我试图读取文件,但是我总是会得到nullpointerexception。有人知道可能是什么问题?我在java.io.Reader,java.io.bufferedreader上获得NullPoInterException,lte.hu.eltecom.file.file.file.filemanager.readgraph和elte.hu.eltecom.main.main.main.main
主:
public static void main(String[] args) {
// if (args.length == 0) return;
FileManager fm = new FileManager();
Manager manager;
manager = fm.readGraph("szia");
User user = manager.getUserById(3);
if (user instanceof AdminUser){
((AdminUser) user).kickUser(manager.getUserById(1));
((AdminUser) user).kickUser(manager.getUserById(2));
User grabowski = new User("Grabowski", Language.HUN);
manager.createUser(grabowski);
manager.linkUsers(grabowski,user);
}
fm.writeGraph(manager,args[0]);
}
文件管理器:
static public Manager readGraph(String s) {
FileReader fr = null;
try {
fr = new FileReader(s + "/input.txt");
} catch (FileNotFoundException e) {
}
BufferedReader br = null;
br = new BufferedReader(fr);
String sCurrentLine = null;
try {
sCurrentLine = br.readLine();
} catch (IOException e) {
}
int x = Integer.parseInt(sCurrentLine);
Graph graph = null;
graph = initGraph(x);
Manager manager = null;
manager = new Manager(graph);
int temp = 0;
boolean lineLeft = true;
try {
sCurrentLine = br.readLine();
} catch (IOException e) {
}
User users[] = new User[x];
while(lineLeft){
if (temp < x){
String line[] = sCurrentLine.split(" ", 2);
Language language = Language.valueOf(line[0]);
User user;
String name = line[1];
if (line[1].contains("#")){
name = name.substring(1);
user= manager.createAdminUser(name, language);
}
else{
user = manager.createUser(name, language);
}
users[temp] = user;
}
else {
String line[] = sCurrentLine.split(" ");
for (int i = 0; i < line.length ; i++){
if (Boolean.valueOf(line[i])){
graph.linkNodes(users[temp-x], users[i]);
}
}
}
try {
if ( (sCurrentLine = br.readLine()) == null)
lineLeft = false;
} catch (IOException e) {
}
temp++;
}
return manager;
}
}
在这里看:
try {
fr = new FileReader(s + "/input.txt");
} catch (FileNotFoundException e) {
}
您刚刚写道:"如果找不到文件,请读取文件'任何内容'。此时fr
为null,您将其作为输入传递给BufferedReader
,而无需检查是否为null。
在实例化BufferedReader
之前写一个无用的,或者如果找不到文件,请执行其他操作。
以这种方式忽略异常非常危险,您的代码不会可靠。
另一个建议,String s
的可读性非常差,尝试给出更好的名称(path
或appDir
或任何使读者可以理解的,而无需返回以阅读完整代码)。