帮初学者看一个郁闷的问题！！！！

錯誤太多了,改了一下,能編譯了
import java.io.*;class ReadFromFile {
    public static void main(String args[]) throws FileNotFoundException {
        System.out.println("请输入目录：");        /* 构造带读取文件目录 */
        StringBuffer stfDir = new StringBuffer();        /* 从键盘获取数字 */
        try {
            char aa = (char) System.in.read();
            while (aa != '\n') {
                stfDir.append(aa);            }
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }        File dir = new File(stfDir.toString());        System.out.println("请输入文件名称：");        StringBuffer stfFileName = new StringBuffer();        try {
            char ch = (char) System.in.read();
            while (ch != '\n') {
                stfFileName.append(ch);
            }
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }        /* 创建文件对象 */
        File readFrom = new File(dir, stfFileName.toString());        /* 判断文件是否为目录，具有的权限 */
        try {
            if (readFrom.isFile() && readFrom.canWrite() && readFrom.canRead()) {
                RandomAccessFile rafFile = new RandomAccessFile(readFrom, "rw");                while (rafFile.getFilePointer() < rafFile.length())
                    System.out.println(rafFile.readLine());
                rafFile.close();
            } else {
                System.out.println("文件关闭");            }
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }
    }
}

解决方案 »

免费领取超大流量手机卡，每月29元包185G流量+100分钟通话, 中国电信官方发货

char aa = (char)System.in.read())!='\n'
括号都错了。
这样可以了
关键是：
File dir = new File(stfDir.toString().trim());
要去掉空格，否则显示不出来
import java.io.*;class ReadFromFile
{
public static void main(String args[])
{
char aa;
System.out.println("ÇëÊäÈëÄ¿Â¼£º");

/*¹¹Ôì´ø¶ÁÈ¡ÎÄ¼þÄ¿Â¼*/
StringBuffer stfDir = new StringBuffer();

/*´Ó¼üÅÌ»ñÈ¡Êý×Ö*/
try{
while ((aa=(char)System.in.read())!='\n')
{
stfDir.append(aa);

}
}catch(Exception e){
System.out.println(e);
}

File dir = new File(stfDir.toString().trim());

System.out.println("ÇëÊäÈëÎÄ¼þÃû³Æ£º");

StringBuffer stfFileName = new StringBuffer();

char ch;

try{
while((ch=(char)System.in.read())!='\n')
{
stfFileName.append(ch);
}
}catch(Exception e){
System.out.println(e);
}

/*´´½¨ÎÄ¼þ¶ÔÏó*/
File readFrom = new File(dir,stfFileName.toString().trim());

/*ÅÐ¶ÏÎÄ¼þÊÇ·ñÎªÄ¿Â¼£¬¾ßÓÐµÄÈ¨ÏÞ*/
try{
if(readFrom.isFile() &&  readFrom.canWrite() && readFrom.canRead())
{
RandomAccessFile rafFile = new RandomAccessFile(readFrom,"rw");

while(rafFile.getFilePointer()<rafFile.length())
System.out.println(rafFile.readLine());
rafFile.close();
}else{
         System.out.println("ÎÄ¼þ¹Ø±Õ");

    }
}catch(Exception e){
System.out.println(e);
}
}
}