我收到 nullpointerException,不知道到底是什么原因导致的。我从java文档中读到fileinputstream只抛出securityException所以不明白为什么会弹出这个异常。 这是我的代码片段。
private Properties prop = new Properties();
private String settings_file_name = "settings.properties";
private String settings_dir = "\\.autograder\\";
public Properties get_settings() {
String path = this.get_settings_directory();
System.out.println(path + this.settings_dir + this.settings_file_name);
if (this.settings_exist(path)) {
try {
FileInputStream in = new FileInputStream(path + this.settings_dir + this.settings_file_name);
this.prop.load(in);
in.close();
} catch (IOException e) {
e.printStackTrace();
}
} else {
this.create_settings_file(path);
try{
this.prop.load(new FileInputStream(path + this.settings_dir + this.settings_file_name));
}catch (IOException ex){
//ex.printStackTrace();
}
}
return this.prop;
}
private String get_settings_directory() {
String user_home = System.getProperty("user.home");
if (user_home == null) {
throw new IllegalStateException("user.home==null");
}
return user_home;
}
这是我的堆栈跟踪:
C:\Users\mohamed\.autograder\settings.properties
Exception in thread "main" java.lang.NullPointerException
at autograder.Settings.get_settings(Settings.java:41)
at autograder.Application.start(Application.java:20)
at autograder.Main.main(Main.java:19)
Java Result: 1
BUILD SUCCESSFUL (total time: 0 seconds)
Line 41 is: this.prop.load(in);
最佳答案
如果第 41 行是 this.prop.load(in);
那么看起来好像 this.prop == null
在该行添加断点进行验证。
尝试在 null 实例上调用方法会导致 NullPointerException
。
关于java - FileInputStream 抛出 NullPointerException,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/2649073/