Java.lang.nullpointerexception: file download manager

Viewed 1k times. URL is invalid. I have the following exception java. NullPointerException at xk. Improve this question. Thank u for telling me that! Add a comment. Active Oldest Votes. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. I am unable to properly add new boards under the board manager which states java. NullPointException in red along the bottom of the window and outputs this:.

I am running Arduino 1. I was using the IDE this morning and just went to use it again and now I am getting this issue. Edit: Tested this out on my laptop also which hasn't been updated currently running 1. The text was updated successfully, but these errors were encountered:. Sorry, something went wrong. Same root cause as , , and While it was working perfectly on TWO systems as recently as 13 hours ago, neither are working now.

A bad json file released today on arduino. Think I have a related issue where the IDE fails to start and dies on loading packages. I deleted the Arduino15 the IDE 1. It usually pop up when we least expect them. I have also spent a lot of time while looking for reasons and the best approaches to handle null issues. I will be writing here some of the best practices followed industry-wise, sharing some expert talks and my own learning over time.

NullPointerException is a runtime condition where we try to access or modify an object which has not been initialized yet. In the given example, String s has been declared but not initialized. When we try to access it in the next statement s.

Well, NullPointerException can occur anywhere in the code for various reasons but I have prepared a list of the most frequent places based on my experience. This is not an exhaustive list. There are several other places and reasons also. If you can recall any such other, please leave a comment. Ternary operator results in the value on the left-hand side if not null else right-hand side is evaluated.

It has syntax like :. If the expression is evaluated as true then the entire expression returns value1 otherwise value2. It is more like an if-else construct but it is more effective and expressive. Apache Commons Lang is a collection of several utility classes for various kinds of operation. One of them is StringUtils. We should always do the method input validation at the beginning of the method so that the rest of the code does not have to deal with the possibility of incorrect input.

Therefore if someone passes in a null as the method argument, things will break early in the execution lifecycle rather than in some deeper location where the root problem will be rather difficult to identify.

A null problem occurs where object references point to nothing. So it is always safe to use primitives. Consider using primitives as necessary because they do not suffer from null references. A single statement spread over several lines will give you the line number of the first line in the stack trace regardless of where it occurs.

It really is hard to debug such code. Avoid such calls if possible. If we have to print the string representation of any object, then consider not using toString method. This is a very soft target for NPE. Instead use String. An awesome tip to avoid NPE is to return empty strings or empty collections rather than null. Java 8 Optionals are a great alternative here. Do this consistently across your application.

You will note that a bucket load of null checks becomes unneeded if you do so. Users of the above method, even if they missed the null check, will not see the ugly NPE. I have seen some method declarations where the method expects two or more parameters. If one parameter is passed as null, then also method works in a different manner. This is to ensure that code granted that permission such as the JDK itself is allowed to manipulate any thread.

If this method is overridden, then super. Parameters: t - the thread to be checked. Throws: SecurityException - if the calling thread does not have permission to modify the thread.

NullPointerException - if the thread argument is null. This method is invoked for the current security manager when a new child thread or child thread group is created, and by the setDaemon , setMaxPriority , stop , suspend , resume , and destroy methods of class ThreadGroup. If the thread group argument is the system thread group has a null parent then this method calls checkPermission with the RuntimePermission "modifyThreadGroup" permission.

If the thread group argument is not the system thread group, this method just returns silently. If this method is overridden, the method that overrides it should additionally check to see if the calling thread has the RuntimePermission "modifyThreadGroup" permission, and if so, return silently. Parameters: g - the thread group to be checked. Throws: SecurityException - if the calling thread does not have permission to modify the thread group.

NullPointerException - if the thread group argument is null. This method is invoked for the current security manager by the exit method of class Runtime. A status of 0 indicates success; other values indicate various errors. Parameters: status - the exit status. Throws: SecurityException - if the calling thread does not have permission to halt the Java Virtual Machine with the specified status.

This method is invoked for the current security manager by the exec methods of class Runtime. Parameters: cmd - the specified system command. Throws: SecurityException - if the calling thread does not have permission to create a subprocess. NullPointerException - if the cmd argument is null. See Also: Runtime. String , Runtime. String, java. String[] , Runtime. String[], java. The argument is either a simple library name or a complete filename. This method is invoked for the current security manager by methods load and loadLibrary of class Runtime.

This method calls checkPermission with the RuntimePermission "loadLibrary. Parameters: lib - the name of the library. Throws: SecurityException - if the calling thread does not have permission to dynamically link the library. NullPointerException - if the lib argument is null. Parameters: fd - the system-dependent file descriptor. Throws: SecurityException - if the calling thread does not have permission to access the specified file descriptor.

NullPointerException - if the file descriptor argument is null. This method calls checkPermission with the FilePermission file,"read" permission. Parameters: file - the system-dependent file name. Throws: SecurityException - if the calling thread does not have permission to access the specified file.

NullPointerException - if the file argument is null. The context must be a security context returned by a previous call to getSecurityContext. Parameters: file - the system-dependent filename. This method calls checkPermission with the FilePermission file,"write" permission. This method is invoked for the current security manager by the delete method of class File.

This method calls checkPermission with the FilePermission file,"delete" permission. Throws: SecurityException - if the calling thread does not have permission to delete the file. See Also: File. A port number of -1 indicates that the calling method is attempting to determine the IP address of the specified host name.

If the port is equal to -1, then it calls checkPermission with the SocketPermission host,"resolve" permission. Parameters: host - the host name port to connect to.

Throws: SecurityException - if the calling thread does not have permission to open a socket connection to the specified host and port. NullPointerException - if the host argument is null. Otherwise, the port number is checked. If the port is equal to -1, then the context 's checkPermission method is called with a SocketPermission host,"resolve" permission.

Parameters: port - the local port. Throws: SecurityException - if the calling thread does not have permission to listen on the specified port. This method is invoked for the current security manager by the accept method of class ServerSocket.