java笔记（一）Io

File
文件的创建
String path = "D:"+File.separator+"text"+File.separator+"test.text";
File f = new File(path);
try {
f.createNewFile( );
} catch (Exception e) {
e.printStackTrace();

}

//删除文件
if(f.exists()){//判断文件是否存在
f.delete();
}

//创建文件夹
File fdir = new File("D:"+File.separator+"文件夹");
fdir.mkdir();//创建文件夹
fdir.delete();//删除文件夹

//列出文件夹的内容
File flist = new File("D:"+File.separator);
String[] list1 = flist.list();
File[] list2 = flist.listFiles();
for(int i=0;i<list1.length;i++){
System.out.println(list1[i]);//只列出文件名
}
for(int i=0;i<list2.length;i++){
System.out.println(list2[i]);//列出完整的路径
}

//判断是不是文件夹
if(flist.isDirectory()){
System.out.print("文件夹");
}else{
System.out.print("不是文件夹");
}

字节流

输出字节流

File f = new File("d:"+File.separator+"text"+File.separator+"test1.text");//OutputStream out = new FileOutputStream(f);//文件存在就自动创建OutputStream out = new FileOutputStream(f,true);//加上ture后表示追加String n = "\r\nwo shi haoren好人";//\r\n表示换行byte[] b = n.getBytes();//out.write(b);out.close();

输出字节流

File f = new File("d:"+File.separator+"text"+File.separator+"test1.text");//OutputStream out = new FileOutputStream(f);//文件存在就自动创建OutputStream out = new FileOutputStream(f,true);//加上ture后表示追加byte[] b = n.getBytes();//(int) f.length()用来确定接收数组的长度//第一种方式//out.write(b);//第二种方式for(int i=0;i<b.length;i++){out.write(b[i]);}in.close();System.out.print(new String(b));

输入字节流

File f = new File("d:"+File.separator+"text"+File.separator+"test1.text");InputStream in = new FileInputStream(f);byte[] b = new byte[(int) f.length()];//(int) f.length()用来确定接收数组的长度//第一种读入方式//in.read(b);// int l = in.read(b);in.close();System.out.print(new String(b));System.out.println(new String(c,0,l));//这里必须要限定长度，不然要出乱码

另外两种读入方式

File f = new File("d:"+File.separator+"text"+File.separator+"test1.text");InputStream in = new FileInputStream(f);byte[] b = new byte[(int) f.length()];//(int) f.length()用来确定接收数组的长度//第二种读入方式/*for(int i=0;i<b.length;i++){b[i] = (byte)in.read();}*///第三种方式int i = 0;int temp =0;while((temp = in.read())!=-1 ){//当值为-1时，就表示读到文件的末尾b[i] = (byte)temp;i++;}in.close();System.out.print(new String(b));}

字符流
输出字符流

File f = new File("d:"+File.separator+"text"+File.separator+"test2.text");Writer out = new FileWriter(f,true);String t = "\r\n我爱我的祖国";out.write(t);out.close();

输入字符流

FileReader in = new FileReader(f);char[] c = new char[(int)f.length()];//第一种方式//int l=in.read(c);//第二种方式int temp;int l = 0;while((temp = in.read()) != -1){c[l] = (char)temp;l++;}

字节流和字符流的区别
字符流使用了缓冲区（即内存中的一块区域），可以用不关闭流，看是否会写到文件中为例来证明。
out.flush():强制清空缓冲区，这样在不关闭字符流的情况下也可以将数据写入到文件中。
在开发中字节流使用较多

内存操作流

String t = "woshihaoren";//通过ByteArrayInputStream的构造方法向内存写入数据ByteArrayInputStream bis = new ByteArrayInputStream(t.getBytes());//创建读内存的流ByteArrayOutputStream bos = new ByteArrayOutputStream();int temp=0;while((temp = bis.read()) != -1){//注意这里是bis.read(),而不是bos.read()char c = (char) temp;bos.write(Character.toUpperCase(c));}System.out.print(bos.toString());bis.close();bos.close();

转换流

//将输出的字符流转化为字节流OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream(f));String t = "woshihaoren";osw.write(t);osw.close();//将输入的字节流转化为字符流InputStreamReader isw = new InputStreamReader(new FileInputStream(f));char[] c = new char[(int)f.length()];int n = isw.read(c);isw.close();System.out.println(new String(c,0,n));

管道流

public static void main(String[] args) {Person p = new Person();Spook s = new Spook();try {p.getPos().connect(s.getPis());} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}new Thread(p).start();new Thread(s).start();}//发送端class Person implements Runnable{private PipedOutputStream pos= null;public  Person(){pos = new PipedOutputStream();}public void run() {String l = "wo shi haoren";pos.write(l.getBytes());pos.close();}public PipedOutputStream getPos(){return pos;}}//接收端class Spook implements Runnable{PipedInputStream pis = null;public Spook() {this.pis = new PipedInputStream();}public void run() {byte[] b = new byte[1024];int length = 0;length = pis.read(b);pis.close();System.out.print(new String(b,0,length));}public PipedInputStream getPis(){return pis;}}

打印流(分为字节打印流和字符打印流)

File f = new File("d:"+File.separator+"text"+File.separator+"test6.text");//字节打印流PrintStream ps = new PrintStream(new FileOutputStream(f));ps.print("我是好人");ps.print("我是好人aasdsad");//字符打印流PrintWriter pw  = new PrintWriter(new FileWriter(f));pw.print("haoren");pw.close();

打印流的格式化输出

File f = new File("d:"+File.separator+"text"+File.separator+"test6.text");PrintStream ps = new PrintStream(new FileOutputStream(f));PrintWriter pw  = new PrintWriter(new FileWriter(f));String name = "张三";int age = 20;double score = 89.7;char sex = 'F';//字节打印流格式化输出//ps.printf("name:%s,age:%d,score:%f,sex:%c",name,age,score,sex);//ps.close();//字符打印流格式化输出pw.printf("name:%s,age:%d,score:%f,sex:%c",name,age,score,sex);pw.close();