多谢你们的解答阿,我是新手,编这个程序费死劲了,现在我的程序是这样,还是出现Exception in thread "main" java.lang.NullPointerException
at GPS.main(GPS.java:111)的错误,我知道是全局变量和局部变量的问题,可怎么改啊,都改了一个小时了。。。。多谢多谢!
public static String getFile(){
String fName = "";
try{
InputStreamReader isr = new InputStreamReader(System.in);
BufferedReader br = new BufferedReader(isr);
System.out.println("Enter the file you want to read");
fName = br.readLine();
}
catch(IOException ioe){
System.err.println("IOException: " + ioe.getMessage());
}
return fName;
}
public static int getCityNum(String fName){
/********** determine how many cities ***********/
int tempCityNumInt = 0;
try {
BufferedReader in=new BufferedReader(
new FileReader(fName));
String tempCityNum=in.readLine();
tempCityNumInt = Integer.parseInt(tempCityNum);
in.close();