File类：
对硬盘上的文件和目录进行操作的类。
构造函数：
1） File(String pathname)
Creates a new File instance by converting the given pathname string into an abstract pathname.
2）File(File parent, String child)
Creates a new File instance from a parent abstract pathname and a child pathname string.
3）File(String parent, String child)
Creates a new File instance from a parent pathname string and a child pathname string.
4）File(URI uri)
Creates a new File instance by converting the given file: URI into an abstract pathname.
方法：
1） list()
Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname.
2） list(FilenameFilter filter)
Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.
3） listFiles()
Returns an array of abstract pathnames denoting the files in the directory denoted by this abstract pathname.
4） listFiles(FileFilter filter)
Returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.
5） listFiles(FilenameFilter filter)
Returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.
6） Boolean createNewFile()
Atomically creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist.
7） mkdir()
Creates the directory named by this abstract pathname.
8） static File createTempFile(String prefix, String suffix)
Creates an empty file in the default temporary-file directory, using the given prefix and suffix to generate its name.
演示：
File path = new File(“icons”);
try {
//创建文件和目录
path.mkdir();
File.createTempFile(“temp”,”.java”,path);
} catch (IOException e) {
System.out.println(“创建临时文件异常:= ” +e.getMessage());
}
File f = new File(“.”);
File[] fileList = f.listFiles();
for(int i = 0; i < fileList.length;i++){
if(fileList[i].isDirectory()){
System.out.println(“目:= ” + fileList[i].getAbsolutePath());
}else{
System.out.println(“文:= ” + fileList[i].getAbsolutePath());
}
}
//筛选文件
String[] fileNames = f.list(new FilterNames());
for(int i = 0; i < fileNames.length;i++){
System.out.println(“名称为:= ” + fileNames[i]);
}
IO流：
流的分类：
1）节点流：应用程序直接操作目标设备所对应的流，只能操作字节字符型数据。
字节流
InputStream
OutputStream
字符流
2）包装流：提供了应用程序与外部设备之间，各种类型数据的读写功能。
对文件操作的流：
FileInputStream
FileOutputStream
FileReader
FileWriter
Reader
Writer
RandomAccessFile
RandomAccess
演示：
File f = new File(“configuration.txt”);
InputStream in = null;
OutputStream out = null;
String data = “世界和平是任何力量阻挡不了的” + System.getProperty(“line.separator”);
//调用系统的换行方式,在windows中使用’\r\n’
写入
try {
out = new FileOutputStream(f,true); //追加在文件的末尾的方法
out.write(data.getBytes());
out.close();
} catch (IOException e) {
System.out.println(“写文件数据异常:= ” + e.getMessage());
}
try{
in = new FileInputStream(f);
byte[] buff = new byte[102];
int len;
while((len = in.read(buff)) != -1){
System.out.println(“len:= ” + len);
System.out.println(new String(buff,0,len));
}
in.close();
}catch(IOException e){
System.out.println(“读取文件数据异常:= ” + e.getMessage());
}