java字节流、字符流与转换流过程

public abstract class OutputStream extends Object implements Closeable,Flushable

public abstract class InputStream extends Object implements Closeable

package com.booy;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class ByteStreamDemo {
	//读文件
	public static void In() {
		//确定要写入的目标文件
		File file = new File("D:\\test\\test.txt");
		//构建一个文件输入流对象
		try {
			InputStream in = new FileInputStream(file);
			
			//把文件内容读出到程序中
			byte[] bytes = new byte[1024];
			StringBuilder buf = new StringBuilder();
			int len = -1;//表示每次读取的字节长度
			//把数据读入到数组中，并返回读取的字节数，当不等于-1时，表示读取到数据，等于-1表示文件已经读完
			while((len=in.read(bytes))!=-1) {
				//根据读取到的字节数组，再转换为字符串内容，添加到StringBuilder中
				buf.append(new String(bytes));
			}	
			//测试打印
			System.out.println("文件读入成功："+buf);
			//关闭流
			in.close();
			
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	//写文件
	public static void Out() {
		//确定要输出的目标文件
		File file = new File("D:\\test\\test.txt");
		
		//构建一个文件输出流对象
		try {
			OutputStream out = new FileOutputStream(file,true);//true不写为替换
			//输出的内容
			String info = "小桥流水人家\r\t";
			//把内容写入到文件中
			out.write(info.getBytes());
			//关闭流
			out.close();
			System.out.println("文件写入成功！");
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	public static void main(String[] args) {
		Out();
		In();		
	}
}
/**
运行结果：
文件写入成功！
文件读入成功： 小桥流水人家
	小桥流水人家
*/

package com.booy;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Reader;
import java.io.Writer;

public class CharStreamtDemo {

	public static void main(String[] args) {
		Out();
		In();
	}
	private static void In() {
		File file = new File("D:\\test\\test.txt");
		try {
			Reader in = new FileReader(file);
			
			char[] cs = new char[1];
			StringBuilder sbl = new StringBuilder();
			int len = -1;
			while((len=in.read(cs))!=-1) {
				sbl.append(cs, 0, cs.length);
			}
			System.out.println(sbl);
			in.close();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	private static void Out() {
		File file = new File("D:\\test\\test.txt");
		try {
			Writer out = new FileWriter(file,true);
			out.write(",古道西风瘦马");
			out.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}
/**
运行结果：
 小桥流水人家,古道西风瘦马
*/

package com.booy;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class CopyFileDemo {
	public static void main(String[] args) {
		copy("D:\\test\\1.jpg","D:\\test\\my\\1.jpg");
	}
	private static void copy(String src,String target) {
		File srcFile = new File(src);
		File targetFile = new File(target);
		InputStream in =null;
		OutputStream out =null;
		try {
			in =new FileInputStream(srcFile);
			out =new FileOutputStream(targetFile);
			
			byte[] bytes = new byte[1024];
			int len = -1;
			while((len=in.read(bytes))!=-1) {
				out.write(bytes, 0, len);
			}			
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		finally {
			try {
				if(in!=null)in.close();
				if(out!=null)out.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
}

package com.booy;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.Writer;
import java.nio.charset.Charset;

public class ChangerStringDemo {

	public static void main(String[] args) throws FileNotFoundException {
		//InputStream in = new FileInputStream("D:\\test\\test.txt");
		//read(in);
		OutputStream out = new FileOutputStream("D:\\test\\test.txt");
		writer(out);
	}
	private static void read(InputStream in) {
		Reader reader = new InputStreamReader(in,Charset.defaultCharset());
		
		char[] cs = new char[1024];
		int len = -1;
		try {
			while((len=reader.read(cs))!=-1) {
				System.out.println(new String(cs,0,len));
			}
			cs.clone();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	private static void writer(OutputStream out) {
		Writer writ = new OutputStreamWriter(out,Charset.defaultCharset());
		try {
			writ.write("夕阳西下，断肠人在天涯");
			writ.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}