结构: Simple
Abstraction: Variant
状态: Incomplete
被利用可能性: unkown
The program compares object references instead of the contents of the objects themselves, preventing it from detecting equivalent objects.
For example, in Java, comparing objects using == usually produces deceptive results, since the == operator compares object references rather than values; often, this means that using == for strings is actually comparing the strings' references, not their values.
Language: [{'cwe_Name': 'Java', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Name': 'JavaScript', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Name': 'PHP', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Class': 'Language-Independent', 'cwe_Prevalence': 'Undetermined'}]
范围 | 影响 | 注释 |
---|---|---|
Other | Varies by Context | This weakness can lead to erroneous results that can cause unexpected application behaviors. |
策略:
In Java, use the equals() method to compare objects instead of the == operator. If using ==, it is important for performance reasons that your objects are created by a static factory, not by a constructor.
In the example below, two Java String objects are declared and initialized with the same string values and an if statement is used to determine if the strings are equivalent.
bad Java
However, the if statement will not be executed as the strings are compared using the "==" operator. For Java objects, such as String objects, the "==" operator compares object references, not object values. While the two String objects above contain the same string values, they refer to different object references, so the System.out.println statement will not be executed. To compare object values, the previous code could be modified to use the equals method:
good
In the following Java example, two BankAccount objects are compared in the isSameAccount method using the == operator.
bad Java
Using the == operator to compare objects may produce incorrect or deceptive results by comparing object references rather than values. The equals() method should be used to ensure correct results or objects should contain a member variable that uniquely identifies the object.
The following example shows the use of the equals() method to compare the BankAccount objects and the next example uses a class get method to retrieve the bank account number that uniquely identifies the BankAccount object to compare the objects.
good Java
映射的分类名 | ImNode ID | Fit | Mapped Node Name |
---|---|---|---|
The CERT Oracle Secure Coding Standard for Java (2011) | EXP02-J | Use the two-argument Arrays.equals() method to compare the contents of arrays | |
The CERT Oracle Secure Coding Standard for Java (2011) | EXP02-J | Use the two-argument Arrays.equals() method to compare the contents of arrays | |
The CERT Oracle Secure Coding Standard for Java (2011) | EXP03-J | Do not use the equality operators when comparing values of boxed primitives |