File:是文件和路径名的抽象表示
文件和目录可以通过File封装成对象
File(String pathname)
File(String parent,String child)
File(File parent,String child)
File f1 = new File("D:\\FileTest\\f1.txt");
System.out.println(f1);//D:\FileTest\f1.txt
File f2 = new File("D:\\FileTest","f1.txt");
System.out.println(f2);//D:\FileTest\f1.txt
File f3 = new File(new File("D:\\FileTest"),"f1.txt");
System.out.println(f3);//D:\FileTest\f1.txt