IO流1 --- File类的实例化 --- 技术搬运工（尚硅谷）

• 构造器1 File(String pathname)

//相对路径
File file1 = new File("hello.txt");
//windows绝对路径
File file2 = new File("C:\\Users\\Mi\\Documents\\project\\idea\\JavaBase\\hello.txt");
//路径分隔符
String separator = File.separator;

• 构造器2 File(String parent, String child)

File file3 = new File("C:\\Users\\Mi\\Documents\\project\\idea","JavaBase");

• 构造器3 File(File parent, String child)

File file3 = new File("C:\\Users\\Mi\\Documents\\project\\idea","JavaBase");
File file4 = new File(file3,"hello.txt");