IO流

先插入别人那里的一张图片

重要的就是read和write方法
以文件的复制为例
字节流

package cn.itcast.Copy;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import javax.management.RuntimeErrorException;

/*
 * 将d:\\a.txt
 * 复制到d:\\b.txt
 */
public class Copy {
	public static void main(String[] args)  {
		// 先创建两个流的对象
		FileInputStream fis = null;
		FileOutputStream fos = null;
		//捕获异常
		try{
		fis = new FileInputStream("d:\\a.txt");
		fos = new FileOutputStream("d:\\b.txt");
		//字节输入流，读一个字节，输出流写一个字节
		int len = 0;
		while((len = fis.read()) != -1){
			fos.write(len);
		}
		}catch (IOException e) {
			System.out.println(e);
			throw new RuntimeException("运行失败");
		}finally{
			try {
				if(fis != null)
				fis.close();
			} catch (Exception e2) {
				System.out.println(e2);
				throw new RuntimeException("关闭失败");
			}finally{
				try {
					if(fos != null )
					fos.close();
				} catch (Exception e3) {
					System.out.println(e3);
					throw new RuntimeException("关闭失败");
				}
			}
		}
	}
}

字符流

package cn.itcast.demo03;

import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

import javax.management.RuntimeErrorException;

/*
 *  将d:\\a.txt
 * 复制到d:\\b.txt
 */
public class Copy {
	public static void main(String[] args) {
		// 老样子，首先建立两个流的变量
		FileWriter fw = null;
		FileReader fr = null;
		// 捕获异常
		try {
			// 绑定数据源
			fr = new FileReader("d:\\a.txt");
			fw = new FileWriter("d:\\b.txt");
			int len = 0;
			char[] ch = new char[1024];
			while ((len = fr.read(ch)) != -1) {
				fw.write(ch, 0, len);
				fw.flush();
			}

		} catch (IOException e) {
			System.out.println(e);
			throw new RuntimeException("运行错误");
		} finally {
			try {
				if (fr != null)
					fr.close();
			} catch (Exception e2) {
				System.out.println(e2);
				throw new RuntimeException("关闭读入文件失败");
			} finally {
				try {
					if (fw != null)
						fw.close();
				} catch (Exception e2) {
					System.out.println(e2);
					throw new RuntimeException("关闭写入文件失败");
				}
			}
		}
	}
}

注意：字符流的write()方法后必须刷新，即必须跟着写flush()方法

缓冲流的构造方法中可以传递任意的字节输入输出流
BufferedWriter类特有的方法：
void newLine()
写入一个行分隔符。

Bufferedreader类特有的方法：
String readLine()
读取一个文本行

package cn.itcast.demo02;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

//利用字节输入输出缓冲流实现文件的复制
public class Copy {
	public static void main(String[] args) throws IOException {
		copyMethod(new File("d:\\buffered.txt"), new File("d:\\buffCopy.txt"));
	}

	private static void copyMethod(File src, File desc) throws IOException {
			BufferedInputStream bis = new BufferedInputStream(new FileInputStream(src));
			BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(desc));
			int len = 0;
			byte[] b = new byte[1024];
			while ((len = bis.read(b)) != -1) {
				bos.write(b,0,len);
			}
			bis.close();
			bos.close();
			
}
}