace();}}}}

package com.knock0801am.IOtest;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;/** * 把输入输出结合起来，完成文件拷贝：从D拷贝到E *  * */public class CopyFile {public static void main(String[] args) {InputStream is = null;OutputStream os = null;try {is = new FileInputStream("D:/test/1.jpg");os = new FileOutputStream("E:/test/100.jpg");byte[] resource = new byte[1024];int len = 0;while(-1 != (len = is.read(resource))){os.write(resource, 0, len);}os.flush();} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally{try {if(null!=os){os.close();}if(null!=is){is.close();}} catch (IOException e) {e.printStackTrace();}}}}

package com.knock0801am.IOtest;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;/** * 稍微封装一下 * */public class CopyFile2 {public static void copyFile(FileInputStream fis,FileOutputStream fos){InputStream is = null;OutputStream os = null;try {is = fis;os = fos;byte[] resource = new byte[1024];int len = 0;while(-1 != (len = is.read(resource))){os.write(resource, 0, len);}os.flush();} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally{try {if(null!=os){os.close();}if(null!=is){is.close();}} catch (IOException e) {e.printStackTrace();}}}}

package com.knock0801am.IOtest;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;public class Test {public static void main(String[] args) {try {FileInputStream fis = new FileInputStream("D:/test/1.jpg");FileOutputStream fos = new FileOutputStream("E:/test/100.jpg");CopyFile2.copyFile(fis, fos);} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}

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