We have already introduced Coverity code inspection and related analysis of common high-risk and low-risk logs. Here we mainly look at the analysis of medium-risk logs.
Medium risk (Medium) log analysis
1、Dereference before null check (REVERSE_INULL)
It usually indicates that a null check was reversed in the code, i.e. the object was checked for null before it was used. This error indicates that there is a null value check on the object in the code, and then the object is operated (such as calling a method, accessing a field), which may cause a NullPointerException to occur.
To solve this problem, the following steps can be considered:
1) Examine the part of the code that reports the error, identify the object references involved and reverse the null check operation.
2) Verify that the logic of the null value check is correct, and ensure that the operation on the object is skipped when the object is null.
3) Before performing object operations, use positive null check operations to ensure the non-nullness of the object. This can be achieved using conditional statements (such as if statements) or optional exception handling mechanisms (such as try-catch).
4) Where necessary, additional error handling or logging after the null check may be considered to provide better error context.
Here's an example of how to resolve this error:
public class DereferenceBeforeNullCheckExample {
public static void main(String[] args) {
Object obj = null;
// 错误示例