07 JAVA IO流 练习

1. OutputStream

import java.io.*;

public class TestOutputStream {
	public static void main(String[] args) {
		OutputStreamWriter osw;
		try {
			osw = new OutputStreamWriter(new FileOutputStream("/Users/apple/Desktop/io/char.txt"));
			osw.write("abcdefghijklmn我是几个汉字");
			System.out.println(osw.getEncoding()); //获取当前系统的默认编码
			osw.close();
			
			osw = new OutputStreamWriter(new FileOutputStream("/Users/apple/Desktop/io/char.txt", true), "ISO8859-1"); //true表示append，而不是删除重建
			osw.write("opqrstuvwxyz我是几个汉字");
			System.out.println(osw.getEncoding());
			osw.close();
			
		} catch (FileNotFoundException e) {
			System.out.println("找不到相关的文件！");
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

2. 复制文件

/**
 * 使用FileReader复制文件，但是我们却不可以使用FileReader复制图片，因为字符流就是字节流+编码表，
 * 使用字符流去复制图片，字符流会默认将图片的字节码格式进行编码，导致与原图片不一致
 */
import java.io.*;

public class CopyFile {
	public static void main(String[] args) {
		FileReader fr = null;
		FileWriter fw = null;
		String dir = "/Users/apple/Desktop/io/";
		int c = -1;
		//char[] cbuf = new char[60];
		
		try {
			fr = new FileReader(dir+"CopyFile.java");
			//如果文件不存在，会创建文件，但是不能创建子目录
			fw = new FileWriter(dir+"copiedFile.java");
			/*一次性装入60个字符到cbuf里面，如果不够会填充再返回-1
			 * while(fr.read(cbuf) != -1)
				System.out.println(cbuf);
			 */
			while((c = fr.read()) != -1) {
				fw.write(c);
			}
			fw.close(); 
			fr.close();
		} catch(FileNotFoundException fnfe) {
			System.out.println("找不到指定文件！");
			fnfe.printStackTrace();
			System.exit(-1);
		} catch(IOException ioe) {
			System.out.println("文件复制错误！");
			ioe.printStackTrace();
			System.exit(-1);
		}
		
		System.out.println("复制成功~");
	}
}

3. Buffer

import java.io.*;

public class TestBufferStream {
	public static void main(String[] args) {
		FileInputStream fis =null; 
		BufferedInputStream bis = null;
		BufferedReader br = null;
		BufferedWriter bw = null;
		try{
			fis = new FileInputStream("/Users/apple/Desktop/io/testBuffer.txt");
			bis = new BufferedInputStream(fis,15); //buffer的大小为10字节
			int c = 0;
			System.out.println((char)bis.read());
			System.out.println(bis.read());
			bis.mark(1);//标记当前位置，readlimit只是说用户读取多少个字节后，mark可能会失效（“可能”，而不是一定，因为这取决于buffer的大小）
			for(int i = 0; i<=10 && (c = bis.read())!=-1; i++) {
				System.out.print((char)c+" ");
			}
			System.out.println();
			bis.reset();//回到刚才标记的位置
			for(int i = 0; i<=10 && (c = bis.read())!=-1; i++) {
				System.out.print((char)c+" ");
			}
			System.out.println(); 
			bis.close();
			
			bw = new BufferedWriter(new FileWriter("/Users/apple/Desktop/io/testBuffer1.txt"));
			br = new BufferedReader(new FileReader("/Users/apple/Desktop/io/testBuffer1.txt"));
			String s = null;
			for(int i = 0; i < 50; i++) {
				s = String.valueOf(Math.random());
				bw.write(s);
				bw.newLine();//添加分隔符
			}
			bw.flush();
			while((s = br.readLine()) != null) {
				System.out.println(s);
			}
			bw.close();
			br.close();
		} catch(FileNotFoundException fe) {
			fe.getMessage();
		} catch(IOException e) {
			e.getMessage();
		}
	}
}

4. DataStream

import java.io.*;

public class TestDataStream {
	public static void main(String[] args) {
		//在内存中创建了一个byte类型数组空间，并且创建了一个输出流管道指向它
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		DataOutputStream dos = new DataOutputStream(baos);//套接
		try {
			dos.writeInt(100);
			dos.writeBoolean(true); //布尔型占一个字节
			ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
			System.out.println(bais.available());//有几个有效字节
			DataInputStream dis =  new DataInputStream(bais);
			//先进先出
			System.out.println(dis.readInt());
			System.out.println(dis.readBoolean());
			dos.close();
			dis.close();
		} catch(IOException e) {
			e.printStackTrace();
		}
	}
}

5. Object

import java.io.*;

class T implements Serializable {
	int x = 1;
	int y = 2;
	double z = 3.0;
	transient int k = 8;
}

public class TestObject {
	public static void main(String args[]) {
		T t = new T();
		t.k = 2;
		System.out.println(t.k);
		try {
			FileOutputStream fos = new FileOutputStream("/Users/apple/Desktop/io/t.bak");
			ObjectOutputStream oos = new ObjectOutputStream(fos);
			oos.writeObject(t);
			oos.flush();
			oos.close();
			
			FileInputStream fis = new FileInputStream("/Users/apple/Desktop/io/t.bak");
			ObjectInputStream ois = new ObjectInputStream(fis);
			T tr =  (T)ois.readObject();
			System.out.println("t.x:"+tr.x+" t.y:"+tr.y+" t.z:"+tr.z+" t.k:"+tr.k);
		} catch (FileNotFoundException e) {
			System.out.println("没有相关文件！");
		} catch(IOException e1) {
			System.out.println("对象写入失败！");
		} catch(ClassNotFoundException e2) {
			System.out.println("找不到对象类型！");
		}
	}
}

6. print

import java.io.*;

public class TestPrint {
	static void print(PrintStream ps) {
		ps.println("print~");
	}
	
	public static void main(String[] args) {
		PrintStream ps = null;
		try {
			FileOutputStream fos = new FileOutputStream("/Users/apple/Desktop/io/print1.dat");
			ps = new PrintStream(fos);
		} catch(FileNotFoundException e) {
			System.out.println("找不到相关文件！");
		}
		if(ps != null) {
			System.setOut(ps);//我们重置了输出位置
		}
		int ln = 0;
		for(char c = 0; c <= 100; c++) {
			System.out.print(c + " ");
			if(ln++ >= 25) {
				System.out.println();
				ln = 0;
			}
		}
		System.out.println();
		print(ps);
	}
}

7. System.in

import java.io.*;
import java.util.Date;

public class TestSystemIn {
	public static void main(String[] args) {
		String s = null;
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		try {
			FileWriter fw = new FileWriter("/Users/apple/Desktop/io/logFile.log",true);
			PrintWriter pw = new PrintWriter(fw);
			while((s = br.readLine()) != null) {
				if(s.equalsIgnoreCase("exit"))
					break;
				System.out.println(s.toUpperCase());
				pw.println("-----------------");
				pw.println(s.toUpperCase());
				pw.flush();
			}
			pw.println("======="+new Date()+"=======");
			pw.flush();
			br.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}