黑马程序员--第十九天：io流第二天

---------------------- ASP.Net+Android+IO开发S、.Net培训、期待与您交流！ ----------------------

 

import java.io.*;class BufferedWriterDemo {public static void main(String[] args) throws IOException{FileWriter fw = new FileWriter("but.txt");BufferedWriter bw = new BufferedWriter(fw);bw.write("abc");bw.flush();bw.close();System.out.println("Hello World!");}}/*sum:new BufferedWriter(fw);bw.write("abc");bw.flush();bw.close();*///19-2import java.io.*;class BufferedReaderDemo {public static void main(String[] args) throws IOException{FileReader fr = new FileReader("buf.txt");//返回：//  包含该行内容的字符串，不包含任何 行终止符(\r \n)，如果已到达流末尾，则返回 null BufferedReader br = new BufferedReader(fr);String line = null;while((line = br.readLine())!=null)//因为 String型 是个对象，当没有String对象时 返回null    //而 int 型的是数字，所以当标记没有长度是，用-1.System.out.println(line);br.close();}}/*sum:new BufferedReader(fr);br.readLine();*///19-3import java.io.*;class BufferedCopy {public static void main(String[] args) {BufferedReader br = null;BufferedWriter bw = null;try{ br = new BufferedReader(new FileReader("buf.txt")); bw = new BufferedWriter(new FileWriter("buf-copy.txt")); String line = null; while ((line = br.readLine())!=null) { bw.write(line); bw.newLine(); bw.flush(); }}catch (IOException e){throw new RuntimeException("读写失败");}finally{try{if (br != null)br.close();}catch (IOException e){throw new RuntimeException("读取失败");}try{if (bw != null)bw.close();}catch (IOException e){throw new RuntimeException("写入失败");}}System.out.println("Hello World!");}}/*sum:bw.newLine();*//*19-6装饰设计模式：当想要对已有的对象进行功能增强时，可以定义类，将已有对象传入，基于已有的功能，并提供加强功能。那么自定义的该类称为 装饰类。装饰类通常会通过构造函数接收被装饰类的对象，并基于被装饰的对象的功能，提供更强的功能。*//*19-7装饰者设计模式与继承的比较MyReader//专门用于读取数据-----继承的结构|--MyTextReader|--MyBufferTextReader|--MyMediaReader|--MyBufferMediaReader|--MyDataReader|--MyBufferDataReaderclass MyBufferReader{MyBufferReader(MyTextReader text){}MyBufferReader(MyMediaReader text){}MyBufferReader(MyDataReader text){}}该类的扩展性很差，找到其参数的共同类型，通过多态形式通过扩展性class MyBufferReader extends MyReader//继承公共父类，即MyReader，而不像继承结构中-继承MyReader的子类{MyBufferReader(MyReader r){}}MyReader//专门用于读取数据的类-----装饰模式的结构|--MyTextReader|--MyMediaReader|--MyDataReader|--MyBufferReader     //组合结构*///19-5import java.io.*;class MyBufferedReader extends Reader{private Reader fr = null;MyBufferedReader(Reader fr){this.fr = fr;}public String myReadLine() throws IOException{StringBuilder sb = new StringBuilder();   //StringBuilder();int ch = 0;while ((ch = fr.read())!= -1){if (ch=='\r')continue; // the keyword continue.if(ch == '\n')return sb.toString();sb.append((char)ch);}if (sb.length() != 0)return sb.toString(); //important to return the last line.return null;}public int read (char[] buf, int off, int len) throws IOException{return read (buf, off, len);//调用对象方法}public void close() throws IOException{fr.close();//调用对象方法}public void myClose() throws IOException{fr.close();}}class MyBufferedReaderDemo{public static void main(String[] args) throws IOException{FileReader fr = new FileReader("buf.txt");MyBufferedReader mr = new MyBufferedReader(fr);String line = null;while ((line = mr.myReadLine()) != null){System.out.println(line);}System.out.println("Hello World!");}}/*sum:continue;new StringBuilder();sb.append((char)ch);*//*sum:装饰者设计模式与继承的比较;多态调用对象方法;继承父类要复写抽象方法;*///19-9import java.io.*;class LineNumberReaderDemo {public static void main(String[] args) throws IOException{FileReader fr = new FileReader("buf.txt");LineNumberReader lnr = new LineNumberReader(fr);String line = null;lnr.setLineNumber(10000000);while ((line = lnr.readLine()) != null){System.out.println(lnr.getLineNumber()+":"+line);}lnr.close();}}/*sum:new LineNumberReader(fr);lnr.setLineNumber(10000000);lnr.getLineNumber();*///19-13import java.io.*;class CopyMp3 {public static void main (String[] args) throws IOException{long start = System.currentTimeMillis ();//学过的方法需要巩固，忘了就用不出来了copy_1();long end = System.currentTimeMillis();System.out.println(end-start);}public static void copy_1() throws IOException{//注意static的用法MyBufferedInputStream bis = new MyBufferedInputStream(new FileInputStream("F:\\s.mp3"));BufferedOutputStream bos = new BufferedOutputStream (new FileOutputStream("F:\\s-copy.mp3"));int b = 0;while ((b = bis.myRead())!=-1){bos.write(b);}bis.myClose();bos.close();}}/*sum://学过的方法需要巩固，忘了就用不出来了//注意static的用法*///19-14import java.io.*;class  MyBufferedInputStream{private InputStream is;private byte[] buf = new byte[1024];//Byte与byte是不同的2个属性int count = 0, pos = 0;MyBufferedInputStream(InputStream is){this.is = is;}public int myRead () throws IOException{//函数有返回值if (count == 0){count = is.read(buf);pos=0;if (count < 0)return -1;} if (count > 0){byte b = buf[pos];pos++;count--;return b&0xff;//重点原因，1111-1111 byte大小为-1，与返回值的-1冲突，//因此通过&0xff改变返回值大小，但不改变返回值的最后一个字节}return -1;}public void myClose() throws IOException{is.close();}/*public static void main(String[] args) {System.out.println("Hello World!");}*/}/*sum://函数有返回值//重点原因，1111-1111 byte大小为-1，与返回值的-1冲突，//因此通过&0xff改变返回值大小，但不改变返回值的最后一个字节*///19-15import java.io.*;class  ReadIn{public static void main(String[] args) throws IOException{InputStream is = System.in;//疑问: System.in 是ImputStream 类，是抽象类，为何可以实例化？BufferedInputStream bis = new BufferedInputStream (is);int ch = 0;/*while ((ch = bis.read())!=1){System.out.println(ch);  //用cmd 的ctrl+c 能退出System.in的read。}*/StringBuilder sb = new StringBuilder();while ((ch = bis.read())!=1){if (ch == '\r')continue;if (ch == '\n'){String s = sb.toString();if ("over".equals(s))//equals的用法break;System.out.println(s.toUpperCase());//toUpperCasesb.delete(0,sb.length());//清除String数组}else sb.append((char)ch);}System.out.println("Hello World!");}}/*sum:"over".equals(s)//equals的用法sb.delete(0,sb.length());//清除String数组//疑问: System.in 是ImputStream 类，是抽象类，为何可以实例化？//用cmd 的ctrl+c 能退出System.in的read。s.toUpperCase();//toUpperCase*///19-16_17import java.io.*;import java.util.*;class TransStreamDemo {public static void main(String[] args) throws IOException{/*InputStream is = System.in;InputStreamReader isr = new InputStreamReader(is);//字节流转换字符流BufferedReader br = new BufferedReader (isr);*///System.setIn(new FileInputStream("F:\\t.txt"));//System.setOut(new PrintStream("F:\\t-copy.txt"));//键盘录入常见写法BufferedReader br = new BufferedReader (new InputStreamReader (System.in));BufferedWriter bw = new BufferedWriter (new OutputStreamWriter (System.out));//字符流转化字节流String s = null;while (!(s = br.readLine()).equals("over"))//over可以直接放在这里，这样可以减少代码{//if (s.equals("over"))//break;  bw.write(s);bw.newLine();bw.flush();}System.out.println("Hello World!");br.close();}}/*sum:System.setIn(new FileInputStream("F:\\t.txt"));System.setOut(new PrintStream("F:\\t-copy.txt"));new InputStreamReader(is);//字节流转换字符流new OutputStreamWriter (System.out);//字符流转化字节流FileReader 的编码表是固定的，要用其他的码表就要用InputStreamReader*///19-21import java.io.*;import java.util.*;import java.text.*;class  Exceptioninfo{public static void main(String[] args) {try{int[] arr = new int[2];System.out.println(arr[3]);}catch (Exception e){try{Date d = new Date();SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");String s = sdf.format(d);PrintStream ps = new PrintStream("Exceptioninfo.txt");ps.println(s);//System.setOut(ps);}catch (Exception ex){throw new RuntimeException ("写入失败");}e.printStackTrace(System.out);//}System.out.println("Hello World!");}}/*sum:ps.println(s);e.printStackTrace(System.out);*///log4j 日志工具包

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