输入输出流

JAVA IO
一)File 类是IO类里唯一操作文件类构造方法为: new File(String filePath)
常用的方法: f.exists() f.delete() f.createFile() f.mkdirs() File[] f = f.listFile() –显示文件名和文件路径String[] s = f.list() --- 显示文件名;
二) OutPutStream 字节输出流–抽象类子类：FileOutPutStream -- 一般报异常是FileNotFoundException
OutPutStream outS = new FileOutPutStream(File f);
OutPutStream outS = new FileOutPutStream(File f,Boolean b);
当b =true 时表示在文件末尾追加内容这样前面写的内容任然在.
以下就是字节输出流把字符串文字输出到bfh.txt文件里
String pathname = "e:/bfh.txt ";
File f = new File(pathname);
OutputStream out = new FileOutputStream(f);
String str = "祝贺百均成公司sfq";
byte[] b = str.getBytes(); ---- 字节流只能以字节数组形式输出
try {
out.write(b);
for(int i =0;i<b.length;i++) –每次只写一个
{
out.write(b[i]);
}
} catch (IOException e) {
e.printStackTrace();
}finally{
try {
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
二)InPutStream字节输入流同OutPutStream
InputStream in = new FileInputStream(f);
//byte[] b = new byte[(int)f.length()];
byte[] b = new byte[1024];
try {
in.read();
System.out.println("内容为："+new String(b));
} catch (IOException e) {
e.printStackTrace();
}finally{
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
三) Writer字符输出流是抽象类调用则调用FileWriter 异常是IOException
Writer w = new FileWriter(File f);
Writer w = new FileWriter(File f,Boolean b);
当b=true时在后面追加显示写入的内容
try {
String str = "白福虎sssss";
Writer w = new FileWriter(f);
w.write(str);
w.close();
} catch (IOException e) {
e.printStackTrace();
}
四)Reader 字符输入流同上
Reader r = new FileReader(f);
//char[] c = new char[(char)f.length()];
char[] c = new char[1024];
try {
int len = r.read(c);
r.close();
System.out.println("内容为："+new String(c,0,len));
} catch (IOException e) {
e.printStackTrace();
}
五)字节流和字符流区别
字节主要是读一些如音乐文件、视频文件（可以理解那些比较细腻精度要求高的文件），而字符流就相对宽松一些了：如文本文件……
字符流如果不关闭则需要强制刷新缓存才能把内容输出来out.flush();
以下是一个文件拷贝功能代码
String pathname1 = "e:/sfq.txt";
String pathname2 = "e:/bfh.txt";
File f1= new File(pathname1); //源文件
File f2 = new File(pathname2); //目标文件
if(!f1.exists())
{
System.out.println("源文件不存在!");
System.exit(1);
}
InputStream inPut = new FileInputStream(f1); // 读取源文件里的内容
OutputStream outPut = new FileOutputStream(f2); // 写入目标文件里的内容
if(inPut != null && outPut != null)
{
int temp = 0;
try {
while((temp = inPut.read())!= -1)
{
outPut.write(temp); }
} catch (IOException e) {
e.printStackTrace();
}
}
六) OutputStreamWriter 字符流转向字节流是字符流Writer的子类
InputStreamReader 字节流转向字符流
try {
Writer w = new OutputStreamWriter(new FileOutputStream(f));
Reader r = new InputStreamReader(new FileInputStream(f));
w.write("hello word");
w.flush();
w.close();
char[] c =new char[1024];
int len = r.read(c);
System.out.println(new String(c,0,len));
} catch (IOException e) {
e.printStackTrace();
}
七）BufferedReader 缓存流
Reader r = new InputStreamReader(System.in);
BufferedReader bf = new BufferedReader(r);
String str = "";
try {
str = bf.readLine();
bf.close();
System.out.println(str);
} catch (IOException e) {
e.printStackTrace();
}
八) Scanner 类
九）对象序列化
Java 多线程。