FileInputStream fi=new FileInputStream("D:\\javaproject\\lianxi\\123.txt");     //第一种
FileInputStream fi=new FileInputStream("D:/javaproject/lianxi/123.txt");       //第二种

FileInputStream fi=new FileInputStream("D:\\javaproject\\lianxi\\123.txt");     //第一种
FileInputStream fi=new FileInputStream("D:/javaproject/lianxi/123.txt");       //第二种