Possible null access due to exception handling JAVA-E1084

This code contains a possible null dereference that may occur based on whether an exception is thrown or not. Carefully check your code to ensure that the concerned value can never be null at this point.

Bad Practice

In the snippet below, whether the value of s stays null depends on whether mayThrow() throws an exception. If an exception were thrown, the code would skip the assignment to s, which means it would remain as null until it is accessed for a method call. This will lead to a NullPointerException being thrown.

String s = null;

try {
    mayThrow();

    s = "SomeValue";
} catch (SomeException e) {
    // no assignment of s
}

int len = s.length; // This will be null if the method call throws!

Recommended

This could be fixed either by performing a check at the usage site, if the logic requires that s should possibly be null:

int len = (s == null) ? 0 : s.length();

It could also be fixed by changing the preceding logic to correctly set the value of s at all points. For example, the catch block could set s to a safe default value:

try {
    // ...
} catch (SomeException e) {
    s = "";
}

int len = s.length; // no exception!

References

• CWE-476 - Null Pointer Dereference