javaSE第二十一天

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStreamReader;

?

/*

* InputStreamReader的方法：

* int read():一次读取一个字符

* int read(char[] chs):一次读取一个字符数组

*/

class InputStreamReaderDemo {

????public?static?void main(String[] args) throws IOException {

????????// 创建对象

????????InputStreamReader isr = new InputStreamReader(new FileInputStream(

????????????????"StringDemo.java"));

?

????????// 一次读取一个字符

????????// int?ch = 0;

????????// while ((ch = isr.read()) != -1) {

????????// System.out.print((char) ch);

????????// }

?

????????// 一次读取一个字符数组

????????char[] chs = new?char[1024];

????????int?len = 0;

????????while ((len = isr.read(chs)) != -1) {

????????????System.out.print(new String(chs, 0, len));

????????}

?

????????// 释放资源

????????isr.close();

????}

}

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.OutputStreamWriter;

?

/*

* OutputStreamWriter的方法：

* public void write(int c):写一个字符

* public void write(char[] cbuf):写一个字符数组

* public void write(char[] cbuf,int off,int?len):写一个字符数组的一部分

* public void write(String str):写一个字符串

* public void write(String str,int off,int?len):写一个字符串的一部分

*

* 面试题：close()和flush()的区别?

* A:close()关闭流对象，但是先刷新一次缓冲区。关闭之后，流对象不可以继续再使用了。

* B:flush()仅仅刷新缓冲区,刷新之后，流对象还可以继续使用。

*/

class OutputStreamWriterDemo {

????public?static?void main(String[] args) throws IOException {

????????// 创建对象

????????OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream(

????????????????"osw2.txt"));

?

????????// 写数据

????????// public void write(int c):写一个字符

????????// osw.write(‘a‘);

????????// osw.write(97);

????????// 为什么数据没有进去呢?

????????// 原因是：字符 = 2字节

????????// 文件中数据存储的基本单位是字节。

????????// void flush()

?

????????// public void write(char[] cbuf):写一个字符数组

????????// char[] chs = {‘a‘,‘b‘,‘c‘,‘d‘,‘e‘};

????????// osw.write(chs);

?

????????// public void write(char[] cbuf,int off,int?len):写一个字符数组的一部分

????????// osw.write(chs,1,3);

?

????????// public void write(String str):写一个字符串

????????// osw.write("我爱林青霞");

?

????????// public void write(String str,int off,int?len):写一个字符串的一部分

????????osw.write("我爱林青霞", 2, 3);

?

????????// 刷新缓冲区

????????osw.flush();

????????// osw.write("我爱林青霞", 2, 3);

?

????????// 释放资源

????????osw.close();

????????// java.io.IOException: Stream closed

????????// osw.write("我爱林青霞", 2, 3);

????}

}

import java.io.UnsupportedEncodingException;

import java.util.Arrays;

?

/*

* String(byte[] bytes, String charsetName):通过指定的字符集解码字节数组

* byte[] getBytes(String charsetName):使用指定的字符集合把字符串编码为字节数组

*

* 编码:把看得懂的变成看不懂的

* String -- byte[]

*

* 解码:把看不懂的变成看得懂的

* byte[] -- String

*

* 举例：谍战片(发电报，接电报)

*

* 码表：小本子

* ????????字符????数值

*

* 要发送一段文字：

* ????????今天晚上在老地方见

*

* ????????发送端：今 -- 数值 -- 二进制 -- 发出去

* ????????接收端：接收 -- 二进制 -- 十进制 -- 数值 -- 字符 -- 今

*

* ????????今天晚上在老地方见

*

* 编码问题简单，只要编码解码的格式是一致的。

*/

class StringDemo {

????public?static?void main(String[] args) throws UnsupportedEncodingException {

????????String s = "你好";

?

????????// String -- byte[]

????????byte[] bys = s.getBytes(); // [-60, -29, -70, -61]

????????// byte[] bys = s.getBytes("GBK");// [-60, -29, -70, -61]

????????// byte[] bys = s.getBytes("UTF-8");// [-28, -67, -96, -27, -91, -67]

????????System.out.println(Arrays.toString(bys));

?

????????// byte[] -- String

????????String ss = new String(bys); // 你好

????????// String ss = new String(bys, "GBK"); // 你好

????????// String ss = new String(bys, "UTF-8"); // ???

????????System.out.println(ss);

????}

}

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.OutputStreamWriter;

?

/*

* OutputStreamWriter(OutputStream out):根据默认编码把字节流的数据转换为字符流

* OutputStreamWriter(OutputStream out,String charsetName):根据指定编码把字节流数据转换为字符流

* 把字节流转换为字符流。

* 字符流 = 字节流 +编码表。

*/

class OutputStreamWriterDemo {

????public?static?void main(String[] args) throws IOException {

????????// 创建对象

????????// OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream(

????????// "osw.txt")); // 默认GBK

????????// OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream(

????????// "osw.txt"), "GBK"); // 指定GBK

????????OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream(

????????????????"osw.txt"), "UTF-8"); // 指定UTF-8

????????// 写数据

????????osw.write("中国");

?

????????// 释放资源

????????osw.close();

????}

}

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStreamReader;

?

/*

* InputStreamReader(InputStream is):用默认的编码读取数据

* InputStreamReader(InputStream is,String charsetName):用指定的编码读取数据

*/

class InputStreamReaderDemo {

????public?static?void main(String[] args) throws IOException {

????????// 创建对象

????????// InputStreamReader isr = new InputStreamReader(new FileInputStream(

????????// "osw.txt"));

?

????????// InputStreamReader isr = new InputStreamReader(new FileInputStream(

????????// "osw.txt"), "GBK");

?

????????InputStreamReader isr = new InputStreamReader(new FileInputStream(

????????????????"osw.txt"), "UTF-8");

?

????????// 读取数据

????????// 一次读取一个字符

????????int?ch = 0;

????????while ((ch = isr.read()) != -1) {

????????????System.out.print((char) ch);

????????}

?

????????// 释放资源

????????isr.close();

????}

}

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStreamReader;

import java.io.OutputStreamWriter;

?

/*

* 需求：把当前项目目录下的a.txt内容复制到当前项目目录下的b.txt中

*

* 数据源：

* ????????a.txt -- 读取数据 -- 字符转换流 -- InputStreamReader

* 目的地：

* ????????b.txt -- 写出数据 -- 字符转换流 -- OutputStreamWriter

*/

class CopyFileDemo {

????public?static?void main(String[] args) throws IOException {

????????// 封装数据源

????????InputStreamReader isr = new InputStreamReader(new FileInputStream(

????????????????"a.txt"));

????????// 封装目的地

????????OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream(

????????????????"b.txt"));

?

????????// 读写数据

????????// 方式1

????????// int?ch = 0;

????????// while ((ch = isr.read()) != -1) {

????????// osw.write(ch);

????????// }

?

????????// 方式2

????????char[] chs = new?char[1024];

????????int?len = 0;

????????while ((len = isr.read(chs)) != -1) {

????????????osw.write(chs, 0, len);

????????????// osw.flush();

????????}

?

????????// 释放资源

????????osw.close();

????????isr.close();

????}

}

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

?

/*

* 由于我们常见的操作都是使用本地默认编码，所以，不用指定编码。

* 而转换流的名称有点长，所以，Java就提供了其子类供我们使用。

* OutputStreamWriter = FileOutputStream + 编码表(GBK)

* FileWriter = FileOutputStream + 编码表(GBK)

*

* InputStreamReader = FileInputStream + 编码表(GBK)

* FileReader = FileInputStream + 编码表(GBK)

*

/*

* 需求：把当前项目目录下的a.txt内容复制到当前项目目录下的b.txt中

*

* 数据源：

* ????????a.txt -- 读取数据 -- 字符转换流 -- InputStreamReader -- FileReader

* 目的地：

* ????????b.txt -- 写出数据 -- 字符转换流 -- OutputStreamWriter -- FileWriter

*/

class CopyFileDemo2 {

????public?static?void main(String[] args) throws IOException {

????????// 封装数据源

????????FileReader fr = new FileReader("a.txt");

????????// 封装目的地

????????FileWriter fw = new FileWriter("b.txt");

?

????????// 一次一个字符

????????// int?ch = 0;

????????// while ((ch = fr.read()) != -1) {

????????// fw.write(ch);

????????// }

?

????????// 一次一个字符数组

????????char[] chs = new?char[1024];

????????int?len = 0;

????????while ((len = fr.read(chs)) != -1) {

????????????fw.write(chs, 0, len);

????????????fw.flush();

????????}

?

????????// 释放资源

????????fw.close();

????????fr.close();

????}

}

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

?

/*

* 字符缓冲流的特殊方法：

* BufferedWriter:

* ????????public void newLine():根据系统来决定换行符，并插入换行符

* BufferedReader:

* ????????public String readLine()：一次读取一行数据

* ????????包含该行内容的字符串，不包含任何行终止符，如果已到达流末尾，则返回 null

*/

class BufferedDemo {

????public?static?void main(String[] args) throws IOException {

????????// write();

????????read();

????}

?

????private?static?void read() throws IOException {

????????// 创建字符缓冲输入流对象

????????BufferedReader br = new BufferedReader(new FileReader("bw2.txt"));

?

????????// public String readLine()：一次读取一行数据

????????// String line = br.readLine();

????????// System.out.println(line);

????????// line = br.readLine();

????????// System.out.println(line);

?

????????// 最终版代码

????????String line = null;

????????while ((line = br.readLine()) != null) {

????????????System.out.println(line);

????????}

????????

????????//释放资源

????????br.close();

????}

?

????private?static?void?write() throws IOException {

????????// 创建字符缓冲输出流对象

????????BufferedWriter bw = new BufferedWriter(new FileWriter("bw2.txt"));

????????for (int?x = 0; x < 10; x++) {

????????????bw.write("hello" + x);

????????????// bw.write("\r\n");

????????????bw.newLine();

????????????bw.flush();

????????}

????????bw.close();

????}

?

}

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

?

/*

* BufferedReader

* 从字符输入流中读取文本，缓冲各个字符，从而实现字符、数组和行的高效读取。

* 可以指定缓冲区的大小，或者可使用默认的大小。大多数情况下，默认值就足够大了。

*

* BufferedReader(Reader in)

*/

class BufferedReaderDemo {

????public?static?void main(String[] args) throws IOException {

????????// 创建字符缓冲输入流对象

????????BufferedReader br = new BufferedReader(new FileReader("bw.txt"));

?

????????// 方式1

????????// int?ch = 0;

????????// while ((ch = br.read()) != -1) {

????????// System.out.print((char) ch);

????????// }

?

????????// 方式2

????????char[] chs = new?char[1024];

????????int?len = 0;

????????while ((len = br.read(chs)) != -1) {

????????????System.out.print(new String(chs, 0, len));

????????}

?

????????// 释放资源

????????br.close();

????}

}

import java.io.BufferedWriter;

import java.io.FileWriter;

import java.io.IOException;

?

/*

* 字符流为了高效读写，也提供了对应的字符缓冲流。

* BufferedWriter:字符缓冲输出流

* BufferedReader:字符缓冲输入流

*

* BufferedWriter:字符缓冲输出流

* 将文本写入字符输出流，缓冲各个字符，从而提供单个字符、数组和字符串的高效写入。

* 可以指定缓冲区的大小，或者接受默认的大小。在大多数情况下，默认值就足够大了。

*/

class BufferedWriterDemo {

????public?static?void main(String[] args) throws IOException {

????????// BufferedWriter(Writer out)

????????// BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(

????????// new FileOutputStream("bw.txt")));

?

????????BufferedWriter bw = new BufferedWriter(new FileWriter("bw.txt"));

?

????????bw.write("hello");

????????bw.write("world");

????????bw.write("java");

????????bw.flush();

?

????????bw.close();

????}

}

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

?

/*

* 需求：把当前项目目录下的a.txt内容复制到当前项目目录下的b.txt中

*

* 数据源：

* ????????a.txt -- 读取数据 -- 字符转换流 -- InputStreamReader -- FileReader -- BufferedReader

* 目的地：

* ????????b.txt -- 写出数据 -- 字符转换流 -- OutputStreamWriter -- FileWriter -- BufferedWriter

*/

class CopyFileDemo {

????public?static?void main(String[] args) throws IOException {

????????// 封装数据源

????????BufferedReader br = new BufferedReader(new FileReader("a.txt"));

????????// 封装目的地

????????BufferedWriter bw = new BufferedWriter(new FileWriter("b.txt"));

?

????????// 两种方式其中的一种一次读写一个字符数组

????????char[] chs = new?char[1024];

????????int?len = 0;

????????while ((len = br.read(chs)) != -1) {

????????????bw.write(chs, 0, len);

????????????bw.flush();

????????}

?

????????// 释放资源

????????bw.close();

????????br.close();

????}

}

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

?

/*

* 需求：把当前项目目录下的a.txt内容复制到当前项目目录下的b.txt中

* 要求：使用BufferReader的特有方法:readLine(),一次读取一行数据

* 数据源：

* ????????a.txt -- 读取数据 --

* 目的地：

* ????????b.txt -- 写出数据 --

*/

class CopyFileDemo2 {

????public?static?void main(String[] args) throws IOException {

????????// 封装数据源

????????BufferedReader br = new BufferedReader(new FileReader("a.txt"));

????????// 封装目的地

????????BufferedWriter bw = new BufferedWriter(new FileWriter("b.txt"));

?

????????// 读写数据

????????String line = null;

????????while ((line = br.readLine()) != null) {

????????????bw.write(line);

????????????bw.newLine();//写入一个换行符

????????????bw.flush();//刷新缓冲区

????????}

?

????????// 释放资源

????????bw.close();

????????br.close();

????}

}

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

?

/*

* 复制文本文件

*

* 分析：

* ????????复制数据，如果我们知道用记事本打开并能够读懂，就用字符流，否则用字节流。

* ????????通过该原理，我们知道我们应该采用字符流更方便一些。

* ????????而字符流有5种方式，所以做这个题目我们有5种方式。推荐掌握第5种。

* 数据源：

* ????????c:\\a.txt -- FileReader -- BufferdReader

* 目的地：

* ????????d:\\b.txt -- FileWriter -- BufferedWriter

*/

class CopyFileDemo {

????public?static?void main(String[] args) throws IOException {

????????String srcString = "c:\\a.txt";

????????String destString = "d:\\b.txt";

????????// method1(srcString, destString);

????????// method2(srcString, destString);

????????// method3(srcString, destString);

????????// method4(srcString, destString);

????????method5(srcString, destString);

????}

?

????// 方式5：字符缓冲流一次读写一个字符串

????private?static?void method5(String srcString, String destString)

????????????throws IOException {

????????//创建缓冲区对象

????????BufferedReader br = new BufferedReader(new FileReader(srcString));

????????BufferedWriter bw = new BufferedWriter(new FileWriter(destString));

?

????????String line = null;

????????while ((line = br.readLine()) != null) {

????????????//把字符串写入到文件中

????????????bw.write(line);

????????????//向文件中写入一个换行符

????????????bw.newLine();

????????????//刷新缓冲区

????????????bw.flush();

????????}

????????//关闭资源

????????bw.close();

????????br.close();

????}

?

????// 方式4：字符缓冲流一次读写一个字符数组

????private?static?void?method4(String srcString, String destString)

????????????throws IOException {

????????//创建缓冲区对象

????????BufferedReader br = new BufferedReader(new FileReader(srcString));

????????BufferedWriter bw = new BufferedWriter(new FileWriter(destString));

????????//创建字符数组

????????char[] chs = new?char[1024];

????????int?len = 0;

????????while ((len = br.read(chs)) != -1) {

????????????bw.write(chs, 0, len);

????????}

????????//关闭资源

????????bw.close();

????????br.close();

????}

?

????// 方式3：字符缓冲流一次读写一个字符

????private?static?void?method3(String srcString, String destString)

????????????throws IOException {

????????//创建缓冲区对象

????????BufferedReader br = new BufferedReader(new FileReader(srcString));

????????BufferedWriter bw = new BufferedWriter(new FileWriter(destString));

?

????????int?ch = 0;

????????while ((ch = br.read()) != -1) {

????????????bw.write(ch);

????????}

????????//关闭资源

????????bw.close();

????????br.close();

????}

?

????// 方式2：基本字符流一次读写一个字符数组

????private?static?void?method2(String srcString, String destString)

????????????throws IOException {

????????//创建基本字符流对象

????????FileReader fr = new FileReader(srcString);

????????FileWriter fw = new FileWriter(destString);

????????//创建一个字符数组

????????char[] chs = new?char[1024];

????????int?len = 0;

????????while ((len = fr.read(chs)) != -1) {

????????????fw.write(chs, 0, len);

????????}

????????//关闭资源

????????fw.close();

????????fr.close();

????}

?

????// 基本字符流一次读写一个字符

????private?static?void?method1(String srcString, String destString)

????????????throws IOException {

????????//创建基本字符流对象

????????FileReader fr = new FileReader(srcString);

????????FileWriter fw = new FileWriter(destString);

?

????????int?ch = 0;

????????while ((ch = fr.read()) != -1) {

????????????fw.write(ch);

????????}

????????//关闭资源

????????fw.close();

????????fr.close();

????}

}

import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

?

/*

* 复制图片

*

* 分析：

* ????????复制数据，如果我们知道用记事本打开并能够读懂，就用字符流，否则用字节流。

* ????????通过该原理，我们知道我们应该采用字节流。

* ????????而字节流有4种方式，所以做这个题目我们有4种方式。推荐掌握第4种。

*

* 数据源：

* ????????c:\\a.jpg -- FileInputStream -- BufferedInputStream

* 目的地：

* ????????d:\\b.jpg -- FileOutputStream -- BufferedOutputStream

*/

class CopyImageDemo {

????public?static?void main(String[] args) throws IOException {

????????// 使用字符串作为路径

????????// String srcString = "c:\\a.jpg";

????????// String destString = "d:\\b.jpg";

????????// 使用File对象做为参数

????????File srcFile = new File("c:\\a.jpg");

????????File destFile = new File("d:\\b.jpg");

?

????????// method1(srcFile, destFile);

????????// method2(srcFile, destFile);

????????// method3(srcFile, destFile);

????????method4(srcFile, destFile);

????}

?

????// 方式4：字节缓冲流一次读写一个字节数组

????private?static?void method4(File srcFile, File destFile) throws IOException {

????????//创建字节缓冲流对象

????????BufferedInputStream bis = new BufferedInputStream(new FileInputStream(

????????????????srcFile));

????????BufferedOutputStream bos = new BufferedOutputStream(

????????????????new FileOutputStream(destFile));

????????//创建byte数组

????????byte[] bys = new?byte[1024];

????????int?len = 0;

????????while ((len = bis.read(bys)) != -1) {

????????????bos.write(bys, 0, len);

????????}

????????//关闭资源

????????bos.close();

????????bis.close();

????}

?

????// 方式3：字节缓冲流一次读写一个字节

????private?static?void?method3(File srcFile, File destFile) throws IOException {

????????//创建字节缓冲流对象

????????BufferedInputStream bis = new BufferedInputStream(new FileInputStream(

????????????????srcFile));

????????BufferedOutputStream bos = new BufferedOutputStream(

????????????????new FileOutputStream(destFile));

?

????????int?by = 0;

????????while ((by = bis.read()) != -1) {

????????????bos.write(by);

????????}

????????//关闭资源

????????bos.close();

????????bis.close();

????}

?

????// 方式2：基本字节流一次读写一个字节数组

????private?static?void?method2(File srcFile, File destFile) throws IOException {

????????//创建基本字节流对象

????????FileInputStream fis = new FileInputStream(srcFile);

????????FileOutputStream fos = new FileOutputStream(destFile);

????????//创建字节数组

????????byte[] bys = new?byte[1024];

????????int?len = 0;

????????while ((len = fis.read(bys)) != -1) {

????????????fos.write(bys, 0, len);

????????}

????????//关闭资源

????????fos.close();

????????fis.close();

????}

?

????// 方式1：基本字节流一次读写一个字节

????private?static?void?method1(File srcFile, File destFile) throws IOException {

????????//创建基本字节流对象

????????FileInputStream fis = new FileInputStream(srcFile);

????????FileOutputStream fos = new FileOutputStream(destFile);

?

????????int?by = 0;

????????while ((by = fis.read()) != -1) {

????????????fos.write(by);

????????}

????????//关闭资源

????????fos.close();

????????fis.close();

????}

}

import java.io.BufferedWriter;

import java.io.FileWriter;

import java.io.IOException;

import java.util.ArrayList;

?

/*

* 需求：把ArrayList集合中的字符串数据存储到文本文件

*

* 分析：

* ????????通过题目的意思我们可以知道如下的一些内容，

* ????????????ArrayList集合里存储的是字符串。

* ????????????遍历ArrayList集合，把数据获取到。

* ????????????然后存储到文本文件中。

* ????????????文本文件说明使用字符流。

*

* 数据源：

* ????????ArrayList<String> -- 遍历得到每一个字符串数据

* 目的地：

* ????????a.txt -- FileWriter -- BufferedWriter

*/

class ArrayListToFileDemo {

????public?static?void main(String[] args) throws IOException {

????????// 封装数据与(创建集合对象)

????????ArrayList<String> array = new ArrayList<String>();

????????array.add("hello");

????????array.add("world");

????????array.add("java");

?

????????// 封装目的地

????????BufferedWriter bw = new BufferedWriter(new FileWriter("a.txt"));

?

????????// 遍历集合

????????for (String s : array) {

????????????// 写数据

????????????bw.write(s);

????????????//向文件中写入一个换行符

????????????bw.newLine();

????????????bw.flush();

????????}

?

????????// 释放资源

????????bw.close();

????}

}

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

import java.util.ArrayList;

?

/*

* 需求：从文本文件中读取数据(每一行为一个字符串数据)到集合中，并遍历集合

*

* 分析：

* ????????通过题目的意思我们可以知道如下的一些内容，

* ????????????数据源是一个文本文件。

* ????????????目的地是一个集合。

* ????????????而且元素是字符串。

*

* 数据源：

* ????????b.txt -- FileReader -- BufferedReader

* 目的地：

* ????????ArrayList<String>

*/

class FileToArrayListDemo {

????public?static?void main(String[] args) throws IOException {

????????// 封装数据源

????????BufferedReader br = new BufferedReader(new FileReader("b.txt"));

????????// 封装目的地(创建集合对象)

????????ArrayList<String> array = new ArrayList<String>();

?

????????// 读取数据存储到集合中

????????String line = null;

????????while ((line = br.readLine()) != null) {

????????????array.add(line);

????????}

?

????????// 释放资源

????????br.close();

?

????????// 遍历集合

????????for (String s : array) {

????????????System.out.println(s);

????????}

????}

}

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

import java.util.ArrayList;

import java.util.Random;

?

/*

* 需求：我有一个文本文件中存储了几个名称，请大家写一个程序实现随机获取一个人的名字。

*

* 分析：

* ????????A:把文本文件中的数据存储到集合中

* ????????B:随机产生一个索引

* ????????C:根据该索引获取一个值

*/

class GetName {

????public?static?void main(String[] args) throws IOException {

????????// 把文本文件中的数据存储到集合中

????????BufferedReader br = new BufferedReader(new FileReader("b.txt"));

????????ArrayList<String> array = new ArrayList<String>();

????????String line = null;

????????while ((line = br.readLine()) != null) {

????????????array.add(line);

????????}

????????br.close();

?

????????// 随机产生一个索引

????????Random r = new Random();

????????int?index = r.nextInt(array.size());

?

????????// 根据该索引获取一个值

????????String name = array.get(index);

????????System.out.println("该幸运者是：" + name);

????}

}

import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

?

/*

* 需求：复制单极文件夹

*

* 数据源：e:\\demo

* 目的地：e:\\test

*

* 分析：

* ????????A:封装目录

* ????????B:获取该目录下的所有文件的File数组

* ????????C:遍历该File数组，得到每一个File对象

* ????????D:把该File进行复制

*/

class CopyFolderDemo {

????public?static?void main(String[] args) throws IOException {

????????// 封装目录

????????File srcFolder = new File("e:\\demo");

????????// 封装目的地

????????File destFolder = new File("e:\\test");

????????// 如果目的地文件夹不存在，就创建

????????if (!destFolder.exists()) {

????????????destFolder.mkdir();

????????}

?

????????// 获取该目录下的所有文本的File数组

????????File[] fileArray = srcFolder.listFiles();

?

????????// 遍历该File数组，得到每一个File对象

????????for (File file : fileArray) {

????????????// System.out.println(file);

????????????// 数据源：e:\\demo\\e.mp3

????????????// 目的地：e:\\test\\e.mp3

????????????String name = file.getName(); // e.mp3

????????????File newFile = new File(destFolder, name); // e:\\test\\e.mp3

?

????????????copyFile(file, newFile);

????????}

????}

????//复制文件：将一个地方的文件复制到另外一个地方

????private?static?void copyFile(File file, File newFile) throws IOException {

????????BufferedInputStream bis = new BufferedInputStream(new FileInputStream(

????????????????file));

????????BufferedOutputStream bos = new BufferedOutputStream(

????????????????new FileOutputStream(newFile));

?

????????byte[] bys = new?byte[1024];

????????int?len = 0;

????????while ((len = bis.read(bys)) != -1) {

????????????bos.write(bys, 0, len);

????????}

?

????????bos.close();

????????bis.close();

????}

}

import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.FilenameFilter;

import java.io.IOException;

?

/*

* 需求：复制指定目录下的指定文件，并修改后缀名。

* 指定的文件是：.java文件。

* 指定的后缀名是：.jad

* 指定的目录是：jad

*

* 数据源：e:\\java\\A.java

* 目的地：e:\\jad\\A.jad

*

* 分析：

* ????????A:封装目录

* ????????B:获取该目录下的java文件的File数组

* ????????C:遍历该File数组，得到每一个File对象

* ????????D:把该File进行复制

* ????????E:在目的地目录下改名

*/

class CopyFolderDemo {

????public?static?void main(String[] args) throws IOException {

????????// 封装目录

????????File srcFolder = new File("e:\\java");

????????// 封装目的地

????????File destFolder = new File("e:\\jad");

????????// 如果目的地目录不存在，就创建

????????if (!destFolder.exists()) {

????????????destFolder.mkdir();

????????}

?

????????// 获取该目录下的java文件的File数组

????????File[] fileArray = srcFolder.listFiles(new FilenameFilter() {

????????????@Override

????????????public?boolean accept(File dir, String name) {

????????????????return?new File(dir, name).isFile() && name.endsWith(".java");

????????????}

????????});

?

????????// 遍历该File数组，得到每一个File对象

????????for (File file : fileArray) {

????????????// System.out.println(file);

????????????// 数据源：e:\java\DataTypeDemo.java

????????????// 目的地：e:\\jad\DataTypeDemo.java

????????????String name = file.getName();

????????????File newFile = new File(destFolder, name);

????????????copyFile(file, newFile);

????????}

?

????????// 在目的地目录下改名

????????File[] destFileArray = destFolder.listFiles();

????????for (File destFile : destFileArray) {

????????????// System.out.println(destFile);

????????????// e:\jad\DataTypeDemo.java

????????????// e:\\jad\\DataTypeDemo.jad

????????????String name =destFile.getName(); //DataTypeDemo.java

????????????String newName = name.replace(".java", ".jad");//DataTypeDemo.jad

????????????

????????????File newFile = new File(destFolder,newName);

????????????destFile.renameTo(newFile);

????????}

????}

?

????private?static?void copyFile(File file, File newFile) throws IOException {

????????BufferedInputStream bis = new BufferedInputStream(new FileInputStream(

????????????????file));

????????BufferedOutputStream bos = new BufferedOutputStream(

????????????????new FileOutputStream(newFile));

?

????????byte[] bys = new?byte[1024];

????????int?len = 0;

????????while ((len = bis.read(bys)) != -1) {

????????????bos.write(bys, 0, len);

????????}

?

????????bos.close();

????????bis.close();

????}

}

import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

?

/*

* 需求：复制多极文件夹

*

* 数据源：E:\JavaSE\day21\code\demos

* 目的地：E:\\

*

* 分析：

* ????????A:封装数据源File

* ????????B:封装目的地File

* ????????C:判断该File是文件夹还是文件

* ????????????a:是文件夹

* ????????????????就在目的地目录下创建该文件夹

* ????????????????获取该File对象下的所有文件或者文件夹File对象

* ????????????????遍历得到每一个File对象

* ????????????????回到C

* ????????????b:是文件

* ????????????????就复制(字节流)

*/

class CopyFoldersDemo {

????public?static?void main(String[] args) throws IOException {

????????// 封装数据源File

????????File srcFile = new File("E:\\JavaSE\\day21\\code\\demos");

????????// 封装目的地File

????????File destFile = new File("E:\\");

?

????????// 复制文件夹的功能

????????copyFolder(srcFile, destFile);

????}

?

????private?static?void copyFolder(File srcFile, File destFile)

????????????throws IOException {

????????// 判断该File是文件夹还是文件

????????if (srcFile.isDirectory()) {

????????????// 文件夹

????????????File newFolder = new File(destFile, srcFile.getName());

????????????newFolder.mkdir();

?

????????????// 获取该File对象下的所有文件或者文件夹File对象

????????????File[] fileArray = srcFile.listFiles();

????????????for (File file : fileArray) {

????????????????copyFolder(file, newFolder);

????????????}

????????} else {

????????????// 文件

????????????File newFile = new File(destFile, srcFile.getName());

????????????copyFile(srcFile, newFile);

????????}

????}

?

????private?static?void copyFile(File srcFile, File newFile) throws IOException {

????????BufferedInputStream bis = new BufferedInputStream(new FileInputStream(

????????????????srcFile));

????????BufferedOutputStream bos = new BufferedOutputStream(

????????????????new FileOutputStream(newFile));

?

????????byte[] bys = new?byte[1024];

????????int?len = 0;

????????while ((len = bis.read(bys)) != -1) {

????????????bos.write(bys, 0, len);

????????}

?

????????bos.close();

????????bis.close();

????}

}

public?class Student {

????// 姓名

????private String name;

????// 语文成绩

????private?int?chinese;

????// 数学成绩

????private?int?math;

????// 英语成绩

????private?int?english;

?

????public Student() {

????????super();

????}

?

????public Student(String name, int?chinese, int?math, int?english) {

????????super();

????????this.name = name;

????????this.chinese = chinese;

????????this.math = math;

????????this.english = english;

????}

?

????public String getName() {

????????return?name;

????}

?

????public?void setName(String name) {

????????this.name = name;

????}

?

????public?int getChinese() {

????????return?chinese;

????}

?

????public?void setChinese(int?chinese) {

????????this.chinese = chinese;

????}

?

????public?int getMath() {

????????return?math;

????}

?

????public?void setMath(int?math) {

????????this.math = math;

????}

?

????public?int getEnglish() {

????????return?english;

????}

?

????public?void setEnglish(int?english) {

????????this.english = english;

????}

????//获取成绩的总分

????public?int getSum() {

????????return?this.chinese + this.math + this.english;

????}

}

import java.io.BufferedWriter;

import java.io.FileWriter;

import java.io.IOException;

import java.util.Comparator;

import java.util.Scanner;

import java.util.TreeSet;

?

/*

* 键盘录入5个学生信息(姓名,语文成绩,数学成绩,英语成绩),按照总分从高到低存入文本文件

*

* 分析：

* ????????A:创建学生类

* ????????B:创建集合对象

* ????????????TreeSet<Student>

* ????????C:键盘录入学生信息存储到集合

* ????????D:遍历集合，把数据写到文本文件

*/

class StudentDemo {

????public?static?void main(String[] args) throws IOException {

????????// 创建集合对象

????????TreeSet<Student> ts = new TreeSet<Student>(new Comparator<Student>() {

????????????@Override

????????????public?int compare(Student s1, Student s2) {

????????????????int?num = s2.getSum() - s1.getSum();

????????????????int?num2 = num == 0 ? s1.getChinese() - s2.getChinese() : num;

????????????????int?num3 = num2 == 0 ? s1.getMath() - s2.getMath() : num2;

????????????????int?num4 = num3 == 0 ? s1.getEnglish() - s2.getEnglish() : num3;

????????????????int?num5 = num4 == 0 ? s1.getName().compareTo(s2.getName())

????????????????????????: num4;

????????????????return?num5;

????????????}

????????});

?

????????// 键盘录入学生信息存储到集合

????????for (int?x = 1; x <= 5; x++) {

????????????Scanner sc = new Scanner(System.in);

????????????System.out.println("请录入第" + x + "个的学习信息");

????????????System.out.println("姓名：");

????????????String name = sc.nextLine();

????????????System.out.println("语文成绩：");

????????????int?chinese = sc.nextInt();

????????????System.out.println("数学成绩：");

????????????int?math = sc.nextInt();

????????????System.out.println("英语成绩：");

????????????int?english = sc.nextInt();

?

????????????// 创建学生对象

????????????Student s = new Student();

????????????s.setName(name);

????????????s.setChinese(chinese);

????????????s.setMath(math);

????????????s.setEnglish(english);

?

????????????// 把学生信息添加到集合

????????????ts.add(s);

????????}

?

????????// 遍历集合，把数据写到文本文件

????????BufferedWriter bw = new BufferedWriter(new FileWriter("students.txt"));

????????bw.write("学生信息如下：");

????????bw.newLine();

????????bw.flush();

????????bw.write("姓名,语文成绩,数学成绩,英语成绩");

????????bw.newLine();

????????bw.flush();

????????for (Student s : ts) {

????????????StringBuilder sb = new StringBuilder();

????????????sb.append(s.getName()).append(",").append(s.getChinese())

????????????????????.append(",").append(s.getMath()).append(",")

????????????????????.append(s.getEnglish());

????????????bw.write(sb.toString());

????????????bw.newLine();

????????????bw.flush();

????????}

????????// 释放资源

????????bw.close();

????????System.out.println("学习信息存储完毕");

????}

}

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

import java.util.Arrays;

?

/*

* 已知s.txt文件中有这样的一个字符串："hcexfgijkamdnoqrzstuvwybpl"

* 请编写程序读取数据内容，把数据排序后写入ss.txt中。

*

* 分析：

* ????????A:把s.txt这个文件给做出来

* ????????B:读取该文件的内容，存储到一个字符串中

* ????????C:把字符串转换为字符数组

* ????????D:对字符数组进行排序

* ????????E:把排序后的字符数组转换为字符串

* ????????F:把字符串再次写入ss.txt中

*/

class StringDemo {

????public?static?void main(String[] args) throws IOException {

????????// 读取该文件的内容，存储到一个字符串中

????????BufferedReader br = new BufferedReader(new FileReader("s.txt"));

????????String line = br.readLine();

????????br.close();

?

????????// 把字符串转换为字符数组

????????char[] chs = line.toCharArray();

?

????????// 对字符数组进行排序

????????Arrays.sort(chs);

?

????????// 把排序后的字符数组转换为字符串

????????String s = new String(chs);

?

????????// 把字符串再次写入ss.txt中

????????BufferedWriter bw = new BufferedWriter(new FileWriter("ss.txt"));

????????bw.write(s);

????????bw.newLine();

????????bw.flush();

?

????????bw.close();

????}

}

import java.io.IOException;

import java.io.Reader;

?

/*

* 用Reader模拟BufferedReader的readLine()功能

*

* readLine():一次读取一行，根据换行符判断是否结束，只返回内容，不返回换行符

*/