Java基础二十
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1 转换流
1.1 转换流出现的原因
- 由于字节流操作中文的时候不是很方便,所以,Java就提供了转换流。
- 字符流=字节流+编码表。
1.2 String类的编码和解码功能
- 方法:通过指定的编码,将二进制的数据转换为字符串,即解码
String(byte[] bytes, Charset charset)
- 方法:通过制定的编码,将字符串转换为二进制的数据,即编码
public byte[] getBytes(Charset charset)
- 示例:
package com.xuweiwei; import java.io.UnsupportedEncodingException; public class StringDemo { public static void main(String[] args) throws UnsupportedEncodingException { String str = "abcdef"; //编码 byte[] bytes = str.getBytes("UTF-8"); for (byte aByte : bytes) { System.out.println("aByte = " + aByte +"、" ); } //解码 System.out.println("解码:"+new String(bytes,"UTF-8")); } }
2 OutputStreamWriter
- 作用:将字节输出流转换为字符输出流。
- 构造方法:根据指定的编码将字节流转换为字符流
public OutputStreamWriter(OutputStream out, String charsetName) throws UnsupportedEncodingException
- 示例:
package com.xuweiwei; import java.io.*; public class OutputStreamWriterDemo { public static void main(String[] args) throws IOException { Writer ow = new OutputStreamWriter(new FileOutputStream("ow.txt"),"utf-8"); ow.write("你好,许威威"); ow.close(); } }
3 InputStreamReader
- 将字节输入流转换为字符输入流
- 构造方法:
public InputStreamReader(InputStream in, String charsetName) throws UnsupportedEncodingException
- 示例:
package com.xuweiwei; import java.io.*; public class InputStreamReaderDemo { public static void main(String[] args) throws IOException { Reader reader = new InputStreamReader(new FileInputStream("ow.txt"),"utf-8"); char[] buffer = new char[1024]; int len = 0; while(-1 != (len = reader.read(buffer))){ System.out.println(new String(buffer,0,len)); } reader.close(); } }
4 转换流的简化写法
- 抓换流的名字比较长,而我们常见的操作都是按照本地默认编码实现的,所以, 为了简化我们的书写,转换流就提供了对应的子类。
- 例如:FileWriter和FileReader。
- 示例:
package com.xuweiwei; import java.io.FileWriter; import java.io.IOException; public class FileWriterDemo { public static void main(String[] args) throws IOException { FileWriter fw = new FileWriter("fw.txt"); fw.write("你好啊"); fw.close(); } }
5 字符缓冲流
- BufferedWriter
- 特殊功能:写一个行分隔符
public void newLine() throws IOException
- BufferedReader
- 特殊功能:读一个行分隔符
public String readLine()
- 示例:
package com.xuweiwei; import java.io.*; public class BufferedWriterDemo { public static void main(String[] args) throws IOException { BufferedWriter bw = new BufferedWriter(new FileWriter("bw.txt")); bw.write("你好啊"); bw.flush(); bw.close(); } }
- 示例:
package com.xuweiwei; import java.io.FileWriter; import java.io.IOException; public class FileWriterDemo { public static void main(String[] args) throws IOException { FileWriter fw = new FileWriter("fw.txt"); fw.write("你好啊"); fw.close(); } }
- 示例:
package com.xuweiwei; import java.io.*; public class CopyDemo { public static void main(String[] args) throws IOException { BufferedReader br = new BufferedReader(new FileReader("br.txt")); BufferedWriter bw = new BufferedWriter(new FileWriter("bw.txt")); String line = null; while(null != (line = br.readLine())){ bw.write(line); bw.newLine(); bw.flush(); } bw.close(); br.close(); } }
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